This disclosure relates to silicon-containing compounds, to methods of their preparation, and to their use in fragrances.

Green odorants are important for providing contrast and freshness to perfumery compositions, especially masculine fragrances. Particularly useful are odorants with a galbanum profile that proves particularly useful for this purpose. The typical galbanum odor profile is characterized as intensely green, vegetal-sulfurous, metallic. In addition, many of the typical galbanum odorants have a prominent pineapple character and a distinct floral side recalling hyacinths and/or violet flowers.

Sila-substitution of carbon atoms in organic compounds elongates a Si-C bond by ca. 20% as compared to a C-C bond, increases the van-der-Waals volume, as for instance from 86.3 A for a -CMe ₃ group to 96.8 A for a -SiMe ₃ group, and also increases the mass of the sila-compounds as silicon is more than twice the mass of carbon. These structural differences often have considerable and unpredictable effects on the properties of sila-substituted compounds as compared with their carbon counterparts (R. Tacke, S. Metz in 'Current Topics in Flavor and Fragrance Research', VHCA/Wiley-VCH, Zurich/Weinheim, 2008, p. 83-104).

Surprisingly it has now been found that in the case of 5,5-dialkyl-substituted or 5,5-spiro-annulated 1 -(cyclohex-1 -en-1 -yl)pent-4-en-1 -ones the desired fresh galbanum character is maintained in 5- sila-substituted analogues, while the less desirable floral aspects of the parent carbon compounds that recall hyacinths and/or violet flowers are absent. Furthermore these new and novel 5-sila- substituted 5,5-dialkyl-substituted and 5,5-spiro-annulated 1 -(cyclohex-1 -en-1 -yl)pent-4-en-1-ones possess superior substantivity in functional applications in comparison with related carbon structures.

There is therefore provided a chemical compound of the formula I

in which R and R ² are independently selected from C-|-C ₃ alkyl, or R and R ² together with the silicon atom to which they are joined to form a 5 to 6 membered ring, the ring, apart from the silicon atom, consisting completely of carbon and hydrogen atoms.

In a particular embodiment, R and R ² are both methyl groups.

In a further particular embodiment, R and R ² together with the silicon atom form a five-membered ring, to provide a compound of the formula II:

Surprisingly, the sila-substitution results in galbanum odorants free from floral facets that are more substantive in functional applications. In addition, an industrially attractive route to prepare these compounds has been found. This is achieved by hydroformylation of divinylsilanes, such as dialkyldivinylsilane, in which the alkyl groups are independently C C ₃ alkyl, and particularly both methyl, dichlorodivinylsilane, 1 ,1-divinylsilolane and 1 ,1-divinylsilinane, with subsequent aldol condensation and incorporation of the homoallyl side chain by using a Grignard reagent and oxidation of the resulting alcohols to the α,β-unsaturated ketones. This process allows the synthesis of compounds of formula I free from any double bond isomers in the ring that are weaker or possess unattractive side notes. As dialkyldivinylsilane and dichlorodivinylsilane are comparatively inexpensive building blocks, this route allows not only for the easy industrial synthesis of the desirable fragrance compounds I, but also considerably reduces cost.

Thus, a typical method for the preparation of a compound of the formula I, in which R and R ² are both methyl, is illustrated in Scheme I:

A typical method for the preparation of a compound of formula II is shown in Scheme II:

Scheme II

The compounds of formula I possess fresh green, galbanum-type odor characteristics free from floral hyacinth and violet odor characteristics, and have been found to be useful in the preparation of fragrance compositions. By "fragrance composition" is meant any composition comprising at least one compound of formula I and a base material, e.g. a diluent conventionally used in conjunction with odorants, such as dipropyleneglycol (DPG), isopropyl myristate (IPM), triethylcitrate (TEC), and alcohol (e.g. ethanol).

The compounds may be combined with one or more of the many fragrance molecules and substances known to and used by the art to provide a fragrance composition. There is therefore also provided a fragrance composition comprising at least one fragrance ingredient and at least one compound as hereinabove defined. Typical non-limiting examples of such fragrance ingredients include - essential oils and extracts, e.g. castoreum, costus root oil, oak moss absolute, geranium oil, tree moss absolute, basil oil, fruit oils such as bergamot oil and mandarin oil, galbanum oil, myrtle oil, palmarose oil, patchouli oil, petitgrain oil, jasmine oil, rose oil, sandalwood oil, wormwood oil, lavender oil or ylang-ylang oil;

- alcohols, e.g. cinnamic alcohol, c/s-3-hexenol, citronellol, Ebanol™, eugenol, farnesol, geraniol, Super Muguet™, linalool, menthol, nerol, phenylethyl alcohol, rhodinol, Sandalore™, terpineol or Timberol™;

- aldehydes and ketones, e.g. Azurone ^® (7-(3-methylbutyl)-1 ,5-benzodioxepin-3-one),

anisaldehyde, a-amylcinnamaldehyde, Dynasone, Galbanone, Georgywood™, hydroxycitronellal, Iso E ^® Super, Isoraldeine ^® , Hedione ^® , Lilial ^® , maltol, methyl cedryl ketone, methylionone, Neobutenone, verbenone or vanillin;

- ethers and acetals, e.g. Ambrox™, geranyl methyl ether, rose oxide or Spirambrene™;

- esters and lactones, e.g. benzyl acetate, Cedryl acetate, γ-decalactone, Helvetolide ^® ,

γ-undecalactone or vetivenyl acetate;

- macrocycles, e.g. Ambrettolide, ethylene brassylate or Exaltolide ^® ;

- heterocycles, e.g. isobutylquinoline.

The compounds according to formula I and fragrance compositions containing them may be used in a broad range of fragrance applications, for example, in any field of fine and functional perfumery, such as perfumes, air care products, household products, laundry products, body care products and cosmetics. The compounds can be employed in widely varying amounts, depending upon the specific application and on the nature and quantity of other odorant ingredients. The proportion is typically from 0.05 to 10 weight percent of the application. In one embodiment, compounds of the present invention may be employed in a fabric softener in an amount of from 0.005 to 0.5 weight per cent. In another embodiment, compounds of the present invention may be used in fine perfumery in amounts of from 0.05 to 10 weight per cent (e.g. up to about 5 weight per cent), more preferably between 0.01 and 5 weight per cent. However, these values are given only by way of example, as the experienced perfumer may also achieve effects or may create novel accords with lower or higher concentrations.

The compounds as described hereinabove may be employed in a consumer product base simply by directly mixing at least one compound of formula I, or a fragrance composition with the consumer product base. By "consumer product base" is meant the totality of all of the standard ingredients apart from fragrance required to make the consumer product. These may be used in art-recognised concentrations. Their natures may change with application, but non-limiting examples include surfactants and emulsifiers, solvents, colouring matters and dyestuffs, rheology and flow control agents, extenders, abrasives, optical brighteners and fluorescing agents

The compounds may be employed in their normal state, or they may be employed in entrapped or encapsulated form. Examples of such forms include polymers, capsules, microcapsules and nanocapsules, liposomes, film formers, absorbents such as carbon or zeolites, cyclic

oligosaccharides and mixtures thereof, or by chemically bonding to substrates, which are adapted to release the fragrance molecule upon application of an external stimulus such as light, enzyme, or the like, and then mixed with the consumer product base.

Thus, there is additionally provided a method of manufacturing a fragrance application, comprising the incorporation of a compound of formula I, as a fragrance ingredient, either by directly admixing the compound to the consumer product base or by admixing a fragrance composition comprising a compound of formula I, which may then be mixed with a consumer product base, using conventional techniques and methods. Through the addition of an olfactory acceptable amount of at least one compound of the present invention as hereinabove described the odour notes of a consumer product base will be improved, enhanced or modified.

Thus, there is provided a method for improving, enhancing or modifying a consumer product base by means of the addition thereto of an olfactorily acceptable amount of at least one compound of formula I.

The invention also provides a fragrance application comprising:

a) as odorant at least one compound of formula I; and

b) a consumer product base.

As used herein, "consumer product base" means a composition for use as a consumer product to fulfil specific actions, such as cleaning, softening, and caring or the like. Examples of such products include fine perfumery, e.g. perfume and eau de toilette;

fabric care, household products and personal care products such as laundry care detergents, rinse conditioner, personal cleansing composition, detergent for dishwasher, surface cleaner; laundry products, e.g. softener, bleach, detergent; body-care products, e.g. shampoo, shower gel; air care products and cosmetics, e.g. deodorant, vanishing cream. This list of products is given by way of illustration and is not to be regarded as being in any way limiting.

The disclosure is further exemplified with reference to the following non-limiting examples, which depict preferred embodiments.

Example 1 : 1 -(5,5-Dimethyl-5-silacyclohex-1 -en-1 -yl)pent-4-en-1 -one A 1 .6 M solution of vinyl magnesium chloride (1 .07 I, 1 .71 mol of CH ₂ =CHMgCI) was added dropwise at 0 °C within 3 h to a stirred solution of dichlorodimethylsilane (200 g, 1 .55 mol) in diethyl ether (600 ml), and the resulting mixture was then heated under reflux for 2 h. The mixture was allowed to cool to 20 °C within 30 min, water (500 ml) was added, the organic phase was separated, the aqueous phase was extracted with diethyl ether (5 100 ml) and discarded, and the combined organic solutions were dried over anhydrous sodium sulfate. The solvents were removed by distillation at atmospheric pressure using a spinning band column, and the residue was then purified by a further distillation at atmospheric pressure with a spinning band column to furnish dimethyldivinylsilane as a colourless liquid (150 g, 1 .34 mol; 86% yield). B.p. 78 °C; H NMR (500.1 MHz, C ₆ D ₆ ): δ = 0.24 (s, 6 H; CH ₃ ), 5.83 (6 _A ), 6.06 (6 _B ), 6.28 ppm (6 _C ) (ABC system, ² J(A,B) = 3.8, ³ J(A,C) = 20.3, ³ J(B,C) = 14.7 Hz, 6 H; CH _C =CH _A H _B ); ³ C NMR (125.8 MHz, C ₆ D ₆ ): δ = -3.2 (CH ₃ ), 132.5 (CH ₂ ), 138.1 ppm (CH); ²⁹ Si NMR (99.4 MHz, C ₆ D ₆ ): δ = -13.8 ppm; elemental analysis calcd (%) for C ₆ H ₁₂ Si: C 64.20, H 10.78; found: C 64.27, H 10.79.

A mixture of dimethyldivinylsilane (5.00 g, 44.5 mmol), triphenylphosphine (584 mg, 2.23 mmol), (acetylacetonato)dicarbonylrhodium(l) (80 mg, 310 μιηοΙ), and benzene (30 ml) was heated in an autoclave at 80 °C for 7 h under an atmosphere of hydrogen (45 bar) and carbon monoxide (45 bar) and was then allowed to cool to 20 °C within 30 min. The mixture was filtered through a pad of silica gel (30 g), followed by elution with n-hexane/diethyl ether (9:1 v/v). The solvent of the filtrate (including the eluate) was removed under reduced pressure (5 mbar), and the residue was suspended in a mixture of diethyl ether (50 ml) and water (50 ml). The organic phase was separated, the aqueous phase was extracted with diethyl ether (3 ^χ 30 ml) and discarded, and the combined organic solutions were dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure (5 mbar), the residue was purified by a rapid bulb-to-bulb distillation (oven temperature 150 °C, 0.01 mbar), and the distillate was then further purified by a second bulb-to- bulb distillation (oven temperature 95 °C, 0.01 mbar) to furnish 3,3 ^' -(dimethylsilanediyl)dipropanal as a colourless liquid (1 .30 g, 7.55 mmol; 17% yield). H NMR (500.1 MHz, C ₆ D ₆ ): δ = -0.14 (6 H; CH ₃ ), 0.53 (6AA ), 1 .91 (6 _DD ), 9.46 ppm (6 _X ) (AA ^' DD ^' X system, ² J(A,A ^' ) = 17.1 , ² J(D,D ^' ) = 14.4, ³ J(A,D) = ³ J(A ^' ,D ^' ) = 5.5, ³ J(A,D ^' ) = ³ J(A ^' ,D) = 1 1 .0, ³ J(D,X) = ³ J(D ^' ,X) = 1 .5 Hz, 10 H;

CH _A H _A CH _D H _D CH _X ); ³ C NMR (125.8 MHz, C ₆ D ₆ ): δ = -3.9 (CH ₃ ), 6.4 (SiCH ₂ ), 38.0 (CH ₂ CH), 200.9 ppm (CHO); ²⁹ Si NMR (99.4 MHz, C ₆ D ₆ ): δ = 4.3 ppm; elemental analysis calcd (%) for C ₈ H ₁₆ 0 ₂ Si: C 55.77, H 9.36; found: C 55.60, H 9.55.

A mixture of dimethyldivinylsilane (15.3 g, 136 mmol), triphenylphosphine (1 .80 g, 6.86 mmol), (acetylacetonato)dicarbonylrhodium(l) (246 mg, 953 μιηοΙ), and benzene (50 ml) was heated in an autoclave at 80 °C for 7 h under an atmosphere of hydrogen (45 bar) and carbon monoxide (45 bar) and was then allowed to cool to 20 °C within 30 min. The resulting mixture [containing the intermediate 3,3 ^' -(dimethylsilanediyl)dipropanal] was then added dropwise at 0°C within 1 h to a stirred 0.5 M solution of hydrogen chloride in diethyl ether (400 ml, 200 mmol of HCI), and the resulting mixture was then kept undisturbed at 20 °C for 18 h. The mixture was filtered through a pad of silica gel (180 g), followed by elution with n-hexane/diethyl ether (1 : 1 v/v). The solvent of the filtrate (including the eluate) was removed under reduced pressure, and the residue was purified by flash chromatography on silica gel (eluent, n-hexane/diethyl ether (8:2 v/v)), followed by bulb-to- bulb distillation (oven temperature 70 °C, 0.01 mbar) to furnish 5,5-dimethyl-5-silacyclohex-1 -ene- 1 -carbaldehyde as a colourless liquid (7.50 g, 48.6 mmol; 36% yield). H NMR (500.1 MHz, C ₆ D ₆ ): 6 = -0.02 (6 H; CH ₃ ), 0.51 (6AA ), 1 .54 (6 _DD ), 2.17 (6 _HH ), 6.20 (6 _X ) (AA ^' DD ^' HH ^' X system, ² J(A,A ^' ) = 12.4, ² J(D,D ^' ) = 12.4, ² J(H,H ^' ) = 15.2, ³ J(A,H) = ³ J(A ^' ,H ^' ) = 7.5, ³ J(A,H ^' ) = ³ J(A ^' ,H) = 6.3, ³ J(H,X) = ³ J(H ^' ,X) = 4.8, ⁴ J(D,X) = ⁴ J(D ^' ,X) = 1 .5, ⁵ J(D,H) = ⁵ J(D ^' ,H ^' ) = 2.0, ⁵ J(D,H ^' ) = ⁵ J(D ^' ,H) = 1 .4 Hz, 7 H; SICHAHA CHHHH CH _X =CCH _D H _D ), 9.45 ppm (CHO); ³ C NMR (125.8 MHz, C ₆ D ₆ ): δ = -3.0 (CH ₃ ), 8.4 (C-6), 9.4 (C-4), 21 .1 (C-3), 141 .2 (C-1 ), 152.4 (C-2), 194.0 ppm (CHO); ²⁹ Si NMR (99.4 MHz, C ₆ D ₆ ): δ = -3.6 ppm ; elemental analysis calcd (%) for C ₈ H ₁₄ OSi : C 62.28, H 9.15; found: C 62.15, H 9.15. Odor description: cuminic, aniseed-like, pungent.

4-Bromo-1 -butene (1 1 .4 g, 84.4 mmol) was added dropwise within 30 min to a suspension of magnesium turnings (2.60 g, 107 mmol) in diethyl ether (130 ml), causing the reaction mixture to boil under reflux. The mixture was heated under reflux for a further h, allowed to cool to 20 °C within 20 min, and then added dropwise at -10 °C within 30 min to a stirred solution of 5,5- dimethyl-5-silacyclohex-1 -ene-1 -carbaldehyde (8.70 g, 56.4 mmol) in diethyl ether (180 ml). The resulting mixture was allowed to warm to 20 °C within 30 min and was then stirred at this temperature for a further h, a saturated aqueous solution of ammonium chloride (150 ml) was added, the organic phase was separated, the aqueous phase was extracted with diethyl ether (3 x 100 ml) and discarded, and the combined organic solutions were dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure, and the residue was purified by flash chromatography on silica gel (eluent, n-hexane/diethyl ether (7:3 v/v)), followed by bulb-to-bulb distillation (oven temperature 130 °C, 0.01 mbar) to furnish 1 -(5,5-dimethyl-5-silacyclohex-1 -en-1 - yl)pent-4-en-1 -ol as a colourless liquid (10.9 g, 51 .8 mmol; 92% yield). H NMR (500.1 MHz, C ₆ D ₆ ): 6 = 0.1 1 (s, 3 H; CH ₃ ), 0.13 (s, 3 H; CH ₃ ), 0.63-0.74 (m , 2 H; H-4), 1 .06-1 .35 (m , 2 H; H-6), 1 .1 (br s, 1 H; OH), 1 .67-1 .80 (m , 2 H; CH ₂ CHOH), 2.15-2.26 (m, 2 H; CH ₂ CH=CH ₂ ), 2.24-2.31 (m, 2 H; H-3), 3.93-3.98 (m, 1 H; CHOH), 5.09-5.14 (m, 1 H; CH ₂ CH=CHH), 5.17-5.23 (m , 1 H;

CH ₂ CH=CHH), 5.68-5.73 (m, 1 H; H-2), 5.91 -6.01 ppm (m, 1 H; CH ₂ CH=CH ₂ ); ³ C NMR

(125.8 MHz, C ₆ D ₆ ): 6 = -2.5 (CH ₃ ), -2.4 (CH ₃ ), 10.4 (C-4), 1 1 .1 (C-6), 22.7 (C-3), 30.6

(CH ₂ CH=CH ₂ ), 34.5 (CH ₂ CHOH), 77.6 (CHOH), 1 14.6 (CH ₂ CH=CH ₂ ), 125.2 (C-2), 139.0

(CH ₂ CH=CH ₂ ), 140.1 ppm (C-1 ); ²⁹ Si NMR (99.4 MHz, C ₆ D ₆ ): δ = -2.7 ppm; elemental analysis calcd (%) for C ₁₂ H ₂₂ OSi: C 68.51 , H 10.54; found: C 68.48, H 10.82. Odor description: herbaceous, celery, burnt, caramel.

1 ,1 , 1 -Tris(acetyloxy)-1 , 1 -dihydro-1 ,2-benziodoxol-3(1 A7)-one (Dess-Martin periodinan) (1 .61 g, 3.80 mmol) was added at 0 °C in a single portion to a stirred solution of 1 -(5,5-dimethyl-5- silacyclohex-1 -en-1 -yl)pent-4-en-1 -ol (800 mg, 3.80 mmol) in dichloromethane (60 ml), and the mixture was then allowed to warm to 20 °C within 1 h. A saturated aqueous sodium hydrogen carbonate solution (50 ml) was added, the organic phase was separated, the aqueous phase was extracted with dichloromethane (3 50 ml) and discarded, the combined organic solutions were dried over anhydrous sodium sulfate, and the solvent was removed under reduced pressure. The residue was filtered through a pad of silica gel (150 g), followed by elution with n-hexane/diethyl ether (98:2 v/v). The solvent of the filtrate (including the eluate) was removed under reduced pressure, and the residue was purified by twofold MPLC on silica gel (eluent, n-hexane/diethyl ether (99.5:0.5 v/v); flow rate, 65 ml min ^~1 ; detector wavelength, 230 nm), followed by bulb-to-bulb distillation (oven temperature 1 15 °C, 0.01 mbar) to furnish 1 -(5,5-dimethyl-5-silacyclohex-1 -en-1 - yl)pent-4-en-1 -one as a colourless liquid (410 mg, 1 .97 mmol; 52% yield). H NMR (500.1 MHz, C ₆ D ₆ ): δ = 0.04 (s, 6 H; CH ₃ ), 0.56 (5^·), 1 .72 (6 _DD ), 2.21 (6 _HH ), 6.65 (6 _X ) (AA ^' DD ^' HH ^' X system, ² J(A,A ^' ) = 12.4, ² J(D,D ^' ) = 12.4, ² J(H,H ^' ) = 15.2, ³ J(A,H) = ³ J(A ^' ,H ^' ) = 6.1 , ³ J(A,H ^' ) = ³ J(A ^' ,H) = 7.8, ³ J(H,X) = ³ J(H ^' ,X) = 5.3, ⁴ J(D,X) = ⁴ J(D ^' ,X) = 1 .4, ⁵ J(D,H) = ⁵ J(D ^' ,H ^' ) = 1 .2, ⁵ J(D,H ^' ) = ⁵ J(D ^' ,H) = 1 .8 Hz, 7 H; SiCH _A H _A CH _H H _H CH _X =CCH _D H _D ), 2.52 (6AA ), 2.59 (6 _DD ), 5.06 (6 _F ), 5.13 (6 _M ), 5.93 ppm (6 _X ) (AA ^' DD ^' FMX system, ² J(A,A ^' ) = 15.0, ² J(D,D ^' ) = 16.8, ² J(F,M) = 2.0, ³ J(A,D) = ³ J(A ^' ,D ^' ) = 6.2, ³ J(A,D ^' ) = ³ J(A,D) = 8.8, ³ J(A,X) = ³ J(A ^' ,X) = 6.6, ³ J(F,X) = 10.2, ³ J(M,X) = 17.1 , ⁴ J(A,F) = ⁴ J(A ^' ,F) = 1 .2, ⁴ J(A,M) = ⁴ J(A ^' ,M) = 1 .6 Hz, 7 H; CH _D H _D CH _A H _A CH _X =CH _F H _M ); ³ C NMR (125.8 MHz, C ₆ D ₆ ): δ = -2.7 (CH ₃ ), 9.2 (C-4), 10.8 (C-6), 23.7 (C-3), 29.2 (CH ₂ CH=CH ₂ ), 36.4 (C(0)CH ₂ ), 1 14.9 (CH ₂ CH=CH ₂ ), 138.3 (CH ₂ CH=CH ₂ ), 139.6 (C-1 ), 140.4 (C-2), 199.0 ppm (CO); ²⁹ Si NMR

(99.4 MHz, C ₆ D ₆ ): δ = -2.1 ppm; elemental analysis calcd (%) for C ₁₂ H ₂₀ OSi: C 69.17, H 9.67; found: C 69.17, H 9.79; odor description: green-fruity, galbanum, pineapple, with the typical character of 1 -(5,5-dimethylcyclohex-1 -en-1 -yl)pent-4-en-1 -one, yet without its hyacinth aspects, slightly fatty.

In an alternative synthesis of 5,5-dimethyl-5-silacyclohex-1 -ene-1 -carbaldehyde on a larger scale, a mixture of carbonylhydridotris(triphenylphosphine)rhodium(l) (180 mg, 201 μιηοΙ),

triphenylphosphine (2.50 g, 9.53 mmol), 2,6-di-ferf-butylphenol (200 mg, 969 μιηοΙ), and freshly distilled dimethyldivinylsilane (53.0 g, 472 mmol) was heated in an autoclave at 80 °C for 3 h under an atmosphere of hydrogen (40 bar) and carbon monoxide (40 bar). The reaction mixture was then allowed to cool to 20 °C. The resulting mixture (72.0 g) was then added dropwise at room temperature within 5 min to a stirred solution of morpholine (5.50 g, 63.1 mmol) and propionic acid (4.50 g, 60.7 mmol) in benzene (500 ml), and the resulting mixture was then refluxed for 1 .5 h with water being removed in a Dean-Stark trap. At room temperature, the solvent was removed under reduced pressure to afford the crude material (95 g), which was purified by bulb-to-bulb distillation (90 °C, 0.12 mbar) followed by column chromatography on silica gel (eluent, / ^' so-hexane/MTBE (98:2 v/v)) to provide 5,5-dimethyl-5-silacyclohex-1 -ene-1 -carbaldehyde as a colourless liquid (25.2 g, 163 mmol, 35% yield).

Technically, an Oppenauer oxidation is in many respects and especially on the cost side advantageous to a Dess-Martin periodinane oxidation, thus the terminal oxidation of 1 -(5,5- dimethyl-5-silacyclohex-1 -en-1 -yl)pent-4-en-1 -ol has also been carried out on this route. Thus, aluminum-tri-sec-butoxide (1 .73 g, 7.02 mmol) was added at room temperature to a solution of 1 - (5,5-dimethyl-5-silacyclohex-1 -en-1-yl)pent-4-en-1 -ol (5.00 g, 23.8 mmol) in MTBE (30 ml), followed by acetic acid (130 mg, 2.16 mmol). The resulting mixture was stirred for 5 min, prior to evacuation of the system and flushing trice with argon before freshly distilled benzaldehyde (7.60 g, 71 .6 mmol) was added over a period of 15 min at room temperature. The reaction mixture was stirred at ambient temperature for 1 h, and then poured into ice-water (50 ml). After acidifying to pH 2 by addition of aqueous hydrogen chloride, the organic phase was separated, and the aqueous one was extracted twice with MTBE. The combined organic extracts were washed in turn with water and 2N aqueous NaOH. The combined organic solutions were dried over anhydrous magnesium sulfate, and the solvent was removed under reduced pressure. The crude product was distilled to remove the excess benzaldehyde, the resulting residue was then purified by column

chromatography on silica gel (eluent, / ^' so-hexane/MTBE (98:2 v/v)), followed by bulb-to-bulb distillation (oven temperature 1 15 °C, 0.01 mbar) to furnish 1 -(5,5-dimethyl-5-silacyclohex-1 -en-1 - yl)pent-4-en-1 -one as a colourless liquid (3.40 g, 16.3 mmol, 68 % yield). Odor description: green- fruity, galbanum, pineapple, with the typical character of 1 -(5,5-dimethylcyclohex-1 -en-1 -yl)pent-4- en-1 -one, yet without its hyacinth aspects, slightly fatty.

Example 2: 1 -(5-Silaspiro[4.5]dec-7-en-7-yl)pent-4-en-1 -one (II)

A solution of 1 ,4-dibromobutane (124 g, 574 mmol) in tetrahydrofuran (150 ml) was added dropwise within 1 h to a suspension of magnesium turnings (28.0 g, 1 .15 mol) in tetrahydrofuran (100 ml), causing the reaction mixture to boil under reflux. The mixture was heated under reflux for a further 2 h, allowed to cool to 20 °C within 30 min, and then added at 0 °C within 1 h to a stirred solution of dichlorodivinylsilane (80.0 g, 523 mmol) in tetrahydrofuran (250 ml). The resulting mixture was allowed to warm to 20 °C within 20 min and stirred at this temperature for a further 2 h. Water (300 ml) was added, the organic phase was separated, the aqueous phase was extracted with diethyl ether (4 200 ml) and discarded, and the combined organic solutions were dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure, and the residue was purified by distillation in vacuo to furnish 1 ,1 -divinylsilolane as a colourless liquid (67.0 g, 485 mmol; 93% yield). B.p. 84 °C/100 mbar; H NMR (500.1 MHz, C ₆ D ₆ ): δ = 0.85 (5AA-A"A~). 1 -71 (< - _x ) (ΑΑΆ ^" Α ^{" '} ΧΧ ^' Χ ^" Χ ^{" '} system, ² J(A,A ^" ) = ² J(A ^' ,A ^{" '} ) = 14.6, ² J(X,X ^" ) = ² J(X ^' ,X ^"' ) = 1 1 .1 , ³ J(A,X) = ³ J(A ^' ,X ^' ) = 7.9, ³ J(A,X ^" ) = ³ J(A ^' ,X ^{" '} ) = 7.0, ³ J(A ^" ,X) = ³ J(A ^{" '} ,X ^' ) = 6.4, ³ J(A ^" ,X ^" ) = ³ J(A ^{" '} ,X ^"' ) = 7.7, ³ J(X,X ^' ) = 4.3, ³ J(X,X ^"' ) = ³ J(X ^' ,X ^" ) = 7.6, ³ J(X ^" ,X ^{" '} ) = 5.6, ⁴ J(A,X ^' ) = ⁴ J(A ^' ,X) = 1 .5, ⁴ J(A,X ^{" '} ) = ⁴ J(A ^' ,X ^" ) = 0.6, ⁴ J(A ^" ,X ^' ) = ⁴ J(A ^{" '} ,X) = 0.1 , ⁴ J(A ^" ,X ^"' ) = ⁴ J(A ^{" '} ,X ^" ) = 0.1 Hz, 8 H;

SiCH _A H _A CH _X H _X CH _X H _x CH _A H _A ···), 5.87 (6 _A ), 6.08 (6 _B ), 6.31 ppm (6 _C ) (ABC system, ² J(A,B) = 3.8, ³ J(A,C) = 20.3, ³ J(B,C) = 14.6 Hz, 6 H; CH _C =CH _A H _B ); ³ C NMR (125.8 MHz, C ₆ D ₆ ): δ = 1 1 .1 (C-2 and C-5), 27.6 (C-3 and C-4), 133.4 (CH=CH ₂ ), 136.2 ppm (CH=CH ₂ ); ²⁹ Si NMR (99.4 MHz, C ₆ D ₆ ): δ = 2.4 ppm; elemental analysis calcd (%) for C ₈ H ₁₄ Si: C 69.49, H 10.20; found: C 69.49, H 10.30. A mixture of 1 ,1 -divinylsilolane (8.00 g, 57.9 mmol), triphenylphosphine (760 mg, 2.90 mmol), (acetylacetonato)dicarbonylrhodium(l) (105 mg, 407 μιηοΙ), and benzene (30 ml) was heated in an autoclave at 80 °C for 7 h under an atmosphere of hydrogen (45 bar) and carbon monoxide (45 bar) and was then allowed to cool to 20 °C within 30 min. The mixture was filtered through a pad of silica gel (15 g), followed by elution with n-hexane/diethyl ether (1 :1 v/v). The solvent of the filtrate (including the eluate) was removed under reduced pressure (5 mbar), and the residue was suspended in a mixture of diethyl ether (100 ml) and water (50 ml). The organic phase was separated, the aqueous phase was extracted with diethyl ether (3 100 ml) and discarded, and the combined organic solutions were dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure (5 mbar), the residue was purified by a rapid bulb-to-bulb distillation (oven temperature 170 °C, 0.01 mbar), and the distillate was then further purified by a second bulb-to- bulb distillation (oven temperature 120 °C, 0.01 mbar) to furnish 3,3 ^' -(silolane-1 ,1 -diyl)dipropanal as a colourless liquid (1 .20 g, 6.05 mmol; 10% yield). H NMR (500.1 MHz, C ₆ D ₆ ): 6 = 0.44

(5AA-A "A ···) _> 1 -55 (δχχ χ x ) (ΑΑΆ ^" Α ^{" '} ΧΧ ^' Χ ^" Χ ^{" '} system, ² J(A,A ^" ) = ² J(A ^' ,A ^{" '} ) = 14.4, ² J(X,X ^" ) = ² J(X ^' ,X ^{" '} ) = 1 1 .3, ³ J(A,X) = ³ J(A ^' ,X ^' ) = 7.9, ³ J(A,X ^" ) = ³ J(A ^' ,X ^{" '} ) = 7.1 , ³ J(A ^" ,X) = ³ J(A ^{" '} ,X ^' ) = 6.3, ³ J(A ^" ,X ^" ) = ³ J(A ^{" '} ,X ^{" '} ) = 7.8, ³ J(X,X ^' ) = 4.5, ³ J(X,X ^{" '} ) = ³ J(X ^' ,X ^" ) = 7.4, ³ J(X ^" ,X ^{" '} ) = 5.6, ⁴ J(A,X ^' ) = ⁴ J(A ^' ,X) = 1 .5, ⁴ J(A,X ^{" '} ) = ⁴ J(A ^' ,X ^" ) = 0.6, ⁴ J(A ^" ,X ^' ) = ⁴ J(A ^{" '} ,X) = 0.1 , ⁴ J(A ^" ,X ^{" '} ) = ⁴ J(A ^{" '} ,X ^" ) = 0.1 Hz, 8 H; SiCH _A H _A CH _X H _X CH _X H _x CH _A H _A ···), 0.59 (6^ ), 1 .89 (6 _DD ), 9.43 ppm (6 _X )

(AA ^' DD ^' X system, ² J(A,A ^' ) = 15.4, ² J(D,D ^' ) = 12.6, ³ J(A,D) = ³ J(A ^' ,D ^' ) = 5.5, ³ J(A,D ^' ) = ³ J(A ^' ,D) = 10.8, ³ J(D,X) = ³ J(D ^' ,X) = 1 .4 Hz, 10 H; CH _A H _A CH _D H _D CH _X ); ³ C NMR (125.8 MHz, C ₆ D ₆ ): δ = 5.0 (CH ₂ CH ₂ CH), 10.1 (C-2 and C-5), 27.5 (C-3 and C-4), 38.4 (CH ₂ CH), 200.6 ppm (CHO); ²⁹ Si NMR (99.4 MHz, C ₆ D ₆ ): δ = 21 .8 ppm; elemental analysis calcd (%) for C ₁₀ H ₁₈ O ₂ Si: C 60.56, H 9.15; found: C 60.49, H 9.36.

A mixture of 1 ,1 -divinylsilolane (13.6 g, 98.3 mmol), triphenylphosphine (1 .29 g, 4.92 mmol), (acetylacetonato)dicarbonylrhodium(l) (178 mg, 690 μιηοΙ), and benzene (50 ml) was heated in an autoclave at 80 °C for 7 h under an atmosphere of hydrogen (45 bar) and carbon monoxide (45 bar), and was then allowed to cool to 20 °C within 30 min. The resulting mixture (containing intermediate 3,3'-(silolane-1 ,1 -diyl)dipropanal as intermediate) was then added dropwise at 0 °C within 1 h to a stirred 0.5 M solution of hydrogen chloride in diethyl ether (300 ml, 150 mmol of HCI), and the resulting mixture was then kept undisturbed at 20 °C for 18 h. The mixture was filtered through a pad of silica gel (180 g), followed by elution with n-hexane/diethyl ether (1 :1 v/v). The solvent of the filtrate (including the eluate) was removed under reduced pressure, and the residue was purified by flash chromatography on silica gel (eluent, n-hexane/diethyl ether (7:3 v/v)), followed by bulb-to-bulb distillation (oven temperature 1 10 °C, 0.02 mbar) to furnish

5-silaspiro[4.5]dec-7-ene-7-carbaldehyde as a colourless liquid (5.88 g, 32.6 mmol; 33% yield). H NMR (500.1 MHz, C ₆ D ₆ ): δ = 0.54 (6^ ), 0.55 (δ _ΒΒ ), 1 .59 (δ _χχ ), 1 .60 (δ _γγ ) (ΑΑ ^' ΒΒ ^' ΧΧΎΥ ^' system, ² J(A,B) = ² J(A ^' ,B ^' ) = 10.3, ² J(X,Y) = ² J(X ^' ,Y ^' ) = 13.2, ³ J(A,X) = ³ J(A ^' ,X ^' ) = 7.7, ³ J(A,Y) = ³ J(A ^' ,Y ^' ) = 6.7, ³ J(B,X) = ³ J(B ^' ,X ^' ) = 7.0, ³ J(B,Y) = ³ J(B ^' ,Y ^' ) = 7.8, ³ J(X,X ^' ) = 5.1 , ³ J(X,Y ^' ) = ³ J(X ^' ,Y) = 7.8, ³ J(Y,Y ^' ) = 4.8, ⁴ J(A,X ^' ) = ⁴ J(A ^' ,X) = 0.2, ⁴ J(A,Y ^' ) = ⁴ J(A ^' ,Y) = 0.03, ⁴ J(B,X ^' ) = ⁴ J(B ^' ,X) = 0.01 , ⁴ J(B,Y ^' ) = ⁴ J(B ^' ,Y) = 0.4 Hz, 8 H; S\CH _A H _B CH _x H _Y CH _x H _r CH _A H _B ), 0.60 (5^·). ⁶⁴ (¾ _D ) _> ^{2 9} (6 _HH ), 6.21 (δχ) (AA ^' DD ^' HH ^' X system, ² J(A,A ^' ) = 12.4, ² J(D,D ^' ) = 12.4, ² J(H,H ^' ) = 15.2, ³ J(A,H) = ³ J(A ^' ,H ^' ) = 6.3, ³ J(A,H ^' ) = ³ J(A ^' ,H) = 7.5, ³ J(H,X) = ³ J(H ^' ,X) = 4.9, ⁴ J(D,X) = ⁴ J(D ^' ,X) = 1 .5, ⁵ J(D,H) = ⁵ J(D ^' ,H ^' ) = 2.0, ⁵ J(D,H ^' ) = ⁵ J(D ^' ,H) = 1 .3 Hz, 7 H; SiCH _A H _A CH _H H _H CH _X =CCH _D H _D ), 9.42 ppm (s, 1 H; CHO); ³ C NMR (125.8 MHz, C ₆ D ₆ ): δ = 7.2 (C-6), 8.0 (C-10), 1 1 .1 (C-1 and C-4), 24.5 (C-9),

27.2 (C-2 and C-3), 141 .4 (C-7), 152.5 (C-8), 193.8 ppm (CHO); ²⁹ Si NMR (99.4 MHz, C ₆ D ₆ ):

6 = 13.9 ppm; elemental analysis calcd (%) for C ₁₀ H ₁₆ OSi: C 66.61 , H 8.94; found: C 66.38, H 9.02.

4-Bromo-1 -butene (15.4 g, 1 14 mmol) was added dropwise within 30 min to a suspension of magnesium turnings (3.70 g, 152 mmol) in diethyl ether (150 ml), causing the reaction mixture to boil under reflux. The mixture was heated under reflux for a further h, allowed to cool to 20 °C within 20 min, and then added at -10 °C within 30 min to a stirred solution of 5-silaspiro[4.5]dec-7- ene-7-carbaldehyde (13.7 g, 76.0 mmol) in diethyl ether (250 ml). The resulting mixture was allowed to warm to 20 °C within 30 min and was then stirred at this temperature for a further h, a saturated aqueous solution of ammonium chloride (200 ml) was added, the organic phase was separated, the aqueous phase was extracted with diethyl ether (3 ^χ 100 ml) and discarded, and the combined organic solutions were dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure, and the residue was purified by flash chromatography on silica gel (eluent, n-hexane/diethyl ether (7:3 v/v)), followed by bulb-to-bulb distillation (oven temperature 170 °C, 0.02 mbar) to furnish 1 -(5-silaspiro[4.5]dec-7-en-7-yl)pent-4-en-1 -ol as a colourless liquid (15.5 g, 65.6 mmol; 86% yield). H NMR (500.1 MHz, C ₆ D ₆ ): δ = 0.63-0.74 (m, 4 H; H-1 and H-4), 0.75- 0.83 (m, 2 H; H-10), 1 .19-1 .47 (m, 2 H; H-6), 1 .64-1 .82 (m, 7 H; H-2, H-3, OH, and CH ₂ CHOH), 2.13-2.33 (m, 4 H; H-9 and CH ₂ CH=CH ₂ ), 3.95^.00 (m, 1 H; CHOH), 5.08-5.13 (m, 1 H;

CH ₂ CH=CHH), 5.16-5.22 (m, 1 H; CH ₂ CH=CHH), 5.72-5.76 (m, 1 H; H-8), 5.90-6.00 ppm (m, 1 H; CH ₂ CH=CH ₂ ); ³ C NMR (125.8 MHz, C ₆ D ₆ ): δ = 9.2 (C-10), 9.8 (C-6), 1 1 .6 (C-1 or C-4), 1 1 .7 (C-1 or C-4), 23.0 (C-9), 27.4 (C-2 or C-3), 27.5 (C-2 or C-3), 30.6 (CH ₂ CHOH), 34.5 (CH ₂ CH=CH ₂ ), 77.5 (CHOH), 1 14.7 (CH ₂ CH=CH ₂ ), 125.6 (C-8), 139.0 (CH ₂ CH=CH ₂ ), 140.4 ppm (C-7); ²⁹ Si NMR (99.4 MHz, C ₆ D ₆ ): δ = 14.9 ppm; elemental analysis calcd (%) for C ₁₄ H ₂₄ OSi: C 71 .12, H 10.23; found: C 71 .29, H 10.40.

1 ,1 ,1 -Tris(acetyloxy)-1 ,1 -dihydro-1 ,2-benziodoxol-3(1 A7)-one (Dess-Martin periodinan) (17.1 g,

40.3 mmol) was added at 0 °C in a single portion to a stirred solution of 1 -(5-silaspiro[4.5]dec-7-en- 7-yl)pent-4-en-1 -ol (9.56 g, 40.4 mmol) in dichloromethane (400 ml), and the mixture was then allowed to warm to 20 °C within 1 h. A saturated aqueous sodium hydrogen carbonate solution (150 ml) was added, the organic phase was separated, the aqueous phase was extracted with dichloromethane (3 ^χ 100 ml) and discarded, the combined organic solutions were dried over anhydrous sodium sulfate, and the solvent was removed under reduced pressure. The resulting residue was filtered through a pad of silica gel (200 g), followed by elution with n-hexane/diethyl ether (95:5 v/v). The solvent of the filtrate (including the eluate) was removed under reduced pressure, and the resulting residue was purified by flash chromatography on silica gel (eluent, n- hexane/di ethyl ether (98:2 v/v)), followed by MPLC on silica gel (eluent, n-hexane/acetone

(99.8:0.2 v/v); flow rate, 50 ml min ^~1 ; detector wavelength, 230 nm) and then by bulb-to-bulb distillation (oven temperature 135 °C, 0.01 mbar) to furnish 1 -(5-silaspiro[4.5]dec-7-en-7-yl)pent-4- en-1 -one as a colourless liquid (4.30 g, 18.3 mmol; purity 99.5%; 45% yield). H NMR (500.1 MHz, C ₆ D ₆ ): δ = 0.60 (5^·), 0.63 (δ _ΒΒ ·), 1 .62 (δ _χχ ·), 1 .65 (δ _γγ ·) (ΑΑ ^' ΒΒ ^' ΧΧΎΥ ^' system, ² J(A,B) = ² J(A ^' ,B ^' ) = 14.8, ² J(X,Y) = ² J(X ^' ,Y ^' ) = 12.9, ³ J(A,X) = ³ J(A ^' ,X ^' ) = 7.6, ³ J(A,Y) = ³ J(A ^' ,Y ^' ) = 7.1 , ³ J(B,X) = ³ J(B ^' ,X ^' ) = 7.1 , ³ J(B,Y) = ³ J(B ^' ,Y ^' ) = 7.6, ³ J(X,X ^' ) = 4.9, ³ J(X,Y ^' ) = ³ J(X ^' ,Y) = 7.7, ³ J(Y,Y ^' ) = 5.0, ⁴ J(A,X ^' ) = ⁴ J(A ^' ,X) = 0.7, ⁴ J(A,Y ^' ) = ⁴ J(A ^' ,Y) = 0.3, ⁴ J(B,X ^' ) = ⁴ J(B ^' ,X) = 0.4, ⁴ J(B,Y ^' ) = ⁴ J(B ^' ,Y) = 0.7 Hz, 8 H; S\CH _A H _B CH _X H _Y CH _X H _Y CH _A H _B ), 0.67 (6AA ), 1 .82 (6 _DD ), 2.23 (δ _ΗΗ ), 6.65 (δ _χ )

(AA ^' DD ^' HH ^' X system, ² J(A,A ^' ) = 1 1 .0, ² J(D,D ^' ) = 9.4, ² J(H,H ^' ) = 13.6, ³ J(A,H) = ³ J(A ^' ,H ^' ) = 6.0, ³ J(A,H ^' ) = ³ J(A ^' ,H) = 7.8, ³ J(H,X) = ³ J(H ^' ,X) = 5.3, ⁴ J(D,X) = ⁴ J(D ^' ,X) = 1 .4, ⁵ J(D,H) = ⁵ J(D ^' ,H ^' ) = 2.1 , ⁵ J(D,H ^' ) = ⁵ J(D ^' ,H) = 0.8 Hz, 7 H; SiCH _A H _A CH _H H _H CH _X =CCH _D H _D ), 2.51 (6AA ), 2.58 (6 _DD ), 5.06 (6 _F ), 5.13 (δ _Μ ), 5.93 ppm (δ _χ ) (AA ^' DD ^' FMX system, ² J(A,A ^' ) = 15.0, ² J(D,D ^' ) = 16.8, ² J(F,M) = 2.0, ³ J(A,D) = ³ J(A ^' ,D ^' ) = 6.2, ³ J(A,D ^' ) = ³ J(A ^' ,D) = 8.7, ³ J(A,X) = ³ J(A ^' ,X) = 6.6, ³ J(F,X) = 10.2, ³ J(M,X) = 17.1 , ⁴ J(A,F) = ⁴ J(A ^' ,F) = 1 .2, ⁴ J(A,M) = ⁴ J(A ^' ,M) = 1 .6 Hz, 7 H; CH _D H _D CH _A H _A CH _X =CH _F H _M ); 3C NMR (125.8 MHz, C ₆ D ₆ ): δ = 8.0 (C-10), 9.5 (C-6), 1 1 .4 (C-1 and C-4), 23.9 (C-9), 27.3 (C-2 and C-3), 29.2 (CH ₂ CH=CH ₂ ), 36.4 (C(0)CH ₂ ), 1 14.9 (CH ₂ CH=CH ₂ ), 138.3 (CH ₂ CH=CH ₂ ), 139.7 (C-7), 140.7 (C-8), 198.9 ppm (CO); ²⁹ Si NMR (99.4 MHz, C ₆ D ₆ ): 6 = 15.3 ppm; elemental analysis calcd (%) for C ₁₄ H ₂₂ OSi: C 71 .73, H 9.46; found: C 71 .47, H 9.42; odor description: green-fruity, galbanum and pineapple odor with metallic facets, close to 1 -(5,5-dimethylcyclohex-1 -en-1 -yl)pent- 4-en-1 -one, yet without its hyacinth aspects.

1 -(5-Silaspiro[4.5]dec-7-en-7-yl)pent-4-en-1 -one was further purified via its (2,4-dinitrophenyl)- hydrazine, to which purpose sulphuric acid (1 1 ml), water (17 ml), and ethanol (45 ml) were added sequentially at 20 °C in single portions to (2,4-dinitrophenyl)hydrazine (5.58 g of a 50% suspension of (2,4-dinitrophenyl)hydrazine in water; 14.1 mmol of (2,4-dinitrophenyl)hydrazine), followed by dropwise addition of a solution of 1 -(5-silaspiro[4.5]dec-7-en-7-yl)pent-4-en-1 -one (3.00 g, 12.8 mmol; purity 99.5%) in ethanol (55 ml) at this temperature within 45 min. The resulting precipitate was separated by suction filtration and washed with water (5 25 ml) to furnish a red solid, which was dried in vacuo (20 °C, 0.02 mbar, 2 h) and then recrystallized from methanol (750 ml; slow cooling of a boiling solution to 20 °C and crystallization over a period of 1 d). The precipitate was isolated by suction filtration, washed with methanol (-20 °C, 25 ml), and dried in vacuo (20 °C, 0.02 mbar, 4 h) to furnish a red crystalline solid, which was again recrystallized from methanol until HPLC analysis indicated no further impurities. The resulting 1 -(5-silaspiro[4.5]dec-7- en-7-yl)pent-4-en-1 -one (2,4-dinitrophenyl)hydrazone was then isolated as a red crystalline solid (2.90 g, 7.00 mmol; 55% yield). M.p. 135 °C; H NMR (500.1 MHz, C ₆ D ₆ ): δ = 0.74 (6^ ), 0.79 (δ _ΒΒ ), 1 .73 (δ _χχ ), 1 .79 (δ _γγ ) (ΑΑ ^' ΒΒ ^' ΧΧΎΥ ^' system, ² J(A,B) = ² J(A ^' ,B ^' ) = 14.9, ² J(X,Y) = ² J(X ^' ,Y ^' ) = 12.9, ³ J(A,X) = ³ J(A ^' ,X ^' ) = 7.4, ³ J(A,Y) = ³ J(A ^' ,Y ^' ) = 7.1 , ³ J(B,X) = ³ J(B ^' ,X ^' ) = 7.2, ³ J(B,Y) = ³ J(B ^' ,Y ^' ) = 7.5, ³ J(X,X ^' ) = 4.9, ³ J(X,Y ^' ) = ³ J(X ^' ,Y) = 7.6, ³ J(Y,Y ^' ) = 4.8, ⁴ J(A,X ^' ) = ⁴ J(A ^' ,X) = 0.8, ⁴ J(A,Y ^' ) = ⁴ J(A ^' ,Y) = 0.4, ⁴ J(B,X ^' ) = ⁴ J(B ^' ,X) = 0.5, ⁴ J(B,Y ^' ) = ⁴ J(B ^' ,Y) = 0.8 Hz, 8 H; S\CH _A H _B CH _X H _Y CH _X H _Y CH _A H _B ), 0.81 {δ^), 2.06 (6 _DD ), 2.37 (δ _ΗΗ ), 6.26 (δ _χ ) (AA ^' DD ^' HH ^' X system, ² J(A,A ^' ) = 1 1 .0, ² J(D,D ^' ) = 8.5, ² J(H,H ^' ) = 13.2, ³ J(A,H) = ³ J(A ^' ,H ^' ) = 5.9, ³ J(A,H ^' ) = ³ J(A ^' ,H) = 7.9, ³ J(H,X) = ³ J(H ^' ,X) = 5.6, ⁴ J(D,X) = ⁴ J(D ^' ,X) = 1 .0, ⁵ J(D,H) = ⁵ J(D ^' ,H ^' ) = 0.6, ⁵ J(D,H ^' ) = ⁵ J(D ^' ,H) = 1 .6 Hz, 7 H; SiCH _A H _A CH _H H _H CH _X =CCH _D H _D ), 2.19 {δ _Μ ^■ ), 2.44 (6 _DD ), 5.12 (6 _F ), 5.21 (6 _M ), 5.86 (δχ) (AA ^' DD ^' FMX system, ² J(A,A ^' ) = 13.1 , ² J(D,D ^' ) = 13.0, ² J(F,M) = 1 .5, ³ J(A,D) = ³ J(A ^' ,D ^' ) = 6.1 , ³ J(A,D ^' ) = ³ J(A ^' ,D) = 10.3, ³ J(A,X) = ³ J(A ^' ,X) = 6.8, ³ J(F,X) = 10.1 , ³ J(M,X) = 17.0, ⁴ J(A,F) = ⁴ J(A ^' ,F) = 1 .1 , ⁴ J(A,M) = ⁴ J(A ^' ,M) = 1 .5 Hz, 7 H; CH _D H _D CH _A H _A CH _X =CH _F H _M ), 7.70 (6 _A ), 7.84 (6 _D ), 8.95 (6 _M ), 11 .2 ppm (6 _X ) (ADMX system, ³ J(A,D) = 9.5, ⁴ J(D,M) = 2.6, ⁵ J(D,X) = 0.7 Hz, 4 H;

C ₆ H ₃ (N0 ₂ ) ₂ NH _x (H-3 _M , H-5 _D , H-6 _A )); ³ C NMR (125.8 MHz, C ₆ D ₆ ): δ = 8.6 (C-10, 5- silaspiro[4.5]dec-7-en-7-yl (= 5-sila)), 1 1 .3 (C-6, 5-sila), 1 1 .6 (C-1 and C-4, 5-sila), 24.1 (C-9, 5-sila), 25.7 (C(N)CH ₂ ), 27.4 (C-2 and C-3, 5-sila), 30.5 (CH ₂ CH=CH ₂ ), 1 16.0 (C-6, C ₆ H ₃ (N0 ₂ ) ₂ ), 1 16.7 (CH ₂ CH=CH ₂ ), 123.4 (C-3, C ₆ H ₃ (N0 ₂ ) ₂ ), 129.57 (C-5, C ₆ H ₃ (N0 ₂ ) ₂ ), 129.62 (C-2, C ₆ H ₃ (N0 ₂ ) ₂ ), 134.5 (C-8, 5-sila), 136.1 (CH ₂ CH=CH ₂ ), 136.8 (C-7, 5-sila), 138.1 (C-4, C ₆ H ₃ (N0 ₂ ) ₂ ), 144.8 (C-1 , C ₆ H ₃ (N0 ₂ ) ₂ ), 157.2 ppm (C(N)CH ₂ ); ⁵ N NMR (50.7 MHz, C ₆ D ₆ ): δ = -234.3 (C ₆ H ₃ (N0 ₂ ) ₂ A/HN), - 77.2 (C ₆ H ₃ (N0 ₂ ) ₂ NHA/), -15.5 (A/0 ₂ ), -13.2 ppm (A/0 ₂ ); ²⁹ Si NMR (99.4 MHz, C ₆ D ₆ ): 6 = 15.8 ppm; elemental analysis calcd (%) for C ₂₀ H ₂₆ N ₄ O ₄ Si: C 57.95, H 6.32, N 13.52; found: C 58.08, H 6.24, N 13.74.

The thus obtained 1 -(5-silaspiro[4.5]dec-7-en-7-yl)pent-4-en-1 -one (2,4-dinitrophenyl)hydrazone was then hydrolyzed by heating a mixture of this hydrazone (1 .10 g, 2.65 mmol), p-toluenesulfonic acid monohydrate (46 mg, 242 μιηοΙ), and acetone (50 ml) in a sealed tube at 60 °C for 65 h.The resulting mixture was allowed to cool to 20 °C within 1 h, and filtered through a pad of silica gel (30 g), followed by elution with n-hexane/diethyl ether (95:5 v/v). The solvent of the filtrate

(including the eluate) was removed under reduced pressure, and the residue was purified by flash chromatography on silica gel (eluent, n-hexane/diethyl ether (98:2 v/v)), followed by bulb-to-bulb distillation (oven temperature 135 °C, 0.01 mbar) to furnish extremely pure 1 -(5-silaspiro[4.5]dec-7- en-7-yl)pent-4-en-1 -one as a colourless liquid (450 mg, 1 .92 mmol; 72% yield), odor description: green-fruity, galbanum and pineapple odor with metallic facets, close to 1 -(5,5-dimethylcyclohex-1 - en-1 -yl)pent-4-en-1 -one, yet without its hyacinth aspects.

Example 3: Feminine rose accord employing 1 -(5,5-dimethyl-5-silacyclohex-1 -en-1 -yl)pent-4- en-1 -one (Example 1) for use in cosmetic products and toiletries

COMPOUND/INGREDIENT PARTS PER WEIGHT 1/1000

1 . (3Z)-HEX-3-ENYL ACETATE 7 2. (3Z)-HEX-3-ENYL PROPIONATE 10%/DPG 25 3. CITRONELLOL 45 4. β-DAMASCONE 10%/DPG 35

5. DIPROPYLENE GLYCOL (DPG) 102

6. ETHYL DECADIENOATE 7

7. ETHYL VANILLIN 10%/DPG 1

8. EUGENOL 5

9. GERANIUM OIL, EGYPT 10

10. GERANYL PHENYLACETATE 10

1 1 . HEDIONE (METHYL 2-(3'-OXO-2'-PENTYLCYCLOPENTYL)ACETATE) 250

12. a-HEXYL CINNAMIC ALDEHYDE 25

13. INDOLE 1 %/DPG 45

14. NIRVANOLIDE™ ((10Z)-13-METHYLOXACYCLOPENTADEC-10-EN-2-ONE) 10

15. PECHE PURE (Y-UNDECALACTONE) 10%/DPG 7

16. PEPPERWOOD™ (3J-DIMETHYLOCTA-1 .6-DIEN-3-YL

DIMETHYLCARBAMATE) 200

17. PETALIA™ (CYCLOHEXYLIDENE-O-TOLYLACETONITRILE) 30

18. 2-PHENYLETHANOL 100

19. 2-PHENYLETHYL ACETATE 15

20. 2-PHENYLETHYL CINNAMATE 25

21 . 2-PHENYLETHYL SALICYLATE, CRYSTALLINE 25

22. ROSE ABSOLUTE 1

23. SERENOLIDE™ (2-(1 '-(3",3"-DIMETHYLCYCLOHEXYL)ETHOXY)- 2-METHYLPROPYL CYCLOPROPANECARBOXYLATE) 8

24. TOSCANOL™ (1 -CYCLOPROPYLMETHYL-4-METHOXYBENZENE) 10%/DPG 4

25. 1 -(5,5-DIMETHYL-5-SILACYCLOHEX-1 -EN-1 -YL)PENT-4-EN-1 -ONE 8

TOTAL 1000

At only 0.8%, 1 -(5,5-dimethyl-5-silacyclohex-1 -en-1 -yl)pent-4-en-1 -one (Example 1 ) opened up this rose fragrance in conveying naturalness and freshness in a green direction, introducing aspects of the rose stem and the leaves of the rose. Thereby this compound boosts the volume of the fragrance and brightened up the overall floral nature. Extending the metallic aspects of this rose theme, it increased also its bloom, amplified the radiance of the whole composition, and provided a distinct and most characteristic signature to this modern rose perfume composition. Example 4: Refreshing fruity, marine-aquatic unisex perfume employing 1 -(5,5-dimethyl-5- silacyclohex-1 -en-1 -yl)pent-4-en-1 -one (Example 1 )

COMPOUND/INGREDIENT PARTS PER WEIGHT 1/900

1 . ANISYL ACETAE 25

2. CALONE 1951™ (7-METHYL-2H-BENZO[b][1 ,4]DIOXEPIN-3(4H)-ONE) 7

3. CALYPSONE™ (6-METHOXY-2,6-DIMETHYLOCTANAL) 20

4. CEPIONATE™ (METHYL 2-(3-OXO-2-PENTYLCYCLOPENTYL)ACETATE) 150

5. CITRONELLOL 45

6. CYCLOGALBANATE™ (ALLYL 2-(CYCLOHEXYLOXY)ACETATE) 2

7. Y-DECALACTONE 10%/DPG 25

8. DIPROPYLENE GLYCOL (DPG) 131

9. FLORYMOSS™ (1 -(CYCLOOCT-3-EN-1 -YL)PROPAN-1 -OL) 45

10. GEORGYWOOD™ (2-ACETYL-1 ,2,3,4,5,6,7,8-OCTAHYDRO-1 ,2,8,8- TETRAMETHYLNAPHTHALENE) 120

1 1 . INDOLENE (8,8-DI(1 H-INDOL-3-YL)-2,6-DIMETHYLOCTAN-2-OL) 50%

/CASTOR OIL 1 %/DPG 8

12. β-ΙΟΝΟΝΕ 25

13. LILIAL™ (2-METHYL-3-(4-TERT-BUTYLPHENYL)PROPANAL) 80

14. LINALOOL, SYNTHETIC 25

15. MELONAL™ (2,6-DIMETHYLHEPT-5-ENAL) 10%/DPG 5

16. 2-(2-MERCAPTOPROPAN-2-YL)-5-METHYLCYCLOHEXANONE 0.1 %

/TEC 10%/DPG 12

17. ROSE ABSOLUTE, MOLECULARLY DESTILLED 2

18. SERENOLIDE™ (2-(1 '-(3",3"-DIMETHYLCYCLOHEXYL)ETHOXY)- 2-METHYLPROPYL CYCLOPROPANECARBOXYLATE) 90

19. THIBETOLIDE™ (OXACYCLOHEXADECAN-2-ONE) 40

20. TROPIONAL™ (3-(BENZO[D][1 ,3]DIOXOL-5-YL)-2-METHYLPROPANAL) 35

21. 1 -(5,5-DIMETHYL-5-SILACYCLOHEX-1 -EN-1 -YL)PENT-4-EN-1 -ONE 8

TOTAL 900

At less than 0.9%, 1 -(5,5-dimethyl-5-silacyclohex-1 -en-1 -yl)pent-4-en-1 -one (Example 1 ) combined very well with the fruity-green Cylogalbanate to provide a transparent green pineapple note that provided radiance, depth and crispness. The 1 -(5,5-dimethyl-5-silacyclohex-1 -en-1 -yl)pent-4-en-1 - one not only provided a fruity character but also increases considerably the overall floral character of the composition, while preserving its freshness and transparency. While the dry-down of the fragrance became less musky, it actually gained a fresh-fruity twist due to the high substantivity and low volatility of the 1 -(5,5-dimethyl-5-silacyclohex-1 -en-1 -yl)pent-4-en-1 -one. Thereby, the compound provided a distinct green-fruity signature on the composition from the top to the basenote.

Example 5: Dark woody masculine gourmand fine fragrance employing 1 -(5- silaspiro[4.5]dec-7-en-7-yl)pent-4-en-1 -one (II) (Example 2)

COMPOUND/INGREDIENT PARTS PER WEIGHT 1/900

1 . ACETYL ISOEUGENOL, CRYSTALLINE 8

2. ALLYL AMYL GLYCOLATE (ALLYL 2-(ISOPENTYLOXY)ACETATE) 35

3. AMBRINOL™ ((2,5,5-TRIMETHYL-1 ,2, 3,4,4a, 5,6, 7-OCTAHYDRO- NAPHTHALEN-2-OL)) 10%/DPG 8

4. CLARITONE™ (2,4,4, 7-TETRAMETHYL-6-OCTEN-3-ONE) 25

5. Y-DECALACTONE 10%/DPG 25

6. DIHYDROMYRCENOL 45

7. DIPROPYLENE GLYCOL (DPG) 27

8. ETHYL MALTOL 5

9. FLORHYDRAL™ (3-(3-ISOPROPYLPHENYL)BUTANAL) 7

10. GARDENOL™ (1 -PHENYLETHYL ACETATE) 15

1 1 . (3Z)-HEXEN-3-YL ISOBUTYRATE 10%/DPG 8

12. KARMAFLOR™ ((4Z)-HEPT-4-EN-2-YL SALICYLATE) 100

13. LEMON OIL, ITALY 70

14. NIMBEROL™ (1 -(2,2,6-TRIMETHYLCYCLOHEXYL)HEXAN-3-OL) 25

15. NIRVANOLIDE™ ((10Z)-13-METHYLOXACYCLOPENTADEC-10-EN-2-ONE) 45

16. NUTMEG OIL, INDONESIA 25

17. PASHM INOL™ (1 -METHYL-2-[(2,2,3-TRIMETHYLCYCLOPENTYL)METHYL]- CYCLOPROPANEMETHANOL) 55

18. PATCHOULI OIL, INDONESIA 75

19. PETALIA™ (CYCLOHEXYLIDENE-O-TOLYLACETONITRILE) 45

20. 2-PHENYLETHANOL 2

21 . SCLARENE (4,5,6,7,8,9,10,1 1 ,12, 13-DECAHYDROCYCLODO- DECA[d]OXAZOLE) 50%/TEC 50

22. SERENOLIDE™ (2-(1 '-(3",3"-DIMETHYLCYCLOHEXYL)ETHOXY)- 2-METHYLPROPYL CYCLOPROPANECARBOXYLATE) 45

23. SPIRAMBRENE™ (2 ^, ,2 ^, ,3,7,7-PENTAMETHYLSPIRO[BICYCLO[4.1 .0]- HEPTANE-2,5'-[1 ,3]DIOXANE]) 15

STEMONE (5-METHYLHEPTAN-3-ONE OXIME) 10%/DPG 5

25. TETRAHYDROLINALYL ACETATE 55

26. 1 -(5-SILASPIRO[4.5]DEC-7-EN-7-YL)PENT-4-EN-1 -ONE (II) 80

TOTAL 900

At a rather high dose level of 8.89% 1 -(5-silaspiro[4.5]dec-7-en-7-yl)pent-4-en-1 -one conveyed an interesting fruity metallic effect on the intense dark woody-ambery accord around Nimberol™, patchouli oil, Sclarene™ and Spirambrene™. This created an interesting vibrancy in the fond of this masculine gourmand theme, leading to a rich contrast with the sweet cotton-candy aspects of the rather highly dosed ethyl maltol. As a result, this new sila-compound thus provided lift and depth to the composition, and a cool metallic fruityness that wais juxtaposed to the sweet, warm and dark woody-ambery elements of the theme. This allowed a rather sweet gourmand theme to be employed in a masculine context, but at the same time prevented the composition from turning too dark and impervious woody-ambery. The low volatility and high substantivity of this silaspirocyclic compound was key to this interesting effect on such fond ingredients as ethyl maltol and tenacious woody ambers, which allowed for a new and uncommon signature upon dry-down.