Technical field The present invention relates to the field of perfumery. More particularly, it concerns the use as perfuming ingredient of a lower alkyl ester of 4,6,6-trimethyl-l,3- cyclohexadiene- 1 -carboxylate or 4,6,6-trimethyl-3-cyclohexene- 1 -carboxylate. The present invention concerns also the compositions or articles associated with said compound.

Prior art The methyl and ethyl esters of the invention are all known as such. Ethyl 4,6,6- trimethyl-1, 3 -cyclohexadiene-1 -carboxylate has been reported by I.Alkonyi et al. in Acta Chimica Academiae Scientiarium Hungaricae 1957, JL2, 289 and is described as chemical intermediate. The methyl analogue has been similarly described by K.-F. Chen et a.l in J.Chem.Soc. Perkin Trans. I, 1996, 1213. The methyl or ethyl esters of 4,6,6-trimethyl-3- cyclohexene-1-carboxylic acid have been disclosed as intermediate in J. Org.Chem., 1969, 34, 2196. However, none of said documents discloses or suggests the organoleptic properties of the compounds of formula (I), or their use in the field of perfumery. The patent application EP 955290 Al discloses perfuming ingredients having a general formula including the invention's compounds. However, in said patent application, the compounds of the present invention are not specifically disclosed, do not belong to preferred class of compounds and there is no mention or suggestion of the particular and unique odor notes that can be conferred by the present invention's esters. Now, in perfumery, there is a recognized need for compounds capable of imparting odor notes of the type saffron and spicy so as to complete the needs .of perfumers. The use of the compounds of formula (I) fulfills the above-mentioned need.

-Desmption-of-the-invention We have now surprisingly found that a compound of formula wherein the dotted line represents ,a single or double bond and R represents a linear or branched C1-C4 alkyl group; can advantageously be used as perfuming ingredient to impart spicy/saffron-like odor notes to the composition in which it is added. The compounds of formula (I) wherein R is a methyl or ethyl group represent particular embodiments of the invention, and in particular those wherein the dotted line represents a double bond. Amongst the invention's compound, one may cite ethyl 4,6,6-trimethyl-l,3- cyclohexadiene-1-carboxylate which has an odor characterized by a dominant spicy- saffron note and charcter which is particularly warm and pleasant. The spicy character of this compound has also a slight balsamic-myrrh aspect. Furthermore, the bottom notes of said compound possesses also a cypriol-like nuance. Another invention's compound is methyl 4,6,6-trimethyl-l,3-cyclohexadiene-l- carboxylate which has an odor similar to that of the ethyl ester mentioned above, but distinguishes itself by a slightly less powerful odor. Furthermore one may also cite the methyl or ethyl 4,6,6-trimethyl-3-cyclohexene- 1-carboxylate. Also these two esters are characterized by a well perceivable saffron note, however the cypriol-like connotation of the above-mentioned ester is here replaced by a rosy-like aspect. To the contrary of the prior art compounds cited in the above-mentioned EP application, the invention's compounds are characterized by odor properties which lack of, or do not possess significant, floral notes, and all the less character. Furthermore, the odor of the invention's compounds differs also from the one of the prior art ingredients by not imparting a woody character to the compositionjn which it is added. Said differences lend to the invention's compounds and the prior art compounds to be each suitable for different uses, i.e. to impart different organoleptic impressions. The ethyl 4,6,6-trimethyl-l,3-cyclohexadiene-l-carboxylate is a particularly preferred embodiment of the invention due to its superior and cleaner saffron note. As mentioned above, the invention concerns the use of a compound of formula (I) as perfuming ingredients. In other words it concerns a method to confer, enhance, improve or modify the odor properties of a perfuming composition or of a perfumed article, which method comprises adding to said composition or article an effective amount of at least a compound of formula (I). By "use of a compound of formula (I)" it has to be understood here also the use of any composition containing compound (I) and which can be advantageously employed in perfumery industry as active ingredients. Said compositions, which are in fact perfuming compositions that can be advantageously employed as perfuming ingredient, are also an object of the present invention. Therefore, another object of the present invention is a perfuming composition comprising: i) as perfuming ingredient, at least one invention's compound as defined above; ii) at least one ingredient selected from the group consisting of a perfumery carrier and a perfumery base; and iii) optionally at least one perfumery adjuvant. By "perfumery carrier" we mean here a material which is practically neutral from a perfumery point of view, i.e. that does not significantly alter the organoleptic properties of perfuming ingredients. Said carrier may be a liquid or a solid. As liquid carrier one may cite, as non-limiting examples, an emulsifying system, i.e. a solvent and a surfactant system, or a solvent commonly used in perfumery. A detailed description of the nature and type of solvents commonly used in perfumery cannot be exhaustive. However, one can cite as non-limiting examples solvents such as dipropyleneglycol, diethyl phthalate, isopropyl myristate, benzyl benzoate, 2-(2- ethoxyethoxy)-l-ethanol or ethyl citrate, which are the most commonly used. As solid carrier one may cite, as non-limiting examples, absorbing gums or -polymers, - or yet encapsulating materials. Examples of such materials, for example, may comprise wall-forming and plasticizing materials, such as mono, di- or trisaccharides, natural or modified starches, hydrocolloids, cellulose derivatives, polyvinyl acetates, polyvinylalcohols, proteins or pectins, or yet the materials cited in reference texts such as H. Scherz, Hydrokolloids : Stabilisatoren, Dickungs- und Gehermittel in Lebensmittel, Band 2 der Schriftenreihe Lebensmittelchemie, Lebensmittelqualitat, Behr's VerlagGmbH & Co., Hamburg, 1996. The encapsulation is a well known process to a person skilled in the art, and may be performed, for instance, using techniques such as spray-drying, agglomeration or yet extrusion ; or consists of a coating encapsulation, including coacervation and complex coacervation techniques. Generally speaking, by "perfumery base" we mean here a composition comprising at least one perfuming co-ingredient. Said perfuming co-ingredient is not of the formula (I). Moreover, by "perfuming co-ingredient" it is meant here a compound, which is used in perfuming preparation or composition to impart a hedonic effect. In other words such a co-ingredient, to be considered as being a perfuming one, must be recognized by a person skilled in the art as being able to impart or modify in a positive or pleasant way the odor of a composition, and not just as having an odor. The nature and type of the perfuming co-ingredients present in the base do not warrant a more detailed description here, which in any case would not be exhaustive, the skilled person being able to select them on the basis of its general knowledge and according to intended use or application and the desired organoleptic effect. In general terms, these perfuming co-ingredients belong to chemical classes as varied as alcohols, aldehydes, ketones, esters, ethers, acetates, nitriles, terpene hydrocarbons, nitrogenous or sulphurous heterocyclic compounds and essential oils, and said perfuming co-ingredients can be of natural or synthetic origin. Many of these co-ingredients are in any case listed in reference texts such as the book by S. Arctander, Perfume and Flavor Chemicals, 1969, Montclair, New Jersey, USA, or its more recent versions, or in other works of a similar nature, as well as in the abundant patent literature in the field of perfumery. It is also understood that said co-ingredients may also be compounds known to release in a controlled manner various types of perfuming compounds. Generally speaking, by "perfumery adjuvant" we mean here an ingredient capable of imparting additional added benefit such as a color, a particular light resistance, chemical stability, etc. A detailed description of the nature and type of adjuvant commonly used in perfuming bases cannot be exhaustive, but it has to be mentioned that said ingredients are well known to a person skilled in the art. An invention's composition consisting of at least one compound of formula (I) and at least one perfumery carrier represents a particular embodiment of the invention as well as a perfuming composition comprising at least one compound of formula (I), at least one perfumery carrier, at least one perfumery base, and optionally at least one perfumery adjuvant. It is useful to mention here that the possibility to have, in the compositions mentioned above, more than one compound of formula (I) is important as it enables the perfumer to prepare accords, perfumes, possessing the odor tonality of various compounds of the invention, creating thus new tools for their work. Its is also understood here that, unless otherwise indicated or described, any mixture resulting directly from a chemical synthesis, e.g. without an adequate purification, in which the compound of the invention would be involved as a starting, intermediate or end-product could not be considered as a perfuming composition according to the invention. Furthermore, the invention's compound can also be advantageously used in all the fields of modern perfumery to positively impart or modify the odor of a consumer product into which said compound (I) is added. Consequently, a perfumed article comprising: i) as perfuming ingredient, at least one compound of formula (I) or an invention's composition; and ii) a consumer product base, is also an object of the present invention. For the sake of clarity, it has to be mentioned that, by "consumer product base" we mean here a consumer product which is compatible with perfuming ingredients. In other words, a perfumed article according to the invention comprises the functional formulation, as well as optionally additional benefit agents, corresponding to a consumer product, e.g. a detergent or an air freshener, and an olfactive effective amount of at least one invention's compound. The nature and type of the constituents of the consumer product do not warrant a more detailed description here, which in any case would not be exhaustive, the skilled person being able to select them on the basis of its general knowledge and according to the nature and the desired effect of said product. Examples of suitable consumer products include solid or liquid detergents and fabric softeners as well as all the other articles common in perfumery, namely perfumes, colognes or after-shave lotions, perfumed soaps, shower or bath salts, mousses, oils or gels, hygiene products or hair care products such as shampoos, body-care products, deodorants or antiperspirants, air fresheners and also cosmetic preparations. As detergents there are intended applications such as detergent compositions or cleaning products for washing up or for cleaning various surfaces, e.g. intended for textile, dish or hard-surface treatment, whether they are intended for domestic or industrial use. Other perfumed articles are fabric refreshers, ironing waters, papers, wipes or bleaches. Some of the above-mentioned consumer product bases may represent an aggressive medium for the invention's compound, so that it may be necessary to protect the latter from premature decomposition, for example by encapsulation. The proportions in which the compounds according to the invention can be incorporated into the various aforementioned articles or compositions vary within a wide range of values. These values are dependent on the nature of the article to be perfumed and on the desired organoleptic effect as well as the nature of the co-ingredients in a given base when the compounds according to the invention are mixed with perfuming co- ingredients, solvents or additives commonly used in the art. For example, in the case of perfuming compositions, typical concentrations are in the order of 0.01 % to 5 % by weight, or even more, of the compounds of the invention based on the weight of the composition into which they are incorporated. Concentrations lower than these, such as in the order of 0.01% to 2% by weight, can be used when these compounds are incorporated into perfumed articles. The invention's compounds can be easily prepared by esterification of the corresponding acids, which are also described in the above-mentioned prior art. The invention will now be described in further detail by way of the following examples, wherein the abbreviations have the usual meaning in the art, the temperatures are indicated in degrees centigrade (0C) ; the NMR spectral data were recorded in CDCl3 (if not stated otherwise) with a 360 or 400 MHz machine for 1H and 13C, the chemical displacements δ are indicated in ppm with respect to TMS as standard, the coupling constants J are expressed in Hz.

Example 1

Preparation of a perfuming composition

A perfuming composition of the "floral-ylang-woody and chypre" type was prepared by admixing the following ingredients :

Ingredient Parts by weight Benzyl acetate . 15 Linalyl acetate 50 Styrallyl acetate 5 Aldehyde C I l undecylic 2 10%*Cetaloxφ l) 1 Citron Sfuma essential oil 20 Ethylvanilline 1 Eugenol 2 Exaltolide® 2) 30 Geranium essential oil 20 Hedione® 3) 50 Iralia® Total 4) 50 Lilyflore® 5) 2 Mousse moss 1 Muscenone Delta ' 2 1%* Paracresol • 2 Phenethylol 50 Polysantol® 7) 2 P-Tert-Butylcyclohexyl acetate 50 Benzyl salicylate 90 Clary-sage essential oil 5 Vertofix® Cffiur 8) 30 Ylang Extra 20 500

* in dipropyleneglycol 1) Dodecah.ydro-3a,6,6,9a-tetramethyl-naphtho[2,l-b]furan; origin: Firmenich SA, Geneva, Switzerland 2) Pentadecenolide; origin: Firmenich SA, Geneva, Switzerland 3) Methyl dihydrojasmonate; origin: Firmenich SA, Geneva, Switzerland 4) Mixture of isomers of methylionones; origin: Firmenich SA, Geneva, Switzerland 5) 2,5-Dimethyl-2-indanmethanol; origin: Firmenich SA, Geneva, Switzerland 6) 3-Methyl-4/5-cyclopentadecen-l-one; origin: Firmenich SA, Geneva, Switzerland 7) 3,3-Dimethyl-5-(2,2,3-trimethyl-3-cyclopenten-l-yl)-4-penten -2-ol; origin: Firmenich SA, Geneva, Switzerland 8) Methyl cedryl ketone; origin International Flavors & Fragrances, USA

The addition of 5 parts by weight of ethyl 4,6,6-trimethyl-l,3-cyclohexadiene-l- carboxylate to the above-described perfuming composition imparted to the fragrance of the latter an harmonious spicy note of the natural saffron type, which transformed the chypre aspect in a positive manner, providing thus a richer and more natural fragrance. Said effect could not be obtained by the addition of any of the compounds cited in EP 955290. Furthermore, the addition of the same amount of Safranal to the above- described perfuming composition, in view of obtaining the same saffron note, resulted in a polarized fragrance having a medicinal aspect.