N-ALKOXYIMIDES AND O-ALKOXYAMINES

The invention relates to a method for the preparation of a cyclic N-alkenyloxyimide by treatment of a cyclic N-hydroxyimide with an alkenylating agent. Such a method for the preparation of 0- substituted hydroxyimides is known for example from JP-A- 59.122.465. In JP-A-59.122.465 N-hydroxy-5-norbornene-2,3- dicarboxyimides are converted into O-substituted N- hydroxy-norbornene-2,3-dicarboxyimides with the aid of RX, (with X being halogen) or R ₂ S0 ₄ , it being stated that besides alkyl, alkynyl, aryl, betaketoalkyl, substituted phenyl or substituted pyridyl, R could also be alkenyl. Thus, in that case N-alkenyloxy-norbornene-2,3- dicarboxyimides would be obtained.

It has, however, been found that with the method described here it is not possible to prepare cyclic N- alkenyloxyimides.

A general drawback of this known method for the preparation of O-substituted hydroxyimides is that a useless halide salt or sulphate is formed upon O- substitution, which represents an environmental burden. A further drawback of the known method is that when alkenyl halides are used, measures must be taken to prevent these readily evaporating and toxic substances from escaping; sulphuric acid esters are carcinogenic.

It is the aim of the invention to avoid the above-mentioned drawbacks.

This aim is achieved in that a vinyl carboxylic acid ester or a vinyl ether is used as alkenylating agent in the method for the preparation of cyclic N- alkenyloxyimides by treatment of cyclic N-hydroxyimides

with an alkenylating agent and in that the treatment takes place in the presence of a suitable metal-containing catalyst.

An added advantage is that this transvinylation only gives rise to the formation of a carboxylic acid or an alcohol that is biodegradable and that can optionally be recovered as a useful byproduct.

It is generally known to use protective groups for protection of the nitrogen when nitrogen-containing compounds are subjected to alkenylation reactions. A method that is often used when alkoxyamines are prepared is, for example, protection of the nitrogen in the form of oximes, hydroxamic acids or N-hydroxyimides. However, it has been found that when, for example, ketoximes or hydroxamic acids are used instead of cyclic N- hydroxyimides in the method according to the invention, the target product is not obtained.

It has been found that under the influence of a suitable metal-containing catalyst cyclic N- alkenyloxyimides are selectively obtained as products in the method according to the invention starting from cyclic N-hydroxyimides with a vinyl carboxylic acid ester or a vinyl ether. With a suitable choice of catalyst, solvent and optionally a cocatalyst a conversion of more than 70% can be achieved. Surprisingly, there are hardly any side- reactions such as the decomposition of vinyl acetate into an aldehyde.

The cyclic N-hydroxyimides to be used can be obtained by reacting for example hydroxylamine with an anhydride. For N-hydroxyphthalimide this is described for example in JP-A-53.144.571.

Examples of suitable alkenylating agents are vinyl esters or alkyl- or arylvinyl esters of carboxylic acids, with 4-15 carbon atoms, for example vinyl acetate, α- or β-methyl vinyl acetate, α- or β-benzylvinyl acetate vinyl propionate, vinyl butanoate, etc. Preferably vinyl

acetate is used as alkenylating agent.

Suitable metal-containing catalysts are for example metals of group 9 or 10 of the new IUPAC version of the periodic system as represented in the table printed on the cover of the Handbook of Chemistry and Physics, 70th Edition, CRC Press, 1989-1990. Preferably a palladium-containing catalyst, in particular palladium (II) acetate is used. The amount of palladium-containing catalyst is usually 0.001-5 mol%, calculated relative to the amount of cyclic N-hydroxyimide.

There is also advantage in using a cocatalyst besides the metal-containing catalyst in the transvinylation, optionally in combination with a suitable organic acid. Suitable cocatalysts are for example (di)phosphines, diamines, (di)phosphonites,

(di)phosphinites, (di)phosphites and combinations thereof. Examples of suitable organic acids are p-toluene sulphonic acid, trifluoro acetic acid, trifluoro sulphonic acid, etc. Usually use is made of 0-10 mol% of for example tributyl or triphenyl phosphine, tetra-methylene diamine, 2,2 '-bipyridine, o-phenanthroline, bis.dimethyl or phenylphosphino)methane or -ethane, tributyl or triphenyl phosphite, calculated relative to the amount of cyclic N- hydroxyimide. Preferably an amount of cocatalyst is used which is eguivalent to the amount of metal-containing catalyst used.

The amount of alkenylating agent to be used will in practice usually lie between 1 and 1.2 equivalents, calculated relative to the amount of N-hydroxyimide. Preferably, an equivalent amount or a small excess of alkenylating agent is used.

The transvinylation is usually carried out in the presence of organic solvents such as aliphatic or aromatic hydrocarbons, halogenated aliphatic or aromatic hydrocarbons and ethers. Examples of suitable solvents are toluene, xylene, vinyl acetate, acetonitrile,

tetrahydrofuran (THF) and methyl tert. butyl ether (MTBE).

The reaction temperature may vary within wide limits. In practice the reaction temperature will usually be between 50 and 150°C, preferably at reflux temperature. For practical considerations the reaction will mostly be carried out at atmospheric pressure; however, it is also possible to carry out the reaction at elevated pressure.

Cyclic N-alkenyloxyimides may serve among other things as intermediates in the synthesis of cyclic N- alkoxyimides and N-alkoxyamines. The invention therefore also relates to cyclic N-alkenyloxyimides, with alkenyl standing for ethenyl, isopropenyl or n-propenyl, for example N-alkenyl-oxyphthalimides, N- alkenyloxysuccinimides, N-alkenyl- oxytetra- or N-alkenyloxyhexahydrophthalimides, 2- alkenyloxy-3a, 4, 7, 7a-tetrahydro-4,7-methano-lH- isoindole-l,3(2H)-diones and 2-alkenyloxy-3a, 4, 7, 7a- tetrahydro-4,7-epoxy-lH-isoindole-l,3(2H)-diones.

Perjessy, A., Sidόova, E. , Chem. Pap. 39(6), pp. 755-761, (1985), does mention a cyclic N-alkenyloxide, viz. 2-(ethenyloxy)-3a,4,7a-tetrahydro-4,7-epoxy-lH- isoindole-1,3(2H)-dione, but this article in no way indicates how such a substance could be prepared, nor is this otherwise clear to one skilled in the art. The invention also relates to the hydrogenation of cyclic N-alkenyloxyimides to cyclic N-alkoxyimides using a suitable hydrogenation catalyst.

The reason for this is that, surprisingly, it has been found that the hydrogenation of cyclic N-alkenyl- oxyimides obtained according to the transvinylation as described above takes place selectively at the vinyl group, and the N-0 bond is not broken. Optionally, the crude reaction mixture obtained after the transvinylation reaction can be used without previous purification such as the removal of catalyst residues.

The hydrogenation catalyst used may be one of

the known hydrogenation catalysts. An example of a suitable hydrogenation catalyst is a palladium-containing catalyst with 0.5-10 wt.% palladium, calculated relative to the amount of carbon. The amount of palladium/carbon catalyst to be used is mostly 0.1-10 wt.%, preferably 1-5 wt.%, of a 1-5 wt.% palladium/carbon catalyst, calculated as the amount of palladium/carbon relative to the amount of N-alkenyloxyimide.

The pressure at which the hydrogenation reaction is carried out is not critical. The hydrogenation reaction will usually be carried out at 0.1-10 MPa. Preferably, the hydrogenation reaction will be carried out at a pressure of 0.5-1 MPa.

The hydrogenation is usually carried out in the presence of a solvent. Examples of suitable solvents are water, alcohols, ethers, hydrocarbons, for example toluene, THF, ethanol and methanol.

The invention also relates to the following new compounds: N-alkoxysuccinimides, N-alkoxytetra- and N- alkoxyhexahydrophthalimides, with alkoxy standing for ethoxy, n-propyloxy or isopropyloxy.

The invention also relates to the preparation of N-alkoxyamines from cyclic N-hydroxyimides via transvinylation with a vinyl carboxylic acid ester or a vinyl ether under the influence of a palladium-containing catalyst followed by hydrogenation of the resulting cyclic N-alkenyloxyimide under the influence of a hydrogenation catalyst, after which the resulting cyclic N-alkoxyimide is converted to the corresponding N-alkoxyamine in a known manner. The cyclic N-alkoxyimide obtained can for example by means of hydrolysis or hydrazinolysis be converted to N-alkoxyamine. Another possibility is the so-called hydroxylamine exchange in which hydroxylamine sulphate and caustic, for instance NaOH or KOH, are used to obtain, besides the alkoxyamine, the N-hydroxyimide used as starting material.

The invention will now be elucidated with reference to the following examples without however being limited thereto.

Example I

N-hvdroxyphthalimide

To phthalic anhydride (45.5 g, 0.307 mol) in 80 ml water at room temperature simultaneously a 33% hydroxylamine sulphate solution (75 ml, 0.307 mol) and 25% sodium hydroxide solution (49 ml, 0.307 mol) was dosed in 1 hour 's time. After this the reaction mixture was heated to 90°C during 1 hour and then cooled down to room temperature. The precipitate formed was filtered off and air-dried. 43.1 g of light-yellow powder (N- hydroxyphthalimide) was obtained (85%).

Example II N-vinyloxyphthalimide

Tributyl phosphine (60 μl, 0.26 mmol) was added under nitrogen to a solution of palladium acetate (58 mg, 0.25 mmol) in 16 ml toluene. 4 g (0.025 mol) N- hydroxyphthalimide was added at once, followed by vinyl acetate (3 ml, 0.03 mol). The mixture was heated to 80°C for two hours. Precipitated catalyst residues were removed by filtering the reaction mixture over Celite.

After boiling down of the filtrate a solid product was obtained. Yield: 3.33 g N-vinyloxyphthalimide (70%), besides non-converted N-hydroxyphthalimide.

^-NMR (CDC1 ₃ , 200 MHz) : δ = 4.44 (dd, IH) ; 4.68 (dd, IH) :

6.70 (dd, IH); 7.7-7.9 (m, 4H) .

Example III

N-vinyloxyphthalimide

N-hydroxyphthalimide (4 g; 0.025 mol) and vinyl acetate (3 ml; 0.03 mol) was heated to 60°C in acetonitrile (16 ml). Subsequently, palladium acetate (75 mg; 0.33 mmol), dissolved in acetonitrile (3 ml), was added dropwise in 0.5 hour's time. Afterwards, stirring was applied for two hours at 60°C. Filtration of the catalyst residues over Celite followed by boiling down of the filtrate yielded 3.6 g N-vinyloxyphthalimide (75%).

Example IV

Hydrogenation of N-vinyloxyphthalimide

N-vinyloxyphthalimide (5 g; 0.026 mol) was dissolved in 20 ml toluene followed by addition of 50 mg Pd/C (5%). After three nitrogen purges, the reaction mixture was placed under a hydrogen atmosphere at 20 MPa and room temperature. After about 90 minutes no more hydrogen absorption was measured. The pressure was relieved and the autoclave was purged three times with nitrogen. Subsequently the catalyst was filtered off and the filtrate boiled down. Yield: 5.05 g N- ethoxyphthalimide (quantitative conversion, 100%). ^ ^■ H-NMR (CDC1 ₃ , 200 MHz) : δ = 1.42 (t, 3H) ; 4.29 (9, 2H) : 7.72-7.89 (m, 4H) .

Example V

N-vinyloxysuccinimide

N-hydroxysuccinimide (5 g; 0.0435 mol) was added to a solution of palladium acetate (100 mg, 0.435 mmol) and vinyl acetate (5.4 ml, 0.057 mol) in 14 ml toluene and

6 ml acetonitrile.

The reaction mixture was heated to 80°C for one hour, cooled and the catalyst residues were filtered off over a layer of Celite. After boiling down of the filtrate 4.3 g

N-vinyloxysuccinimide was obtained: (70%).

^X H-NMR ( CDCI ₃ , 200 MHz ) : δ = 2 . 81 ( S , 4H ) ; 4 . 47 ( dd , IH) : 4 . 58 ( dd , IH ) 6 . 57 ( dd , IH ) .

Example VI N-vinyloxyhexahydrophthalimide

N-hydroxyhexahydrophthalimide (3 g; 0.0178 mol) was dissolved in 10 ml toluene. After addition of palladium acetate (20 mg, 0.089 mmol) and vinyl acetate (2.04 ml; 0.0213 mol) the mixture was heated to 80°C for 2 hours. The reaction mixture was then filtered off over

Celite and the filtrate boiled down. The N-vinyloxy-cis- hexahydrophthalimide yield was 2.6 g (75%).

^-NMR (DMSO, 200 MHz) : δ = 1.27-1.5 (m, 4H) ; 1.55-1.9 (m, 4H); 3.04-3.19 (m, 2H) : 4.39 (dd, IH) 4.6 (dd, IH): 6.76 (dd, IH) .

Example VII N-hvdroxytetrahvdrophtalimide

Hydroxyamine sulphate (162 g; 0.985 mol) was dissolved in 500 ml water at room temperature.

Subsequently, tetrahydrophthalic anhydride (300 g, 1.97 mol) was added and a 50% sodium hydroxide solution (158 g, 1.97 mol) was dosed in three quarters of an hour. This caused the temperature to rise to about 45°C. After all the sodium hydroxide had been added, the material was heated to 90°C for two hours. After cooling to room temperature, everything was crystallized out. After filtration, washing with small portions of water, and air- drying of the precipitate, 332 g monohydrate was obtained (91%).

^X H-NMR (DMSO, 200 MHz) : δ = 2.09-256 (m, 4H) ; 3.1 (m, 2H); 5.88 (m, 2H).

Example VIII N-vinylo ytetrahvdrophthalimide

N-hydroxytetrahydrophthalimide (3 g, 0.0167 mol) was dissolved in 10 ml toluene. Palladium acetate (20 mg, 0.08 mmol) and vinyl acetate (2.05 ml; 0.022 mol) was added and the reaction mixture was heated to 80°C for one hour. This was followed by cooling and filtration of the catalyst residue over a layer of Celite. After boiling down of the filtrate 1.7 g (40%) N- vinyloxytetrahydrophthalimide was obtained.

Example IX N-ethoxyamine

N-ethoxytetrahydrophthalimide (15 g, 0.078 mol) was suspended in 50 ml water at 55°C. After addition of hydroxyl amine sulphate (6.4 g; 0.039 mol), followed by dropwise addition of 50% sodium hydroxide solution (12.5 g, 0.156 mol) for one hour and two hours' after-reaction at 55°C, followed by heating and distilling over of 20 ml distillate (boiling range 65-102°C), a distillate was obtained which contained 2.7 g ethoxya ine (83%). The bottom product was then acidified to pH 3 using concentrated hydrochloric acid. The N- hydroxytetrahydrophthalimide was filtered off and could be reused: yield 10.4 g (80%).