CH628024A5 - Process for preparing 3,7-dimethyl-2-octenenitrile - Google Patents

Description

The present invention relates to a process for the preparation of 3,7-dimethyl-2-octenitrile having the formula (II)

better known as geranonitrile, with respect to which they have a sweeter scent and greater chemical stability.

60 In this regard, it should be noted that while geranonitrile is treated for a few days at room temperature with a mixture of 98% H2S04 and glacial CH3COOH 5/25 vol. it gives rise following the addition of water to the formation of slightly volatile pious substances, the compound II, saturated in 6-7, remains practically unchanged.

The process for the preparation of 3,7-dimethyl-2-octenenitrile according to the invention is characterized in claim 1 above.

3

628024

Another important application of the above compounds consists in their use as intermediates in numerous organic syntheses.

Example 1

5.28 g of 3,7-dimethyl-3-hydroxy-6-octenitrile in 25 cc of hexane, added with 0,52 g of palladium on carbon at 5% by weight, are hydrogenated under stirring, in a glass apparatus, at ambient temperature and with a hydrogen pressure of 760 ± 100 mm Hg absolute.

The absorption of stoichiometric hydrogen with respect to the saturation of the IV double bond lasts about an hour.

At the end, the catalyst is filtered and the solvent is evaporated under vacuum, recovering the 3,7-dimethyl-3-hydroxyoctane-nitrile (I) with a conversion and selectivity higher than 90%.

By subsequent vacuum distillation with Vigreux, a product and purity —98% is obtained which boils at 83-4 ° C at 0.3 mm Hg.

Example 2

Compound I is obtained with the same ratios between the reactants of Example 1, but by carrying out hydrogenation in an autoclave of steel with an initial hydrogen pressure of 8.6 kg / cm2.

The recovery and purification methods of the product are identical to the previous example.

Example 3

2 g of 3,7-dimethyl-3-hydroxy-octanonitrile (I) and 3 g of basic Woelm aluminum oxide are kept for 220 minutes at 220-230 ° C in nitrogen stream in a glass flask equipped of water-cooled bubble condenser.

At the end, the mixture is left to cool to room temperature, the reaction mass is taken up with ethyl ether and filtered, thus completely evaporating the solvent.

Thus 3.7-dimethyl-2-octenitrile (II) is obtained - consisting of a mixture of eis and trans isomers in a ratio of -45 / 55 with conversion and selectivity of 90%.

Product II can be obtained 98% pure approx. subjecting the previous residue to vacuum distillation and collecting the boiling product at 52-53 ° C at 0.1 mmHg.

The characterization of the compounds in question was carried out by IR, NMR and mass analysis.

The IR spectrum confirms the presence of the following functional groups:

OH 3460 cmJ

C = N unconjugated 2252 cm-1 C - O of a tertiary alcohol 1153 cm-1

io = C - H

= C = N conjugated in a

C = C conjugate = C - H (stretching)

3045 cm-1 2215 cm-1 1630 cm-1 700 cm-1

compound (I)

compound (II)

15 The NMR analysis (solvent CC14, internal standard HMDS) has highlighted the following characteristic signals:

- OH

- CH2- (2) 20 - CH2- (4)

- CH; C

- CH,

- CH,

(5,6)

25

30

35

CH3 ~ CH,

3.23 ppm 2.42 ppm

1.45 ppm

1.24 ppm

0.83 ppm compound (I)

= ch

5.03 ppm

- ch2- (4)

2.08 ppm

- ch3 eis (or trans)

1.98 ppm

- ch3 trans (or eis)

1.85 ppm

- ch2- (6)!

1.50 ppm

- ch2- (5) /

- c «^

1.20 ppm ch3

0.81 ppm

CH,

compound (II)

40

Mass spectrometry confirms the molecular weights (169 for I and 151 for II) and the respective postulated structures.

v

Claims (6)

628024 2 CLAIMS 1. Procedure for the preparation of 3,7-dimethyl-2 - obtainenitrile having formula (II) CH. 4 CH 4 CH, 5 CH, • CH THE CN 10 \ 6 CH, 7 CH (II) (II) 15 CH3 8 3 said process being characterized in that the 3,7-dimethyl-3-hydroxy-6-obtainers are hydrogenated in the presence of a hydrogenation catalyst to obtain the 3,7-dimethyl-3-hydroxy-octanonitrile having formula (I) 7 CH OH3 8 T = H3 20 The intermediate compound in the process claimed in claim 1 is 25 4 CH 5 CH 30 35 4 CH 5 CH (THE) 3,7-dimethyl-3-hydroxy-octane-nitrile of formula (I) and the compound thus obtained is dehydrated in the presence of a dehydration catalyst at temperatures ranging from 220 ° C to 230 ° C in an inert gas environment to obtain formuia (II) 3,7-dimethyl-2-obtainenitrile in the form of a mixture of "eis" and "trans" isomers. 2. Process according to claim 1, characterized in that said hydrogenation catalyst is metallic palladium. 3. Process according to claim 1, characterized in that said dehydration catalyst is a basic aluminum. 4. 3,7-dimethyl-2-octenitrile (II) obtained by the process according to claim 1. Use of the 3,7-dimethyl-2-octenitrile (II) according to claim 4, in perfuming compositions for soap and cosmetics. 40 The compounds in question - and in particular II - have a pleasant characteristic odor which makes them possible to use as perfumes and more particularly for the formulation (together with other known products) of perfumed mixtures that can be used in soaps, cosmetics, deodorants and similar. In this sense, among other things, they can advantageously replace 3,7-dimethyl-2,6-octenitrile (III) 50 55 TO X CN (IH)