Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Patent
1997-01-15
1998-06-02
Reamer, James H.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
568390, 568379, C07C 6732
Patent
active
057602778
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to field of organic synthesis. It concerns, in particular, a process for the preparation of unsaturated cycloaliphatic ketones of formula ##STR5## having two conjugated double bonds in positions 1 and 3, or 2 and 4, such as indicated by the dotted lines, and wherein R defines a C.sub.1 to C.sub.3 alkyl radical.
PRIOR ART
The compounds of formula (I) are useful as intermediates for the preparation of jasmonic derivatives having well appreciated odor properties and amongst which there can be cited more particularly methyl dihydrojasmonate (Hedione.RTM., registered trademark of Firmenich SA). Since its discovery, this latter compound has been the object of a great Theimer, Academic Press, 1982! and the interest of the perfumers for this compound has increased these last few years, following the development of preparation methods which make it possible to obtain the preferred cis isomer.
The method employed for the industrial manufacture of methyl dihydrojasmonate is characterized by a first step which consists of the 3,158,644 and Helv. Chim. Acta 20, 1474 (1937)!, a reaction which leads to the formation of 2-pentylidenyl-cyclopentanone, which compound is then isomerized into 2-pentyl-cyclopent-2-enone. This latter compound, when added upon of dimethyl malonate and decarboxylated, leads to a mixture of methyl dihydrojasmonate consisting essentially of the cyclanic trans isomer.
On the other hand, cis-methyl dihydrojasmonate has been prepared according to the literature via hydrogenation of methyl 3-oxo-2-pentyl-cyclopent-2-ene-acetate in the presence of aluminum isomerizing distillation of the trans compound in the presence of a carbonate of an alkaline or alkaline-earth metal. The major inconvenient of such processes resides in the fact that they only allow the formation of the desired compound in the form of a mixture wherein the content in cis isomer does not generally go beyond 30%.
DESCRIPTION OF THE INVENTION
The present invention provides a novel solution to the problem of an industrial production, which is both straightforward and economical, of methyl dihydrojasmonate, in the form of the cis or trans isomer, as well as its lower homologue or nor-methyl dihydrojasmonate.
The process of invention is oriented towards the preparation of a diene cyclopentanone of formula (I), more particularly in its isomeric form of formula ##STR6##
We observed that the aldol condensation in basic medium of an aldehyde of formula R--CH.dbd.CH--CHO, wherein the double bond has an (E) configuration, with the cyclopentanone gave rise to the formation of dienones (Ia) and not, as might have been expected, to that of the allylic carbinols of formula ##STR7##
When the diene ketones (Ia), having an (E,E) type configuration, are subjected to thermal treatment at a temperature comprised between about 200.degree. and 450.degree. C., they convert into their isomers (Ib) having an endocyclic double bond and a (Z) configuration double bond in position 1 of the side chain. Now, it is precisely in this particular configuration that the compounds obtained by the process of the invention preferably react with dimethyl malonate for the subsequent step of the process for obtaining methyl dihydrojasmonate, or its lower homologue, following the reaction scheme hereafter: ##STR8##
Both the addition of the dimethyl malonate and its decarboxylation take place according to methods analogous to those described in the literature
As regards the hydrogenation, it can be carried out in the presence of palladium on charcoal to provide an equimolar mixture of methyl dihydrojasmonate or nor-jasmonate, in their trans and cis isomeric forms.
One of the major advantages of the synthetic approach suggested by the present invention resides in the fact that, thanks to the cycloaliphatic ketones prepared by the process described, it is possible to prepare, through a judicious choice of the hydrogenation method, just as well the mixtures rich in cis isomer, as those containing essentially the trans isomer.
Th
REFERENCES:
patent: 2069861 (1937-02-01), St. Pfau
patent: 2088021 (1937-07-01), Wickert et al.
patent: 2957027 (1960-10-01), Beets et al.
patent: 3158644 (1964-11-01), Demole
E. Piers et al., "Five-membered ring spiro-annulation via thermal rearrangement of enol silyl ethers of 2-(cyclopropylmethylene)cycloalkanones. A formal total synthesis of some spirovetivane-type sesquiterpenoids", Can. J. Chem., vol. 61 (1983) pp. 288-297.
E. Demole, "The Fragrance of Jasmine", Fragrance Chemistry, Academic Press, Inc. (1982), pp. 349-396.
Helv. Chim. Acta 20 (1937) p. 1474.
Muyaiyama et al, Chemical Abstracts, vol. 87, No. 5490r, 1977.
Ishihara et al, Chemical Abstracts, vol. 83, No. 78672d, 1975.
Decorzant Rene
Naef Ferdinand
Firmenich SA
Reamer James H.
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