Production process of cyclohexenyl ketones

Details Production process of cyclohexenyl ketones Production process of cyclohexenyl ketones

2001-06-07

2004-11-23

Badio, Barbara P. (Department: 1616)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

Reexamination Certificate

active

06822121

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a production process of intermediate starting materials used for perfumery, more specifically, 2-cyclohexenyl methyl ketones (1b) and 1-cyclohexenyl methyl ketones (1c), or mixtures thereof.
BACKGROUND OF THE INVENTION
2,6,6-Trimethylcyclohexenyl methyl ketone is a useful compound as an intermediate for the synthesis of fruity floral fragrant materials such as &agr;- and &bgr;-damascone. Damascones typified by &agr;-damascone which serves as a key note component of natural roses have been commercially produced and practically used as an important fruity floral fragrance. Damascones have three double-bond-depending isomers as described below. These Isomers have their own odor notes, respectively, while they have a fruity floral note basically. They are used differently according to their application purposes.
A large number of production processes for these damascones {&dgr;-damascone (2a), &agr;-damascone (2b), &bgr;-damascone (2c)} have been reported, for example, in “Review” (Shigeru Torii, et al., Koryo, No. 125, 47-60 (1979)). Among them, a production process of &agr;-Damascone (2b), &bgr;-Damascone (2c), &dgr;-Damascone (2a) represented by the following reaction
wherein any one of dotted lines means a double bond, which was reported by K. Subrahmania {J. C. S. Perkin 1, 1, 727(1975)}, is known as a process focusing on to the Aldol reaction of 2,6,6-trimethylcyclohexenyl methyl ketone (1).
2,6,6-Trimethyl-3-cyclohexenyl methyl ketone (1a), which is one of the starting materials of the above-described reaction, is synthesized by the Diels-Alder reaction between 1,3-pentadiene (4) and mesityl oxide (5) as shown in the following reaction scheme:
On the other hand, 2,6,6-trimethyl-2-cyclohexenyl methyl ketone (1b) is prepared by the following process, that is, by the Diels-Alder reaction of isobutene (6) and 4-methyl-3,5-hexadien-2-one (7).
2,6,6-Trimethyl-1-cyclohexenyl methyl ketone (1c) is synthesized by the following reaction of ethylene (8) with 3-acetyl-2,4-dimethyl-1,3-pentadiene (9).
However, a process for synthesizing methyl-substituted-cyclohexenyl methyl ketones represented by the formulas (1b) and (1c) by isomerization of the double bond of the compound represented by the formula (1a) is not known yet.
Since &agr;- and &bgr;-damascones which are typical fruity-floral fragrant materials are expensive, there is a demand for the development of a low-cost production process therefore. The above-described production process of damascones by Subrahmania has a merit in its fewer production steps based on the Aldol reaction of 2,6,6-trimethylcyclohexenyl methyl ketones {(1b) and (1c)} with acetaldehyde. It is however difficult to industrially produce 4-methyl-3,5-hexadien-2-one (7) and 3-acetyl-2,4-dimethyl-1,3-pentadiene (9), the starting materials for the production of 2,6,6-trimethylcyclohexenyl methyl ketones {(1b) and (1c)}. Production of them also needs high costs. The above-described process is therefore not used industrially from the economical viewpoint. An object of the present invention is therefore to provide a more economical process for producing 2,6,6-trimethylcyclohexenyl methyl ketones {(1b) and (1c)}, that is, intermediates for the synthesis of &agr;- and &bgr;-damascones.
SUMMARY OF THE INVENTION
Under the above-described conditions, the present inventors have carried out an extensive studies and, as a result, it has been found that methyl-substituted cyclohexenyl methyl ketones represented by (1b) and/or (1c), which are starting materials for the synthesis of &agr;- and/or &bgr;-damascone, can be prepared economically by isomerization of methyl-substituted cyclohexenyl methyl ketone represented by the formula (1a).
In the present invention, there is thus provided a process for producing a 2-cyclohexenyl methyl ketone represented by the formula (1b), a 1-cyclohexenyl methyl ketone represented by the formula (1c), a trans-3-cyclohexenyl methyl ketone represented by the formula (1a′), or a mixture thereof, which comprises isomerizing, in the presence of an isomerizing catalyst, a 3-cyclohexenyl methyl ketone represented by the formula (1a).
wherein, R
1
, R
2
and R
3
each independently represents a hydrogen atom or a methyl group and at least two of R
1
, R
2
and R
3
represent a methyl group.


REFERENCES:
patent: 3914242 (1975-10-01), Boshagen et al.
patent: 4334098 (1982-06-01), Mookherjee et al.
patent: 3003894 (1981-08-01), None

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