The present invention relates to 2-alkyl-cis-3-pentenoates and novel isomeric mixtures containing greater than 50% of C.sub.2 -C.sub.6 alkyl-2-methyl-cis-3-pentenoates produced by interalia novel processes; and to compositions using such mixtures of isomers of alkyl-2-methyl-3-pentenoates to alter the flavor and/or aroma of consumable materials.
There has been considerable work performed related to substances which can be used to impart (or enhance) flavors to (or in) various consumable materials. These substances are used to diminish the use of natural materials, some of which may be in short supply and to provide more uniform properties in the finished product. Fruity, sweet, fresh, berry, pineapple, green, herbaceous, strawberry and pear aromas, as well as fruity, berry, woody, green and pear tastes are particularly desirable for many uses in foodstuff flavors, chewing gum composition flavors and medicinal product flavors. Fruity, peppery, woody, green, herbaceous, strawberry and chamomile notes and nuances are desirable in perfume compositions. Notes having Turkish-like characteristics, as well as aromatic, sweet and bitter notes are desirable in tobacco-flavoring compositions.
U.S. Pat. No. 3,449,769 issued on Mar. 10, 1970 discloses processes for imparting a fresh fruity flavor (particularly strawberry flavor) to foods by adding a small amount of 2-methyl-2-pentenoic acid to the foodstuff. In U.S. Pat. No. 3,449,769 it is emphasized that the basic nuance imparted by 2-methyl-2-pentenoic acid is a "berry" flavor. Quite unexpectedly, the novel "high cis" isomeric mixtures of the instant invention has properties different in kind from the 2-methyl-2-pentenoic acid of U.S. Pat. No. 3,499,769, which is only fruity and strawberry like, but does not have the sweet, pineapple, green, herbaceous and pear aroma and taste qualities of the isomeric ester mixture of the instant invention nor does it have the chamomile nuances so useful in perfumes. Isomeric ("cis" and "trans") mixtures of 2-methyl-3-pentenoic acid containing greater than 50% cis isomer are disclosed in co-pending application for U.S. Pat. No. 490,717 filed on July 22, 1974 and abandoned application No. 408,854 filed on Oct. 23, 1973 to have the following organoleptic properties:
a. In food flavorings, a sweet, fruity, strawberry, winey-cognac, butter-like, rum-like and butterscotch aroma and a sweet, strawberry, nutty-coconut, fatty, butter-like, rum-like, and butterscoth-like taste with fruity, coconut-like isovaleric undertones; PA1 b. In perfumes, green, sweet, sharp strawberry notes; and PA1 c. In tobaccos, aromatic, sweet, bitter, slightly woody and smokey notes giving tobacco a "Turkish-like" character. PA1 i. French Pat. No. 1,389,856, issued Feb. 19, 1965; PA1 ii. Brewis and Hughes, Chem. Communications, (8), 157-8 (1965); PA1 iii. Bordenca and Marsico, Tetrahedron Letters (16), 1541-3 (1967); and PA1 iv. Hosaka and Tsuji, Tetrahedron, 27, (16) 3821-9 (1971). PA1 b. Palladium-on-carbon; or PA1 c. Palladium-on-calcium carbonate (Lindlar catalyst) at a temperature in the range of from about 10.degree. C up to about 100.degree. C; a hydrogen pressure in the range of from about 5 psig up to about 80 psig, the concentration of said catalyst, based on weight of the starting material, the alkyl-2-methyl-3,4-pentadienoate being from about 0.1% up to about 10%; then recovering a chemical from the reaction mass which contains at least 60% by weight of one or more alkyl-2-methyl-cis-3-pentenoates having the structure: ##STR8## Then, optionally, separating the ingredients of the resulting chemical composition to obtain highly refined ethyl-2-methyl-cis-3-pentenoate (up to 100% alkyl-2-methyl-cis-3-pentenoate) and/or then, optionally, forming one or more carboxylic acids by means of admixing the resulting chemical composition or the hydrogenation reaction product with a basic hydrolysis agent which may be either an aqueous solution of alkali metal hydroxide, or an alcoholic solution of an alkali metal hydroxide and re-esterifying the resulting carboxylic acid by means of reacting same with an esterifying agent such as an alkanol in the presence of a protonic acid catalyst. PA1 i. 2-methyl-3-pentynoic acid; and PA1 ii. 2-methyl-2,3-pentadienoic acid PA1 Parahydroxy benzyl acetone PA1 Vanillin PA1 Maltol PA1 Ethyl-3-methyl-3-phenyl glycidate PA1 Benzyl acetate PA1 Ethyl butyrate PA1 Methyl cinnamate PA1 Methyl anthranilate PA1 Alpha-ionone PA1 Gamma-undecalactone PA1 Diacetyl PA1 Anethole PA1 Cis-3-hexenol PA1 2-(4 -hydroxy-4-methyl pentyl) norbornadiene (prepared according to Example II of application for U.S. Pat. No. 461,703 filed on Apr. 17, 1974) PA1 Beta-ionone PA1 Isobutyl acetate PA1 Dimethyl sulfide PA1 Acetic acid PA1 Acetaldehyde PA1 4-(2,6,6-trimethyl-1,3-cyclohexadien-1-yl)-2-butanone (prepared according to Example XVI of application for U.S. Pat. No. 386,320 filed on Aug. 7, 1973) PA1 4-(6,6-dimethyl-2-methylene-3-cyclohexen-1-yl)- 2-butanone (prepared according to Example XVI of application for U.S. Pat. No. 386,320 filed on Aug. 7, 1973) PA1 Geraniol PA1 Ethyl pelargonate PA1 Isoamyl acetate PA1 Naphthyl ethyl ether PA1 Ethyl acetate PA1 Isoamyl butyrate PA1 2-Methyl-2-pentenoic acid PA1 2-Methyl-3-pentenoic acid PA1 Elemecine (4-allyl-1,2,6-trimethoxy benzene) PA1 Isoelemecine (4-(1-propenyl)-1,2,6-trimethoxy benzene
Isomeric mixture of 2-methyl-3-pentenoic acid were shown to have been prepared by Boorman and Linstead, J. Chem. Soc. 1935, 258-67 (abstracted by Chem. Abstracts, Vol. 29, pages 2912 (7/8 ). 2-Ethyl-3-pentenoic acid is shown to be prepared by Fichter and Obladen, Berichte, 42, 4703-7 by distillation of alpha-ethyl gamma methyl paraconic acid which, in turn, is formed by reduction using a sodium-mercury amalgam of ethyl-alpha-ethyl aceto-succinate. The above-disclosed processes produce isomer mixtures which are considered to be different in kind insofar as their organoleptic properties are concerned from the isomer mixtures produced by the processes of the instant invention.
Ethyl-2-methyl-3-pentenoate (95% 3:1 trans:cis and 5% ethyl-2-methyl-2-pentenoate) is being offered as a development chemical by Toray Industries, Inc. of 2, Nihonbashi-Muromachi 2-chome, Chuo-Ku, Tokyo, Japan. This mixture of esters is not found to be of interest as a flavor material.
McGreer, et al. Can. J. Chem., 41, 726-31 (1963) discloses the production of various alkyl esters of pentenoic and butenoic acids by means of pyrolysis of 3,5-dimethyl-3-carbomethoxy .DELTA..sup.1 -pyrazoline. Thus, on page 728 of the McGreer article, having the following structures are shown to be produced: ##STR2##
Tsuji, et al. J. Am. Chem. Soc., 86, (20) 4350-3 (1964) discloses the production of alkyl alkenoates by means of reaction of carbon monoxide, alkenyl halides and alkanols with use of palladium chloride as a catalyst. Other methods for the synthesis of alkyl alkenoates are set forth in the following references:
None of the above references sets forth a process for preparing the cis isomer of an alkyl pentenoate of mixtures containing more than 50% cis isomer.
Felkin, et al. Ann. Chem. (Paris) 6 (1), 17-26 (1971) discloses processes for producing "high cis" and "high trans" methyl-2-methyl-3-pentenoate mixtures, according to the following reaction sequences: ##STR3## A process for preparing the "high cis" acid mixture is set forth in Felkin, et al. "Chemical" Communications, No. 802, pages 75 and 76 (Dec. 29, 1965).
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