Patent GB-309911-A (GB)
Title: A process for the production of cyclohexene aldehydes, and cyclohexene carboxylic acids, which contain at least one dialkylated ring carbon atom
Filed: 1929-04-11
Abstract: 309,911. Soc. Anon. M. Naef et Cie. April 17, 1928, [Convention date]. Unsaturated hexamethylene aldehydes, carboxylic acids and esters.-Cyclohexene aldehydes and carboxylic acids, which contain at least one dialkylated ring carbon atom, are prepared by interaction of butadienes, which have a dialkylated carbon atom at one or both ends of the conjugated double bond, with acrolein or acrylic acid or their alkyl derivatives under pressure and at elevated temperature, preferably 150-200‹ C. In most cases the product comprises a mixture of two isomers which can be separated by converting the less sterically-hindered isomer into a bisulphite compound if an aldehyde or into an ester if an acid. The products are useful as perfumes or in the manufacture of perfumes. Examples are given of the condensation of:-(1) 1 : 1 : 3-trimethylbutadiene with acrolein and crotonaldehyde to give trimethyl- and tetramethylcyclohexene aldehydes, and with acrylic acid to yield trimethylcyclohexene carboxylic acids; (2) 1 : 1-dimethylbutadiene with acrolein and crotonaldehyde to form dimethyl- and trimethyl-cyclohexene aldehydes; (3) 1:1:4:4-tetramethylbutadiene and acrolein and crotonaldehyde to produce tetramethyl- and pentamethyl-cyclohexene aldehydes. Specification 300,130 is referred to. The Specification as open to inspection under Sect. 91 (3) (a) also describes the preparation of cyclohexene aldehydes by heating butadiene and its homologues in general under pressure and at elevated temperature with acrolein and its homologues. Replacement of the acrolein component by acids homologous with acrylic acid, or their esters, gives rise to the corresponding cyclohexene carboxylic acids and their esters. Again, by substituting the corresponding acetylenic aldehydes, acids or esters for the above-mentioned olefinic aldehydes, acids or esters, there are obtained cyclohexadiene aldehydes, carboxylic acids and esters. In most of these condensations also, the formation of two isomeric products occurs, the separation of which is effected by converting the less sterically-hindered isomer into a bisulphite or semicarbazide if an aldehyde or into an ester if an acid. Stereoisomers can be similarly separated. These products, too, are useful as perfumes or in the manufacture of perfumes. Thus, the aldehydic products, or the carboxylic products after reduction, may be condensed with ketones, such as acetone and methylethyl ketone, to give compounds of the irone series. Examples are given of the condensation of:-(1) isoprene with acrolein, crotonaldehyde, 2-ethylacrolein 2: 2- dimethylacrolein and a-methyl-#-ethylacrolein to form the corresponding alkyl-cyclohexene aldehydes; isoprene with acrylic acid and crotonic acid to give methyl- and dimethyl-cyclohexene carboxylic acids; isoprene with tetrolic aldehyde to produce a dimethyl-cyclohexadiene aldehyde; (2) 1:1: 3-trimethylbutadiene with crotonaldehyde to give tetramethyl-cyclohexene aldehydes, and its oxidation to give an acid identical with that resulting from the condensation of 1: 1 : 3- trimethylbutadiene with crotonic acid; the methyl ester of this acid is not saponifiable and the acid is therefore a derivative of cyclogeranic acid; (3) 1 : 1-dimethyJbutadiene with tetrolic aldehyde to form a trimethyl-cyclohexadiene aldehyde; (4) 2: 3-dimethylbutadiene with acrolein and crotonaldehyde to give dimethyl- and trimethyl-cyclohexene aldehydes, and with propargyl aldehyde to form a dimethyl-cyclohexadiene aldehyde; (5) 1:1:3-trimethylbutadiene with propargyl aldehyde to produce a trim.&thyI-oycJohexadiene aldehyde. (6) 1: 1:4-trimethylbutadiene acrolein and crotonaldehyde to form trimethyl- and tetramethyl-cyclohexene aldehydes. Propiolic acid and its homologues mav be employed as the acid component. The semi-carbazones of some of the aldehydic products are mentioned. Reference is also made to the condensation with acetone of the product from 1 : 1- dimethylbutadiene and crotonaldehyde to produce irone. This subject-matter does not appear in the Specification as accepted.