H. Bekkum, B. Graaf, G. V. Minnen‐Pathuis
Sep 2, 2010
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Journal
Recueil des Travaux Chimiques des Pays-Bas
Abstract
1-t-Butylcyclohexanecarboxylic acid (1) has been synthesized from t-butyl-cyclohexanols as well as from 2-(1-methylcyclohexyl)-2-propanol by the Koch -Haaf carboxylation. A side product in these preparations is 2-methyl-2-(1-methylcyclohexyl)propionic acid (5). Details are given for the preparation of the cis- and trans-isomers of 2-, 3-and 4-t-butylcyclohexanecarboxylic acid (cis- and trans-2, 3 and 4) starting from the corresponding t-butylbenzoic acids. The t-butylbenzoic acids and their methyl esters have been hydrogenated over transition metal catalysts at 25°. Palladium differs from platinum, rhodium and ruthenium by, in all cases, giving in excess the most stable isomer. In the hydrogenation of 2-t-butylbenzoic acid over rhodium desorbed 6-t-butyl-1-cyclohexene-1-carboxylic acid is shown to be the main source of the trans-2 formed. The mass spectra of 1 − 4 are presented and discussed. The mode of fragmentation of cis-4 and cis-3 was found to differ in a characteristic way from that of their trans-isomers.