Acid-catalysed isomerization of ethyl 5-Hydroxy-7a-methyl-1-oxo-2,6,7,7a tetrahydro-1H-indene-4-carboxylate

Abstract

Treatment of a chloroform solution of ethyl 5-hydroxy-7a-methyl-1-oxo- 2,6,7,7a-tetrahydro-1H-indene-4-carboxylate with dry hydrogen chloride at room temperature gave ethyl 5-hydroxy-7a-methyl-1-oxo-cis-3a,6,7,7a- tetrahydro-1H-indene-4-carboxylate, and the corresponding trans-hydrindan in the ratio 9 : 1. Hydrogenation of this mixture gave ethyl 5-hydroxy-7a-methyl-1-oxo-cis-3a,6,7,7a-tetrahydroindan-4-carboxylate, and ethyl t-7a-methyl-1,5-dioxo-r-3a,4,5,6,7,7a-hexa-hydroindan-c-4a- carboxylate, which were characterized by conversion into the cis and trans isomers of 7a-methylperhydroindan-1,5-dione, respectively.