Alkylation Reactions of 2-Methylpropyl 3-(2-Methylpropoxy)-5-oxocyclohex-3-ene-1-carboxylate

Abstract

The anion derived from 2-methylpropyl 3-(2-methylpropoxy)-5-oxocyclohex-3-ene-1-carboxylate was reacted with methyl iodide to give cis and trans isomers of 2-methylpropyl 6-methyl-3-(2-methylpropoxy)-5-oxocyclohex-3-ene-1-carboxylate. The reaction proceeded with high regioselectivity. A combination of n.m.r. experiments was used to determine that the major diastereoisomer was in a trans configuration. The dianion derived from 2-methylpropyl 3-(2-methylpropoxy)-5-oxocyclohex-3-ene-1-carboxylate methylated at C1 and C6 with a roughly equal proportion of cis and trans isomers. When treated with 1 equiv. of 1-bromo-3-chloropropane the same dianion alkylates at C1 to give 2-methylpropyl 1-(3-chloropropyl)-3-(2-methylpropoxy)-5-oxocyclohex-3-ene-1-carboxylate.