ALKYLATION REACTIONS OF 2-METHYLPROPYL 2-METHYLPROPOXY)-5-OXOCYCLOHEX-3-ENE-1-CARBOXYLATE

The anion derived from 2-methylpropyl 2-methylpropoxy)-5-oxocyclohex-3 -ene-1-carboxylate was reacted with methyl iodide to give cis and tran s isomers of 2-methylpropyl -methylpropoxy)-5-oxocyclohex-3-ene-1-carb oxylate. The reaction proceeded with high regioselectivity. A combinat ion of n.m.r. experiments was used to determine that the major diaster eoisomer was in a trans configuration. The dianion derived from 2-meth ylpropyl 2-methylpropoxy)-5-oxocyclohex-3-ene-1-carboxylate methylated at C 1 and C 6 with a roughly equal proportion of cis and trans isome rs. When treated with 1 equiv. of 1-bromo-3-chloropropane the same dia nion alkylates at C 1 to give 2-methylpropyl -methylpropoxy)-5-oxocycl ohex-3-ene-1-carboxylate.