Regiochemical control in the alkylation of tetrahydroindanones

Abstract

The first regiospecific alkylation of the 3a,4,7,7a-tetrahydroindanone (1) has been achieved, by use of a phenylthio group acting as a directing group for enolate anion generation or as a blocking group which permits the formation of the regioisomeric enolate anion. The stereochemical outcome of the process has been determined for alkylation with methyl iodide, allyl bromide, and methyl bromoacetate. Additionally the alkylation of the enolate anion has been compared to that of the equivalent O-silylated enolate. The difference in stereochemistry may reflect a balance between steric and stereoelectronic effects.