Reaction of 1-substituted indenes with diborane or N-bromoacetamide in protic solvents. The effect of the substituent on the stereochemistry of addition

Abstract

The reaction of 1-substituted Indenes with diborane or N-bromoacetamide (NBA) in protic solvents has been investigated to determine the effect of an increase of steric bulk of the substituent on the stereochemical course of addition. In the hydroboration reaction the proportion of the products via attack by diborane from the less hindered side increases, as the steric bulk of the substituent at C-1 increases. The reaction with NBA in aqueous dioxan, followed by acetylation, gave a mixture of 3-substituted-1-acetoxy-2-bromoindans with trans,trans and trans,cis-configuration: 1-phenylindene gave mainly trans,trans-1-acetoxy-2-bromo-3-phenylindan, while trans,cis-1-acetoxy-2-bromo-3-methylindan was the major product in the case of 1-methylindene.