Regioselective synthesis of α,α-dialkylcyclopentanones from 1-hydroxycyclobutanecarboxylic acid or from O-protected cyclobutanone cyanohydrin

Abstract

1-(1-Hydroxyalkyl)cylobutanols 4a-f, readily available either from 1-hydroxycyclobutane carboxylic acid or from O-protected cyclobutanone cyanohydrin, appeared the most suitable precursors for a regioselective synthesis of cyclopentanones α,α-disubstituted with various similar or different alkyl, alkenyl, aryl or cycloalkyl groups. The key steps consist of acid or Grignard reagent induced C 4→C 5 ring expansions.