Hydroboration-Oxidation of Benzocycloalkenes

Abstract

The products of the hydroboration-oxidation of the benzocycloalkenes (1 ; n = 1-5) with diborane and thexylborane have been studied. With indene, diborane yields 86% of indan-2-ol and thexylborane yields 99%. Each of the other benzocycloalkenes gives approximately 90% of the α-alcohol with diborane, and increasing amounts (10-38%) of the β-alcohol with thexylborane. Electronic factors are suggested to be paramount to explain the difference between indene and the other alkenes. A number of rearrangement reactions have been encountered during the synthesis of the alkenes.