Acid-catalyzed rearrangement of aryl-substituted homobenzoquinone epoxides.
The BF3-catalyzed reactions of diphenyl-substituted and endo-monophenyl-substituted homobenzoquinone epoxides proceeded through a regioselective oxirane ring opening followed by participation of a pi-aryl transannular cyclization to give the tricyclic diketo alcohols. The conformationally semirigid ethano-bridged diphenyl-substituted homologues also provided similar diketo alcohols and the subsequent ring-expanded cycloheptenedione (via a subsequent 1,2-acyl migration associated with cyclopropane ring opening), depending on the methyl-substitution pattern of the quinone frame. However, the exo-monophenyl-substituted and the rigid biphenyl-2,2'-diyl-substituted homobenzoquinone epoxides essentially remained unchanged.
Asahara
H
H
Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
Kubo
E
E
Togaya
K
K
Koizumi
T
T
Mochizuki
E
E
Oshima
T
T