Cyclopropanation reactions with α, β-epoxy diazomethyl ketones and rearrangement of α, β-epoxy cyclopropyl ketones

Abstract

The cyclopropanation reactions of α, β-epoxy diazomethyl ketones 1 with olefins using Pd(OAc) 2 as catalyst is described. Differently substituted epoxy diazo ketones 1a- 1f give with cyclohexene exo-norcarane derivatives. 3, 3-Diphenyloxiranyl-2 diazomethyl ketone 1a reacts with olefins like isobutene, E- and Z- butene-2 to give epoxy cyclopropyl ketones. 3, 3-Diphenyloxiranyl-2 cyclopropyl ketones 2a and 9 undergo two consecutive rearrangement reactions with BF 3 as catalyst. In the first step an epoxide rearrangement of 9 takes place to give β-ketoaldehyde 10, which in a second step rearranges to enolester 12. The latter reaction is most likely restricted to β-ketoaldehydes which have a quaternary α-C atom. A rationale for this unusual reaction has been proposed.