Di‐Π‐Methane Rearrangement

Abstract

This reaction, known as the Zimmerman rearrangement, di‐π‐methane rearrangement, di‐π‐methane photorearrangement, or di‐π‐methane reaction, is a photochemical reaction of a molecular entity comprising two π‐systems separated by a saturated carbon atom (a sp 3 carbon, e.g. a methylene group) involving the migration of one π‐moiety bonded to the saturated carbon to other π‐moiety accompanied by the concomitant formation of a cyclopropane ring from the remaining π‐moiety and methylene group. This rearrangement has been reported to consist at least six versions and all these variants differ from each other. This rearrangement has high regiospecificity with a strong preference for migration of the less conjugated π‐moiety to the more conjugated one. This rearrangement has proven valuable in preparation of substituted cyclopropanes.