Stereochemistry of the (2′-Vinylcyclopropyl)cyclobutane Rearrangement. Photochemical 1,3 Addition of Benzene to 3,4-Substituted Cyclobutenes

Abstract

Thermal isomerization of cis-4,5-dimethyl-endo-tetracyclo[5.3.0.02,10.03,6]decene-8 (IX) at 300° gave rise to endo, cis-8,9-dimethyltricyclo[2.2.1.04,10]deca-2,5-diene (XII) as the major isomeric product. The reaction, which is a typical (2′-vinylcyclopropyl)cyclobutane rearrangement, thus proceeds with retention of the stereochemistry at the migrating σ bond. Arguments are presented to show that this rearrangement is distinct from the homo [1,5] sigmatropic shift which in the tricyclo[3.3.0.02,8]octene-3 systems involves the migration of hydrogen atoms only. It is also distinct from, although related to, the vinylcyclopropane rearrangement. The use of the (2′-vinylcyclopropyl)cyclobutane rearrangement in synthesis is exemplified by the preparation of endo-tetracyclo[8.2.1.02,6.-077,13]trideca-3,8,11-triene (VII) from benzene and 1,3,5-cycloheptatriene in three steps. © 1972, American Chemical Society. All rights reserved.