C1C2 bond cleavage in vinylidenecyclopropanes: Theoretical density functional theory study

Abstract Density functional calculations at the B3LYP/6‐31G* level were carried out to investigate the photo rearrangements in 1,1‐diarylvinylidene‐2,3‐dimethyl‐ and 1,1‐diarylvinylidene‐2,2,3,3‐tetramethylcyclopropanes. Among the five different routes considered, none except the one leading to the final products of butatriene derivatives (route 4) was found to be able to explain the experimental findings only. However, the route 4 points out on the involvement of the C1C2 bond cleavage in strained cyclopropane ring. Thus, a new mechanism that results in successive transformations was suggested to explain this distinct C1C2 bond cleavage in cyclopropane ring for both precursors leading to formation of butatriene derivatives. The results of calculations indicate that photochemistry of vinylidenecyclopropane derivatives is significantly different than in the case of methylenecyclopropane compounds. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004