Degenerate β-Aryl Rearrangements in Photochemically Generated Triarylvinyl Cations

Article abstract of DOI:10.1021/jo00191a023

Irradiation of triphenyl- (1a), tri-p-tolyl (1b),or tri-p-anisylvinyl bromide (1c) in methanol gave the vinyl ethers 4 and the phenanthrenes 5.A study of <2-13C>-labeled bromides showed that β-aryl rearrangements takes place in the photochemically generated vinyl cations 3*.Irradiation of triaryl<2-13C> bromides 1* in trifluoroethanol and analysis of the extent of scrambling from C-2 to C-1 in the trifluoroethyl vinyl ethers 8 showed 38percent, 72percent, and 92percent rearrangement of the 13C label for 1a*, 1b*, and 1c*, respectively.Similar irradiation of 1* in methanol resulted in no rearrangement in 4.The results are discussed in relation to the nature of the solvent, the stability of the triarylvinyl cations, and the migratory aptitudes of the aryl groups.The behavior of the photochemically and thermally generated ions was compared.