Electron Transfer Resulting from Excitation of Contact Charge Transfer Complexes of Some Styrene Derivatives and Oxygen. The Role of Oxygen as an Electron Acceptor

Abstract

Abstract Irradiation of contact charge transfer (CCT) bands (320–370 nm) of 4-methoxystyrene (1a) and 4-methylstyrene (1b) with molecular oxygen in acetonitrile and benzene resulted in the formation of the corresponding cis- and trans-1,2-diarylcyclobutanes (2 and 3) as well as benzaldehydes (4), oxidative cleavage products. In the case of 1b, 7-methyl-1-(4-tolyl)-1,2,3,4-tetrahydronaphthalene (5) and 6-methyl-4-(4-tolyl)-1,2,3,4-tetrahydronaphthalen-1-one (6) were also afforded. The formation of these products is reasonably explained by electron transfer in the excited CCT pair followed by addition of the resulting 1 cation radical to ground-state 1 to form a dimer cation radical; its cyclization leads to the dimeric products and trapping of a cyclic dimer cation radical by oxygen affords ketone 6.