THE SENSITIZED PHOTOOXYGENATION OF METHYL SUBSTITUTED 1,2-DIPHENYLCYCLOBUTENES

Article abstract of DOI:10.1016/S0040-4020(01)96577-9

A series of Me substituted 1,2-diphenylcyclobutenes was subjected to dye-sensitized photooxidation in the presence of methylene blue.In the case of the 3,3-dimethyl-, 3,3,4-trimethyl- and 3,3,4,4-tetramethyl-1,2-diphenylcyclobutenes, the sensitized oxidations are accompanied by ring-contraction with concomitant ortho hydroxylation of one aromatic nucleus.When electron transfer induced photooxidation techniques utilizing 9,10-dicyanoanthracene (DCA) as a sensitizer are employed with the series of Me substituted diphenylcyclobutenes, the reactions take a markedly different course and a broad spectrum of oxidation products are obtained including, most notably, ozonides of the cyclobutenes.The mechanisms of these conversions are addressed and the significance of the results discussed.