Aromatization of 1,4-Dihydrobenzocycloalkenes, 1,4-Dihydronaphthocycloalkenes, and Related Systems

Article abstract of DOI:10.1021/jo01297a019

A series of methyl-substituted 1,4-dihydrobenzenes has been prepared, and the rates of oxidation of these molecules by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) have been measured.Existing evidence points to the involvement of a positively charged intermediate which is formed as an ion pair in an initial rate-limiting hydride transfer to DDQ.Series of cycloalkyl-fused 1,4-dihydrobenzenes and 1,4-dihydronaphthalines (fused 1,2 and 2,3) have been prepared and the rates of their DDQ induced aromatization have been studied.The results are explained on the basis of inductive effects associated with the size of the fused ringand exocyclic vs. endocyclic bond order preferences.