Effects of Halogen Substiution on Reactions of o-Quinol Acetates with Isopropylmagnesium Bromide and Diisopropylmagnesium. Competition between Unimolecular Decomposition and Bimolecular Reactions of Radical Anions

Article abstract of DOI:10.1021/jo00352a009

When a single methyl substituent at C-2 or C-4 of an o-quinol acetate (1) is replaced by a halogen atom, a greatly decreased yield of the corresponding 3-isopropylphenol is obtained from reaction of 1 with isopropylmagnesium bromide.Replacement of a second methyl group by halogen results in a marked increase in the yield of the 3-isopropylphenol.Essentially identical product distributions are obtained from reactions of halogenated o-quinol acetates with concentrated and dilute Grignard solutions and with diisopropylmagnesium, in contrast to reactions with halogen-free o-quinol acetates.Reactions with hexadeuterioisopropylmagnesium bromide gave reduction products bearing increasing percentages of deuterium at C-3 as the number of bromines on the rings of the ω-quinol acetates increased.These data are consistent with reactions of halogenated o-quinol acetates, in contrast to those of halogen-free analogues, proceeding solely by SET processes.The reactions of halogen-stabilized radical anions with isopropyl radicals compete with decomposition of radical anions to phenoxy radicals.