Biphenylenes. Part XIX. Reactions of mono- and di-methoxybiphenylenes and related compounds

Abstract

Monosubstitution occurs at the adjacent β-position on nitration of 2-acetamido-, 2-acetoxy-, and 2-methoxy-biphenylene, Claisen rearrangement of 2-allyloxybiphenylene, formylation of 2-hydroxy- and 2-methoxy-biphenylene, and Friedel–Crafts acetylation of 2,6- and 2,7-dimethoxybiphenylene. Oxidation of 2-hydroxybiphenylene gives unstable 2,2′-bi(biphenylenyl)-3,3′-quinone. Bromination of 2-methoxybiphenylene gives the 3-bromoderivative which with more bromine gives 2,2′,4-tribromo-5-methoxybiphenyl. Bromination of 2,3-dimethoxy-biphenylene gives first biphenylene-2,3-quinone and then its 1,4-dibromo-derivative, whereas 2,6- and 2,7-dimethoxybiphenylene simply give the corresponding dibromo-substitution products even with an excess of bromine. 2,7- and 1,8-Dimethoxybiphenylene are demethylated by treatment with methylmagnesium iodide and with boron tribromide respectively.