Biphenylenes. Part XXII. Reactions of 1,2,7,8-tetramethoxy-4,5-dimethyl- and 2,3,6,7-tetramethoxybiphenylene and of 1,6,7,8-tetramethoxybiphenylene-2,3-quione

Abstract

Substitution occurs at the vacant β-positions on bromination and nitration of 1,2,7,8-tetramethoxy-4,5-dimethyl-biphenylene. On treatment with aqueous ethanolic nitric acid, the biphenylene oxidative demethyl-ation to give 1,7,8-tetramethoxy-4,5-dimethylbiphenylene-2,3-quinone.

The dioxime of 1,6,7,8-tetramethoxybiphenylene-2,3-quinone, on treatment with alkali, gives the 6,7,8,9-tetramethoxy-derivative of the new ring-system, biphenyleno[2,3-c]furazan.

The mono-oxime of 6,7-dimethoxybiphenlene-2,3-quione undergoes a second-order Beckmann rearrangement to give a derivative of benzocyclobutene, Bromination and nitration of 2,3,6,7-tetramethoxybiphenylene lead to the formation of 1,4-dibromo- and 1-nitro-6,7-dimethoxybiphenylene-2,3-quione respectively.

The structure of some deeply coloured complexes formed by polymethoxybiphenylenes with halogens and with acidic reagents is discussed.