Biphenylenes. Part XXV. 2-Benzoylbiphenylenes and the synthesis of biphenylene-2-boronic and 2,6-(or 2,7-)diboronic acid

Abstract

Nitration of 2-benzoylbiphenylene gives a mononitro-derivative, but bromination gives an inseparable mixture of mono- and di-bromo-compounds. Pure 2-benzoyl-6-bromo- and 2-benzoyl-6,7-dibromo-biphenylene have been prepared by treating sulphonated benzoylbiphenylene with bromine, and 2-benzoyl-7-bromobiphenylene has been made by benzoylation of 2-bromobiphenylene. The Baeyer–Villiger oxidation of these bromo-2-benzoylbiphenylenes has been studied. A reinvestigation of the Beckmann rearrangement of the oxime of 2-benzoylbi-phenylenes has shown that both possible isomeric amides are formed. The oxime of 2-benzoyl-6,7-dibromobiphenylene in the Beckmann reaction gave the anilide of 6,7-dibromobiphenylene-2-carboxylic acid.The reaction of biphenylene with boron tribromide and aluminium chloride or bromide followed by hydrolysis gave biphenylene-2-boronic acid and a diboronic acid, probably the 2,6-derivative.