Synthesis of triphenylene and dibenzopyrene derivatives: Vanadium oxytrichloride a novel reagent

This paper presents an efficient synthetic procedure for the preparation of various triphenylene and dibenzopyrene derivatives using VOCl3 as a novel reagent. Symmetrically substituted hexaalkoxytriphenylenes are obtained from o-dialkoxybenzenes by oxidative trimerization with VOCl3 in high yields. The oxidative coupling of a 3,3',4,4'-tetraalkoxybiphenyl and 1,2-dialkoxybenzenes or 1,2,3-trialkoxybenzenes affords unsymmetrically substituted derivatives of triphenylene. The reagent oxidizes 3,3',4,4'-tetraalkoxybiphenyl efficiently to 2,5,6,9,12,13-hexaalkoxydibenzo[fg,op]naphthacene-1,8-quinone and its 1,10-quinone isomer. Both the quinones can be converted to liquid crystalline derivatives using well-established chemistry. Effects of solvent, reagent concentration, acid catalyst and temperature have been studied.