A GENERAL SYNTHETIC ROUTE TO MESOGENIC HETEROCYCLES - PYRROLES, THIOPHENE DIOXIDES AND PYRIDAZINES

A general route to potentially mesogenic heterocycles, based on 1-(4-bromophenyl) and 1-(4'-bromobiphenyl)-1,4-dioxoalkanes is described and used to prepare pyrroles, thiophene 1,1-dioxides and pyridazines. No mesogenic compounds were obtained in the pyrrole and thiophene 1,1-dioxide series, but four new mesogenic pyridazines, 3-hexyl-6-(4-bromophenyl)pyridazine, 3-hexyl-6-(4'-bromobiphenyl)pyridazine, and the two corresponding cyano-derivatives (obtained by copper-catalysed displacement of bromine by cyanide) were prepared and their mesophase behaviour is described. The mesophase behaviour of some synthetic intermediates including 4'-bromobiphenyl vinyl ketone and several 1-(4'-bromobiphenyl)-1,4-dioxoalkanes is also described.