A series of diformylbenzophenones were generated by sequentially reacting protected bromobenzaldehydes with n-butyllithium and ethyl N, N-dimethylcarbamate. The acetal protective groups were cleaved with refluxing formic acid. Vilsmeier–Haack formylation of 2, 2′, 4, 4′-tetramethoxybenzophenone also afforded a related dialdehyde. MacDonald “2+ 2” condensation of three benzophenone dialdehydes with a dipyrrylmethane gave ...
