Synthesis of 3,4-Bis(benzylidene)cyclobutenes

The syntheses of several derivs. of 3,4-bis(benzylidene)cyclobutene I-V are reported. Previously unknown 1,2-dibromo-3,4-bis(benzylidene)cyclobuteneIII-V were obtained through in situ generation of 1,6-diphenyl-3,4-dibromo-1,2,4,5-tetraene followed by electrocyclic ring closure. Ensuing redn. and metal-catalyzed cross-coupling provided addnl. derivs. The effects of ring strain on the geometry and electronics of these derivs. were examd. by X-ray crystallog. and 1H NMR spectroscopy, resp. [on SciFinder(R)]