Stilbenes from Sulfur-Mediated Dehydrodimerization of Substituted Toluenes

Article abstract of DOI:10.1021/jo00010a017

When provision is made for removal of coproduct hydrogen sulfide, the reaction of sulfur with methyl p-toluate (MPT; 1) at 280 deg C leads to 70+percent yields of the product dimethyl trans-4,4'-stilbenedicarboxylate (DMSC, 2) if conversion of the MPT is restricted to ca 10percent.Diphenyl ether or excess MPT serves as the reaction solvent.Other products of the reaction include dimethyl 4,4'-bibenzyldicarboxylate (DBD, 3), 1,2,3-tris(4-carbomethoxyphenyl)propane (4), 1,2,3-tris(4-carbomethoxyphenyl)propene (5; mixture of E and Z isomers), and 2,3,4,5-tetrakis(4-carbomethoxyphenyl)thiophene (6).The products are consistent with the reversible formation of 4-carbomethoxybenzyl radicals from sulfur and MPT where removal of the hydrogen sulfide drives the reaction forward.