Rhodium-catalyzed isomerization and alkyne exchange reactions of 1,4-dithiines occurred by cleavage of two C-S bonds. The 2,5- and 2,6-disubstituted 1,4-dithiins underwent isomerization reactions in toluene at 110 °C, providing equilibrium mixtures of isomers. At 150 °C, the reaction of 1,4-dithiins and dimethyl acetylenedicarboxylate gave unsymmetric 2,3-di(methoxycarbonyl)-1,4-dithiins and 2,3-di(methoxycarbonyl)thiophenes, the latter of which were formed by desulfurization of the 1,4-dithiins. A related reaction of the alkyne and a 1,2-dithiete gave a 2,3-di(methoxycarbonyl)thiophene. These reactions are considered to involve 1,2-ethenedithiolato rhodium intermediates.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry