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Rhodium-Catalyzed Isomerization and Alkyne Exchange Reactions of 1,4-Dithiins via the 1,2-Ethenedithiolato Rhodium Complex

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journal contribution
posted on 13.09.2018, 17:38 by Mieko Arisawa, Kyosuke Sawahata, Takuya Ichikawa, Masahiko Yamaguchi
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.