1.3- Dithiins acetylene derivs

Krespan and McKusick have studied the addition reaction of dithietenes to various oleflnes and acetylenes. Thus, the reaction of 3,4-bis(trifluoromethyl)-l,2-dithiete (378) with DMAD gives a dithiin derivative (379), which loses sulfur on heating to give 2,5-dicarbomethoxy-4,5-bis(trifluoromethyl)thiophene (380) [Eq. (57)]. 

Dithiins.—A new synthesis of 1,3-dithiins from aromatic aldehydes, acetylenes, and HjS has been described. Carbenoids react with 1,2-dithia-acenaphthene to afford the insertion product (22 R = Ph or tosyl). Pyrolysis of the ditosyl derivative yields the ketone (22 RR = O). 

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