Pyrolysis selenophenes

Monocyclic Selenophens.—Ring-closures. The Fiesselmann reaction has been applied to the synthesis of selenophens. The reaction of (500) with sodium selenide and ethyl bromoacetate thus gave (501). ° Also the Gewald reaction is successful cyclohexanone reacts with ethyl cyanoacetate and selenium in the presence of base to give (502). 2,5-Diarylselenophens are obtained, together with small amounts of the 2,4-isomer, on heating 4-aryl-1,2,3-selenadiazoles. Upon pyrolysis of (503) at 250 C the selenophen derivative (504) is formed. "... 

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