Benzoyl isoselenocyanate

A solitary example of this type of ring formation is provided by the reaction of diphenyl-diazomethane with benzoyl isoselenocyanate, which gives the benzo[6 ]selenophene derivative (199) (80JOC4366). 

The imino heterocycle 55 reacts with benzoyl isoselenocyanate via a [2+2] cycloaddition sequence to give aryl-(4-seleno-4//-pyrido[l,2-a]pyrazin-3-yl)amines 56... 

Examples of well-established 1,3,4-thiadiazole syntheses have been extended to the production and study of their selenium analogues." 1,4-Disubstituted selenosemicarbazides (191 R = Aik, Ar, or Ac) are readily accessible in good yield by the addition of isoselenocyanate esters (including benzoyl isoselenocyanate) to acylhydrazines." Their cyclization in acidic media affords the stable crystalline 1,3,4-selenadiazoles (192 R = Aik, Ar, or Ac) " the members of the aroylamino-series are stable to alkalis, but are hydrolysable by acids to the parent amines (192 R = H) these are convertible into conventional derivatives, as expected." Bis-selenoureas of type (194) are similarly accessible, but usually cyclize spontaneously to the substituted 2,5-dianilino-1,3,4-selenadiazoles (195). The action of acetic anhydride on (194) yields diacetyl derivatives of (195)... 

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