Reactions of phenylbromoacetylene with heterocumulenes in the presence of iron pentacarbonyl

Reactions of phenylbromoacetylene with heterocumulenes in the presence of iron pentacarbonyl have been studied. The reactions with arylcarbodiimides gave diazepinone derivatives in 41–17% yields. The reaction with phenyl isocyanate gave two hydantoin derivatives, in 18 and 8% yields. On the other hand, the reaction with diphenylketene was not catalysed by iron pentacarbonyl and gave 2-bromo-3,4-diphenyl-1-diphenylacetoxynaphthalene. In all cases coupling of phenylbromoacetylene to give diphenylbutadiyne was also observed. Reaction mechanisms are discussed.