Internuclear cyclisation. Part XXXI. Cyclisation of 2-(N-alkyl-N-phenylcarbamoyl)phenyl radicals: formation of cyclohexadienones and cyclohexadienyl iodides by scavenging of the spiro-γ-lactam intermediate

Abstract

A comparative survey has been made of the products of homolytic decomposition of 2-(N-alkyl-N-phenyl-carbamoyl)benzenediazonium fluoroborates under a variety of conditions, and of those of photolysis of the corresponding N-alkyl-2-iodobenzanilides. Copper-catalysed decomposition of the diazonium salts in acetone purged with oxygen gives cyclohexadienones, the yields of which reflect the extent of radical cyclisation to γ-lactam intermediates. Decomposition of the diazonium salts induced by sodium iodide in methylene chloride containing a little added iodine gives cyclohexadienyl iodides, structures of which have been established by Ag⁺-catalysed methanolysis to cyclohexadienyl methyl ethers, and/or by photolysis, which gives cyclohexadienyl dimers.