Acylarylnitrosamines. Part IX. Use of benzyne promoters in the conversion of N-nitrosoacetanilide into benzyne

Abstract

N-Nitrosoacetanilide (NNA), and hence benzenediazonium acetate, decomposes in solution to give benzyne and/or phenyl radicals. Tetraphenylcyclopentadienone diverts the decomposition to give benzyne mainly, while furan, despite being an arynophile, diverts the reaction towards phenyl radicals. The addition of 1,1-diphenylethylene, styrene, 2,3-diphenylindenone, trans-stilbene, triphenylethylene, 1,3,4-triphenylbut-2-ene-1,4-dione, or 3,4diphenylbut-3-en-2-one to the latter reaction promotes the formation of benzyne relative to phenyl radicals, even in the presence of furan. The relevance of these results to the tetracyclone effect is discussed in terms of removal of chain-initiating phenyl radicals by reaction with the unsaturated compounds thus allowing the competing eliminative formation of benzyne from benzenediazonium acetate to become dominant.