Reactions of acylarylnitrosamines

Abstract

The decomposition of acylarylnitrosamines in benzene and halogenomethanes has been studied. "Benzyne adducts" are formed in yields up to 82% in the decomposition of N-nitrosoacetanilide in the presence of various 2,3,4,5-tetraarylcyclopenta- dienones and anthracenes, and competition reactions using mixtures of arynophiles gave competition constants identical to those from similar reactions using authentic sources of benzyne, W-Nitroso- acetanilide did not, however react with furan to form l,4-dlhydronaphthalene-l,4-endoxide, and the yield of 1,2,3,4-tetraphenylnaphthalene formed in the reaction with 2,3,4,5-tetraphenylcyclopenta- dienone in benzene was gradually reduced from 22% to 1.4% on addition of furan, N-Nitrosoacetanilide has been shown to react with dimethylacetylene- dicarboxylate in benzene to give cis-, and trans- dimethyl diphenylmaleates and 1,2,3,4-tetracarbo- methoxynaphthalene in good yield, in addition to the expected biphenyl. The reaction of benzyne from pentyl nitrite and anthranllic acid, however, gave only 5,6,11,12-tetracarbomethoxydlbenzo [a,ej cyclooctatetraene. These results are discussed, and the suggestion made that the intermediate leading to the formation of "aryne adducts" need not be a true aryne. An arynoid species, the dipolar conjugate base of the aryldlazonium cation, formed by removal of the o-proton, is suggested as a possible alternative. The reactions of acylarylnitrosamines with halogenomethanes have also been studied, and the results compared with those of similar reactions of arylazotriphenylmethanes and aryldlazonium halides and fluoroborates. The participation of diazoniam halides and acetate has been demonstrated in the reactions of N-nitrosoacetanilide, and possible mechanisms involving formation of diazonium halides have been suggested. The decomposition of o-t-butyl-N-nitroso-acetanilide in halogenomethanes led to the formation of the o-, and m-t-butylphenyl halides, in addition to the o-, and m-t-butylphenyl acetates. Participation of 3-t-butylbenzyne was confirmed by the isolation of 5-t-butyl-l,4-dihydronaphthalene-1,4-endoxide when o-t-butyl-N-nitrosoacetanilide was allowed to decompose in bromotrichloromethane in the presence of furan; this was accompanied by a suppression of formation of the m-t-butylphenyl halides and acetate, A reaction scheme is suggested involving participation of diazonium halides and acetate. The reaction of N-nitroso-N-formylanthranilic acid and N-nitroso-N-acetylanthranilic acid with 2,3,4,5-tetraphenylcyclopentadlenone in benzene led to the formation of 1,2,3,4-tetraphenylnaph- thalene, but the principal products in these reactions were 3,1-benzoxazin-4-one and 2-methyl-3,1-benzoxazin-4-one respectively.