Aliphatic diazo compounds. IX. The base-induced dimerization of α-diazo ketones

Treatment of 2-diazoacetophenone (1) with potassium t-butoxide in t-butyl alcohol gives a colorless dimer, which is shown to be 5-benzoyl-2-phenacyltetrazole (4) by its independent synthesis by phenacylation of 5-benzoyltetrazole. The latter reaction also gives 5-benzoyl-1-phenacyltetrazole (3), which is distinguished from 4 by its reduction to di(2-hydroxy-2-phenylethyl)amine and by its cyclization on treatment with ammonium acetate. The assignment of the structure of the colorless dimer of 1 permits the postulation of related pathways for its formation and that of the red-brown dimer obtained on treatment of 1 with potassium hydroxide in dimethyl sulfoxide. 2-Phenacyltetrazole (22) and benzoic acid are formed in addition to 4 on treatment of 1 with potassium t-butoxide in t-butyl alcohol; these are considered to arise via cleavage of 4, since prolonged treatment of 4 and 3 with potassium t-butoxide in t-butyl alcohol gives 22 and 1-phenacyltetrazole (24), respectively. Compounds 22 and 24 have been prepared independently by phenacylation of tetrazole.