N 1 -Acyl-, N 1 -alkoxycarbonyl-, and N 1 -(N,N-dialkylcarbamoyl)guanidines bearing electron-withdrawing cyano or sulfonyl group at the N 3 -position were found to provide corresponding rearranged products, 1,3,4-oxadiazoles, when these guanidines were chlorinated by sodium hypochlorite followed by treating with base. Assignments of obtained compounds were accomplished by means of some reactions such as acid hydrolysis, alkoholysis, and catalytic hydrogenations, and of MS spectra.We previously reported that N 1 -acyl-N 3 -cyanoguanidines reacted with hydroxylamine hydrochloride to afford various type of 1,2,4-oxadiazoles. 1 In this connection, we subsequently investigated the chlorination and cyclization of N 1benzoyl-N 3 -cyanoguanidine in order to obtain 3-cyanoamino-5-phenyl-1,2,4-oxadiazole. However, the product thus obtained was found to be 2-cyanoamino-5-phenyl-1,3,4-oxadiazole. It was also clarified that N 1 -acylguanidines, N 1 -alkoxycarbonylguanidines (N-amidinocarbamates), and N 1 -(N,N-dimethylcarbamoyl)guanidine (1-amidino-3,3dimethylurea) bearing electron-withdrawing cyano or sulfonyl group at the N 3 -position gave corresponding rearranged 1,3,4-oxadiazoles.Fuchigami and Odo first reported in 1974 that treatment of N-benzoyl-N'-chlorobenzamidine with base gave 3,5-diphenyl-1,2,4-oxadiazole. 2 This reaction has been proved to be applicable to N-chloro derivatives of benzoylguanidines (1), 3 alkoxycarbonylguanidines (2), 3 and carbamoylguanidines (3) 4 providing 3-amino-1,2,4-oxadiazoles (4).
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