Abstract
N-Mono- and N,N-di-substituted-N'-hydroxyguanidines, a new class of intermediates, have been cyclized into new 3-mono- and 3-disubstituted-1,2,4-oxa- and -thia-diazoles either directly from the hydroxy, guanidines themselves; or indirectly by a procedure which has been developed for conversion of some substituted cyanamides into 1,2,4- oxadiazoles without isolating the substituted hydroxyguanidine intermediates. Many new N,N-di-substituted-N'-hydroxyguanidines were prepared and identified. In an improved procedure, the free hydroxylamine could be made to crystallize from absolute ethyl alcohol in 85 % yield. Some new 5-chloro-3-dialkylamino-1,2,4-thiadiazoles have been prepared by cyclization of N,N-dialkylguanidine hydrobromides using trichloromethanesulphenyl chloride. Replacement of the chlorine atom in the 5-position of the thiadiazole ring by other groups e.g. -OCH[3], HH[2], morpholino, piperidino, and some others was accomplished in about quantitative yields. A general procedure has been developed to prepare the N,N-disubstituted guanidine hydrobromides in quantitative yields. 5-Chloro-3-di-n-butylamino-1,2,4-thiadiazole has been tested for biological activity and it was found active as a nematocide, controlling root-knot completely at 125 p.p.m. The 3-di-n-propyl analogue has been submitted to be tested for the same activity. A few of the oxadiazoles and some of the intermediates have been tested and found to have a slight antibiotic activity. The behaviour of the new 1,2,4-oxa- and -thia-diazoles in the Diels-Alder reaction was investigated. The IR and PMR spectra of all the new compounds are discussed in some detail; the UV and the MS spectra of some of these compounds are briefly discussed.