A Ring Fission/C-C Bond Cleavage Reaction with an N-Alkyl-N-methyl-3-methylamino-5-phenyl-1,2,4-oxadiazole

The reaction of N-(3,4-dichlorophenethyl)-N-methylamine (1) with 3-chloromethyl-5-phenyl-1,2,4-oxadiazole (2) was investigated. Employment of an equimolar amount of 1 and 2 in the presence of potassium carbonate led to the expected tertiary amine 3 (N-[(3,4-dichlorophenyl)ethyl]-N-methyl-N-[(5-phenyl-1,2,4-oxadiazol-3-yl)methyl]amine), whereas an excess of 1 and prolonged reaction time resulted in ring fission of the oxadiazole system in 3 and finally in the formation of N?-benzoyl-N-[(3,4-dichlorophenyl)ethyl]-N-methylguanidine (4) and N,N?-bis[(3,4-dichlorophenyl)ethyl]-N,N?-dimethylmethanediamine (5). The structures of products 3¿5 were determined by means of 1H and 13C NMR-spectroscopy, mass spectrometry and IR-spectroscopy, for 3 (as picrate) and 4 also X-ray structure analysis was employed. A possible mechanism of the reaction pathway leading to compounds 4 and 5 is proposed.