SYNTHESIS AND MASS SPECTRA OF 2,3-DIHYDRO-IH-I,5-BENZODIAZEPINE-2-THIONES

l-Methyl-4-phenyl-2,3-dihydro-iH-l,5-benzodiazepin-2-ones Va-c were isolated in the reaction of diazepines IVa-d with methyl iodide, i.e., alkylation takes place at the N(l ) atom. The IR spectra of these compounds do not contain bands of stretching vibrations of free and associated NH groups; signals of a methyl group appear in the PMR spectra. Compounds V readily undergo thionylation to give l-methyl-4-phenyl-2,3-dihydro-iH-l,5- benzodiazepine-2-thiones IIa-c. The alkylation of diazepinethiones I with dimethyl sulfate in methanol or with methyl iodide in benzene in the presence of an interphase-transfer cata- lyst does not take place at the N(I ) atom but rather at the sulfur atom, and 2-methylmercapto derivatives III are formed. Compound IIIa has been previously described (2). The UV spectra of I and II are similar to one another and differ from the absorption spectra of 2-methylmercapto derivatives III with respect to the hypsochromic shift of the short-wave absorption band.