The fragmentation patterns of thiazolotriazoles are in agreement with the individual character of each heterocycle but there are also peaks arising both from their combined influence and from the nature of the substituents in positions 5 and 6.In a previous paper we have discussed the preparation of some thiazolo[3,2-b]-1,2,4-triazoles from 3-phenyl-5-(R-thio)-1,2,4-triazoles.' As no data concerning the fragmentation of these compounds upon electron impact have been published so far, in this paper we report their behaviour in comparison with that of 1,2,4-triazole itself ,233 some substituted triazole derivatives3-'' and some triazole derivatives fused with other heter~cycles."-'~ The mass spectra of the compounds studied in this paper are listed in Table 1.The mass spectrum of 3-phenyl-5-(acetylthio)-1,2,4-triazole is dominated by the [M -421" (McLafferty rearrangement) and mlz43 peaks (Scheme 1). The behaviour of the ion at rnlz 177 is analogous to that of compound 1 (Table 1). It should be noted that out of the whole series of derivatives, only compounds 1 and 2 yielded a peak at mlz 119, corresponding to the t h i~n e .~-~ The [M-42]+' and mlz 43 peaks also predominate in the mass spectrum of the S-acetonyl derivative 4. The ion at mlz 191 arising from rearrangement has similar fragmentation behaviour to compound 3 and other 5-S-methyltriazole~~~'~ with the loss of SH., Ha and HCS.. A weak peak corresponding to the loss of water from the molecular ion is also observed (the 'ortho effect'). The other fragmentation pathways are similar to those of compound 1.For compound 5, the abundance of the ion at mlz 191 occurring from the loss of chloroketene is much smaller than the abundance of the ion at mlz 190 (base peak), corresponding to the a-cleavage.In view of the fact that by the cyclization of compounds 4 and 5, two isomers fused on the b or c side respectively of triazole could be formed, we thought that the fragmentation upon electron impact could give information on the condensation pattern. By analogy with the triazolopyridines and triazolopyrazines studied by Potts et a1.,127'3 which give N, loss in the case of 1,2,4-triazole derivatives fused on the c side while the N, loss does not occur at the same compounds fused on the b side, we consider that the absence of N, loss in our compounds is evidence for b side fusion.As far as the fragmentation of these compounds is concerned certain characteristic ions for both phenyltriazole and 4-substituted thiazolic derivatives'"-'' occur. Independent of the nature of substituents in positions 5 and 6, all derivatives give a peak of medium intensity at m/z 144 (identified by high resolution) (Scheme 2). The cleavage of the 4 and 7 bonds, with charge retention by the sulphur-containing portion, results in the appearance of the thiirene ion radical, which as with some 4-substituted thiazolic derivatives, is of strong intensity only in the case of compound 9.15,16,1' Beside these fragmentations, there are also ruptures caused by the nature of the substituent at C-5, rup...
