The title reactions yield labile 4,5dihydro-l,3-oxazole-4-spiro-2'-thiiranes 4 which isomerize in solution to the thietan34mines 5. This isomeriiation also occurs when the spiro compounds are heated to their melting points, but here the desulfurized products 8 and 9 are also formed in some cases. These are also the products obtained by SO2 extrusion of the sulfones 10 derived from 5.lsothiocyanates possess two reactive double bonds (C = N and C = S ) that are capable of reacting with 1,3-dipoles, and, indeed, the two cycloadducts are obtained with nitrile imines and azomethine ylides. Nitrones and azomethine imines give only C = N adducts, whereas diazoalkanes, azides, nitrile ylides and nitrile oxides produce C = S adducts.' For instance, the Pechmann synthesis of 1,2,3-thiadiazoles 1 is based on the reactions of diazomethane and monosubstituted diazoalkanes with isothiocyanates.2 Disubstituted diazoalkanes do not react with alkyl and aryl isothiocyanates, but the introduction of strong electronwithdrawing groups adjacent to the isothiocyanate function enhances their reactivity and makes some reactions possible. Thus, diphenyldiazomethane combines with arylsulfonyl isothiocyanates to give thiiranimines 2 after loss of nitr~gen.~ Acyl isothiocyanates also react with diphenyldiazomethane, and our investigations of these reactions have discovered an unusual reaction pattern which is the subject of this present paper.4The acyl isothiocyanates 3a-e reacted with two equivalents of diphenyldiazomethane in diethyl ether at room temperature to yield the spiro compounds 4a-e which precipitated from the concentrated solutions. These compounds proved to be unstable and isomerized into the thietan3imines 5a-e upon warming in chloroform or dichloromethane, or simply when the NMR tubes (CDC13 solutions) were allowed to stand for a prolonged time at room temperature. The structures of the products were elucidated by 'Hand 13C NMR, IR and mass spectral analyses (see Experimental). Thus, two equivalents of diphenyidiazomethane were consumed in all cases, even when the reactions were carried out with equimolar amounts of reagents.

The kinetics of the thermal decomposition of several sulfonyl substituted thiatriazolinimines 1a‐g were investigated in different solvents both in the presence and in the absence of trapping reagents. The first‐order rate constants observed in all cases, are dependent on the inductive effect of the sulfonyl substituent (R), as well as on solvent polarity, but independent on the nature and concentration of the co‐reagent. These results, and the low activation energy, are rationalized by assuming an anchimeric assistance of the sulfonyl group during thermolysis. This would give the intermediate 7, which collapses to the thiaziridinimine 2 before being trapped by the co‐reagent.

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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Reactions of Trichloroacetyl Isothiocyanate with Organic Azides. -13C NMR spectroscopic investigations of the title reactions in chloroform and acetone reveal the formation of 1,2,4-oxathiazolidines, which cannot be isolated. They decompose via carbodiimide intermediates into the products (III). Some trapping experiments with ( IV) and (VI) yield the compounds (V) and (VII), respectively. Reaction mechanisms are presented. -(L'ABBE, G.; BOSMAN, J.; TOPPET, S.; J. Heterocycl. Chem. 29 (1992) 1, 17-23; Dep. Chem., Univ. Leuven, 3001 Leuven, Belg.; EN)