Oxidation of 1,2‐Thiazoles; A Convenient Approach to 1,2‐Thiazol‐3(2H)‐one 1,1‐Dioxides The 1,2‐thiazoles obtained from 3‐chloroalk‐2‐enals and ammonium thiocyanate (7 → 9, Scheme 1) are easily transformed to 1,2‐thiazol‐3(2H)‐one 1,1‐dioxidcs 10 on treatment with H2O2 in AcOH at 80°. Hydrogenation of 10 in AcOH yields the corresponding saturated 1,2‐thiazolidin‐3‐one 1,1‐dioxides 16 (Scheme 3). Cycloalka[c]‐1,2‐thiazoles 18 are prepared from 2‐[(thiocyanato)methyliden]cycloalkan‐1‐ones and ammonia (Scheme 4). Surprisingly, oxidation of 18a with H2O2 in AcOH yields the tricyclic oxaziridine 19.

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Synthesis of New N‐Aroylisothiazole‐2‐imines and N‐Aroylaminoisothiazolium Salts by Cyclisation of Thiocyanato‐substituted Hydrazones The synthesis of new N‐aroylisothiazole‐2‐imines (4g‐n) as well as the corresponding acceptor‐substituted 2‐amino‐isothiazolium salts (6f‐n) by cyclocondensation of thiocyanatovinylaldehyde hydrazones (3) is reported. The structure of these N‐imines was proved by spectroscopic methods. The alternative cyclization route to 1,2,3‐thiadiazines (8) is not observed. The hydrazones (3a‐e) could not be cyclized to N‐imines, only sulfides (5a‐c) were obtained. The reaction of 2‐thiocyanatomethylen‐cycloheptan‐2‐one (9) with benzhydrazides gave the same ring closure to the salts (10a,b). The structure of the N‐imine 11b has been confirmed unequivocally by X‐ray structure analysis.

Oxidation of 1,2-Thiazoles: A Convenient Approach to 1,2-Thiazol-3(2H)-one 1,1-Dioxides.-With a view to the valuable therapeutical properties of several thiazole 1,1-dioxides the title compounds (IV) are synthesized by oxidation of the corresponding thiazoles (III). The oxidation of the compound (VI) which is isomeric to (IIIe) leads to the sulfonyloxaziridine (VII). -(SCHULZE, B.; KIRSTEN, G.; KIRRBACH, S.; RAHM, A.; HEIMGARTNER, H.; Helv.

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