2-Azetidinethiones

The [2+2] cycloaddition reaction of isothiocyanates with carbodiimides generally proceeds across the C=S bond of the isothiocyanate to give thiazetidine derivatives 218. However, in the reaction of methyl isothiocyanate with N-(4-dimethylaminophenyl)-N -methylcarbodiimide a mixture of the thiazetidine derivative 218 and the isomeric iminodi-azetidinethione derivative 219 is obtained. The structure of 219 was confirmed by X-ray crystallography. ... 

Azetidiniminium salts have also been converted - into azeddine-thiones, -imines or -hydrazones (Scheme 36). Yields of imine derivatives are high when the azetidiniminium salts bear no hydrogen atom at C-3. Otherwise the reaction is best effected by first forming the corresponding 2-azetidinethione which is further treated with an amine in the presence of mercury(II) acetate (Scheme 37),... 

Azetidinethiones are formed - in the reaction of imines with dialkylthioketenes (equation 81). These also react across the C =N bond of electrophilic isocyanates (equation 82). ... 

A notable exception is found in the reaction of iminium salt (35) derived from N-phthaloylglycinamide with imines (Scheme 40). The presence of the phthalimido substituent requires a modification of the pro-cedure converting the adduct (36) into the 3 lactam (38). While basic hydrolysis destroys compound (36), treatment with sodium hydrogensulfide smoothly gives the azetidinethione (37) which is readily oxidized to the corresponding 3-lactam (38) with modest overall chemical yield but high enantiomeric purity. 

The photoreactions of thiones continue to attract attention. Matrix isolation studies of the phototautomerism of 2 (Iff)-pyridine-thione, 4(3H)-pyrimidinethione and 3(2H)-pyridazinethione have been described. Photoreactions involving intramolecular hydrogen abstraction by a thione have also been reported irradiation of the N,W-dialkyl-a,j3-unsaturated thioaraides (144) in benzene, for example, gave the azetidinethiones (145) in good... 

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