Thietan-3-ones

A few special syntheses of thiirane derivatives from four-membered sulfur heterocycles are known. Methylenethiiranes are derived by thermolysis of the tosylhydrazones of thietan-3-ones (Scheme 143) (81TL4815), and 2,2,3,3-tetrakis(trifluoromethyl)thiirane is obtained by thermolysis of 2,2,4,4-tetrakis(trifluoromethyl)-l,3-dithietane 1,1-dioxide with loss of sulfur dioxide. 2,2,3,3-Tetrakis(trifluoromethyl)thiirane 1,1-dioxide is obtained in low yield by heating a mixture of 3,3-bis(trifluoromethyl)-l,2,4-oxadithietane 2,2,4,4-tetroxide and bis(trifluoromethyl)ketene. The mono-episulfide of norbornadiene is obtained from thietane derivative (65 Scheme 144) (73JOC649). 

The reaction of thietan-3-one 46 with 1,2,4,5-tetrazines 47 gave 4i/-pyrazolo[5,l-c]thiazines 48 via a rare anti-Michael addition <06TL7893>. 

Several isothiochroman-4-ones rearrange photochemically to thio-chroman-3-ones (61) via the intermediate spiro-thietan-3-one (62) [Eq. (27)].248,249 The ylid (63) is transformed into 1-indanone250 photochemically. 

Thietan-3-one, 2-isopropylidene-4,4-dimethyl-UV, 7, 418 (80JOC4804) lA4- ITiietan-2-one 1-oxide IR, 7, 420 (70JOC584)... 

A variety of examples of photochemically induced elimination of sulfur dioxide from sulfur heterocycles have been reported, with particular attention to cyclic sulfones. Thietan-3-one 1,1-dioxide (525), however, undergoes fragmentation on irradiation in acetonitrile to ketene (526) and to the sulfene (527), the latter identified by infrared spectroscopy and as the methanol... 

The reaction of 2-(diphenylmethylene)thietan-3-one with 1,2,4,5-tetrazines in KOH-MeOH-THF gives 4//-pyrazolo[5,l-c]thiazines. This novel condensation reaction proceeds via the intermediacy of an 8-(diphenylmethylene)-2//-l,4,5-thiadiazocin-7(8H)-one, which undergoes a multi-step rearrangement including a rare anti-Michael addition.30... 

Allene episulfide and butatriene 2-episulfide are formed by thermolysis of the lithium tosyl-hydrazone of thietan-3-ones (Scheme 80) <76JA708l, 81TL4815). 

Chemistry of azetidin-3-ones, oxetan-3-ones, and thietan-3-ones 02CRV29. Formation of four-membered heterocycles through electrophilic heteroatom cyclization 02EJ03099. 

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