1.2- Thiazetidine 1-oxides

Thermolysis of the pentacoordinate 1,2-thiazetidine 1-oxide 56, which was synthesized for the first time and characterized by X-ray crystallographic analysis, gave the corresponding aziridine 57 and a cyclic sulfinate almost quantitatively <06OL4625>. 

N-Sulfinylsulfonimides treated with vinyl ethers give 1,2-thiazetidine 1-oxide (Eq. 35a). Investigation of the stereochemistry of this reaction showed that no isomerization occurs between the forms 172 and 173, which is the rule for the corresponding azetidines. ... 

The relatively rare 1,2-thiazetidine 1-oxides can be oxidized to sulfoxides with MCPBA (Scheme 25) (81TL583). 

V-Sulfonyl-3-alkoxy-1,2-thiazetidine 1-oxides illustrate the sensitivity of the N—S bond towards nucleophiles such as Grignards (Scheme 33) (66CB3903). 

Proton nmr spectroscopy distinguishes between axial and equatorial 5-oxide isomers, for example, 416a and 416b, respectively." The axial proton at C-3 is deshielded by axial S-0. In 1,2-thiazetidin-3-one 1-oxides, the S-oxide absorbs at 1130-1143 cm in the IR linear sulfinylamides absorb at 1025-1050cm . Absorption of the 5-oxide occurs at 1080-1090cm in A-sulfonyl-l,2-thiazetidine 1-oxides." C nmr spectra aided in establishing the structures of 2-substituted-3-keto-4,4-dimethyl-1,2-thiazetidine 1-oxides." "... 

Furthermore, 1,2,-thiazetidine 1-oxides are the products from A -sulphinyl-sulphonamides and dimethylketen 7V-phenylimine, and not 1,2,4-thiadiazetidine 1-oxide, as previously reported... 

Kano, N. Daicho, Y Kawashima, T. A potential intermediate for the aza-Corey-Chaykovsky reaction synthesis, structure, and thermolysis of a pentacoordinate 1,2-thiazetidine 1-oxide. Org. Lett. 2006, 8, 4625. 

The easily prepared thiazetidine. -oxides 38 undergo thermal isomerization by fission of the N-S bond to yield syn and anti isomers of 1,4-thiazine 5-oxides 39 <97SL 167>. 

There are two reports describing the preparation of derivatives of 1,2-thiazetidine-1,1-dioxide. The sulfur atom in L-cystine diethyl ester was oxidized and the corresponding sulfonyl chloride was cyclized with ammonia (Scheme 3) (60CB784). A similar transformation used protected )3-homocysteine as starting material (94LA251). 

The UV spectra of 1,2-thiazetidinone oxides have been recorded by Beeken and Korte. Measured in cyclohexane or chloroform, the N-substituted cyclohexyl- (35), phenyl-, and aryl-substituted 4,4-bisphenyl-l,2-thiazetidin-3-one 1,1-oxides showed an average absorption band at = 240 nm... 

A novel synthesis in which diazoketones are thermolyzed with JV-sul-finylamines leads to cyclic S-oxides such as 3,4-dihydro-1,2,3-oxathiazine and 1,2-oxazetidine derivatives. A similar synthesis utilizing diazodiketones yields, via a 4 -f 2 cycloaddition, oxathiazines (165) and, via 2 -F 2 cycliza-tion, thiazetidines (166). When sulfonyldiazoketones were used, thiazetidines 167 were the only isolated products (Eq. 33). 

The most studied reactions of the thiazetidines are the thermolytic decomposition and conversion reactions. 1,2-Thiazetidines are more unstable than the 1,3-thiazetidines because of the lone-pair-lone-pair repulsion of the N—S bond. Oxidation of the sulfur atom or appropriate substitution on the nitrogen atom have a stabilizing effect on the ring structure. 

Reduction of 155 by Raney nickel produced the ring-opened structure 269. Oxidation of the same compound with m-chloroperbenzoic acid resulted in the formation of the thiazetidine 1-oxide 163. 

Four-membered ring adducts from 2n + 2n cycloaddition of keten-imines to sulfur dioxide. Isolation of l,2-thiazetidin-3-one 1-oxides. jS-Sultames. Simple method for synthesis of substituted 1,2-thia-zetidin 1,1-dioxide. ... 

Peroxide oxidation of 2-imino-l,3-thiazetidine does not lead to simple sulfur oxidation. Oxidative cleavage and ring closure result in 3-oxo-l,2,4-thiadiazolidine 1-oxide formation (Scheme 27) (76AG(E)103). 

The intermediacy of a 4-imino- 1,2-oxathietane 2-oxide from the addition of sulfur dioxide to ketenimines was inferred from the trapping with methanol. The final isolated product in absence of methanol, l,2-thiazetidin-3-one 1-oxide, was established by X-ray (Scheme 42) (81CC350). 

Saturated rings such as 1,2-thiazetidines 5, 1,2-thiazetidine A-oxides 6, 1,2-thiazetidine 1,1 -dioxides, commonly named /3-sultams 7 and 1,3-thiazetidines 8 ... 

The diagonalization reaction of 1,2-thiazetidine A-oxide 10 was theoretically studied at the B3LYP/6-31G level as a concerted bond formation between the diagonal saturated atoms to produce thiirane with the extrusion of HNO (Equation 1). The activation energy was calculated to be 153 kj mol-1, suggesting that the reaction could be observed experimentally <1999TL8893>. 

The protons in the 1,2-thiazetidine T-oxide ring 22 appear as a pair of doublets as expected for fit-coupling in a four-membered ring, but significantly they are not coupled to the vicinal bridgehead protons of the norbornene component thereby confirming the fuco-fusion <1997SL167>. 

Characteristic 13C NMR chemical shifts of the l,2-thiazetidine-3-one A-oxide 45 have been described <1998JFC9>. 

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