1.2- Thiazetidin

Thermolysis of the thiadiazabicyclo[3.1.0]hexene 30, obtained from reaction of an azide with an isothiazole dioxide affords the 1,2-thiazetidine-1,1-dioxide 31, but in poor yield and as part of a three-component mixture <96T7183>. Isocyanates 32 are available in moderate yield <94ZOR1700>. 

Alkylidene sulfenes (75), generally prepared by the dehydrohalogenation of alkylsulfonyl chlorides, add readily to electron-rich multiple bonds. For example, with enamines, the thietane dioxide (e.g., 76) is formed diazoalkanes yield thiirane dioxides (episulfones) and imines (Schiff bases) afford 1,2-thiazetidine 1,1-dioxides. There are available numerous reviews of sulfenes, including cycloaddition reactions.102... 

A stereoselective one-pot synthesis of substituted 1,2-thiazetidine 1,1-dioxides (P-sultams) 55 started from heterocyclic pentafluorophenyl (PFP) sulfonates <06OL5513>. 

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>. 

Thiazetidine 1,1,-dioxides ((3-sultams) 67 were directly synthesised from pentafluorophenyl (PFP) isoxazolidine-4-sulfonates 66 under mild reducing conditions [Mo(CO)6, MeCN, H20, reflux]. The process is stereoselective and goes through N-O bond cleavage followed by intramolecular displacement of the PFP group by the amine <06OL5513>. 

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). 

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. ... 

By treatment of iminosulfuranes with dimethyl acetylenedicarboxylate an unstable, 1,2-thiazetidine (174) was obtained. (Eq. 35b). 

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. 

Ring-opening polymerization of 1,2-thiazetidines, because of their highly strained ring structure, is often investigated for eventual technological applications. Imai et al. have produced a new class of polyamide-polysulfon-amide, using this technique. 4,4-Dimethyl-l,2-thiazetidin-3-one 1,1-dioxide... 

The thiazetidine 163 has been specifically synthesized to give the openring structure 268 after treatment with aniline in acetone at — 78°C. 1,2-Thiazetidines (172) have been treated with Grignard reagents to yield sulfonamide sulfoxides. ... 

Dimethyl-1,2-thiazetidin-l, 1-dioxid6 33% (Rohprod. 74%) Schmp. 35,5-37,5° (Pentan/ Diethylether)... 

Simple saltams, 1,2-thiazetidine 1,1-dioxides, are known to polymerize thermally (73MI51500), although in one case the alkene product was reported to be formed with retention of stereochemistry (Scheme 11) (75BCJ480). 

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

Treatment of 1,2-thiazetidine dioxides with nucleophiles, base (75BCJ480) or methoxide (72LA(763)46) also cleaves the N—S bond (Scheme 34), although at least one account reports carbon-nitrogen scission (70BCJ3543). 

Closures between sulfur and nitrogen are somewhat rare, although it would appear to be a relatively facile approach to the 1,2-thiazetidines (Scheme 59) (75BSF807, 72TL213, 73MI51500, 63JA560). 

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