1.2- Thiazetidine 1-oxides reactions

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 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. 

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 facile cleavage of the S-N (7-bond in the 1,2-thiazetidine A-oxide 54 is part of the driving force in its rearrangement and this feature was exploited in reaction with nucleophiles. Thus, treatment with methanol affords the ring-opened alkyl sulfinate 56 in 86% yield while similar reaction using -butylamine leads to the sulfmamide 57... 

Moreover, the 2-vinyl-l,3-thiazetidine 98a (R1 = R2 = Et) undergoes rearrangement to thiazine sulfone 101 when treated with peracid. A by-product sultine compound 102 was isolated in 6% yield from this reaction. This could be the result of a [2,3]-sigmatropic rearrangement of the sulfone. The reduced 2-vinyl-l,3-thiazetidine 103 is also oxidized with peracid affording the thiazine sulfone 104 but no product corresponding to the sultine was detected (Scheme 30) <1999J(P1)3569>. 

An acidic solution of 2,4-dinitrophenylhydrazine reacts with N-p-chlorophenyl-sulfonyl-3-ethoxy-l,2-thiazetidine 1-oxide to give (80%) the bis-2,4-dinitrophenyl-hydrazone of glyoxal. The adduct of A-sulfinyl-p-chlorophenylsulfonamide with dihydropyran is inert to catalytic hydrogenation and bromination. Treatment of two l,2-thiazetidine-3-one 1-oxides (e.g., 421) with hydriodic acid results in ring-cleavage and loss of sulfur. They are not oxidized to 1,1-dioxides by peracetic acid, ° but m-chloroperbenzoic acid accomplishes this oxidation. The unstable adducts with ketene decompose to amides with loss of hydrogen sulfide and sulfur dioxide or may be trapped by reaction with aromatic amines as shown for thiazetidine 1-oxide 422.An aldol-type condensation has been reported for A -cyclohexyl-1,2 thiazetidine-3-one 1-oxide and p-(A(A"-dimethylamino)benz-aldehyde. " Sulfur monoxide is lost in the flash-vacuum thermolysis of 422a. ... 

The addition of thiobenzophenone to nitrosobenzene to give N-(diphenyl-methylene)benzenamine is said to go via a cyclic intermediate that loses sulfur monoxide to give the product. A similar mechanism is invoked in the reaction of aldehydes with 5,5 -diphenylsulfilimine to give enamines or nitriles (e.g., 587). Oxa-2,3-thiazete-2-oxides are suggested as intermediates in the dehydration of aryl amides to nitriles by thionyl chloride.The reaction of Af-sulfilamines with aldehydes, which previously were suggested to give oxa-2,3-thiazetidine-2-oxides, has been shown to yield acyclic compounds. 

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. 

Four-membered Rings.—Open-chain sulphinate esters are readily prepared but their cyclic analogues are less easily come by. [2 + 2]Cycloadditions involving SO2 are limited to a few specialized examples, and it has been suggested that it is this mode of reaction that leads to the initially formed adduct (274) between SO2 and ketenimines. These compounds are unstable and rearrange to thiazetidine 5-oxides (275) in 90% yield. A versatile approach has been... 

Thiazetidines and Thiazetes.— The reaction of sulphur di-imides with ketens leads ultimately to 1,2-thiazetidine derivatives (1 by way of intermediates (185) and (186). Oxidation of (187) with m-chloroperbenzoic acid leads to the S-oxide (188). The 1,2-thiazetidine intermediate proposed to account... 

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