1.4.3- Oxathiazine 4,4-dioxides, reaction

Alkynes react as a two-carbon unit with CSI to give 1,2,3-oxathiazine dioxides. The reaction involves initial addition of CSI to form a four-membered ring which then ring opens and rearranges as shown in Scheme 18 (72JOC196). 

Little is known about the behavior of many of these compounds under halogenation conditions [84MI15 90AHC(47)1], Most reactions involve nucleophilic introduction of a halogen atom. Thus, the standard conversion of an oxo or hydroxy group into chloro is common. Heating with phosphorus pentachloride transformed l,2,3-oxathiazin-4(3//)-one 2,2-dioxides into the 4-chloro derivatives [80AG(E)131]. 

A C-C double bond was also formed on reaction of dicydopropylacetylene with chlorosulfonyl isocyanate. Conceivably a [2-1-2] cycloaddition took place to give an unstable product that rearranged to 6-chloro-4,5-dicyclopropyl-l,2,3-oxathiazine 2,2-dioxide in 96 /o yield. ... 

Apart from oxidative transformations of some systems into the 5-oxides or 5,5-dioxides and some hydrolysis or degradation reactions, little is known about the reactivity of most of the different oxathiazines. Therefore, there is no partition into synthesis and transformation sections in the discussion of these ring systems. 

The reaction of 1,4,2-oxathiazines 8a,b with 3-chloroperoxybenzoic acid yields the 4-oxides 14a,b or the 4,4-dioxides 15a,b depending on the molecular proportions of the reactants.48... 

Substituted 2-dialkylamino-l,4,3-oxathiazine 4,4-dioxides 18 can be obtained from acetone-1,3-disulfonyl chlorides and dialkylcyanamides in good yields.62 Substitution reactions allow for variation in the ligand X. Heating the intermediate at 80 °C causes elimination of sulfur dioxide to give 18 (X = Cl) in 54-86% yield.62... 

Oxathiazine 4,4-dioxides 19 are formed in the reaction of arylethynylsulfonamides with isocyanates and potassium carbonate.63... 

Oxathiazine 4,4-dioxides (36a, b) are prepared in good yield from 1,3-bis(chloro-sulfonyl)acetone (143) and dialkylcyanamides (144) <88S52l>. The reaction goes through the N-sulfonylcarbimidoyl chloride (145) which cyclizes with loss of HCl to form the sulfonyl chloride... 

Cyclocondensation and other reactions with S03 and adducts of S03 has led to the synthesis of a wide range of compounds including l,2,3-oxathiazin-4-one dioxides (142)189, cyclic sulphur trioxide adducts (143)190, piperidinone (144)191 and iV-isopropyl-iV -2-carbomethoxy sulphamide (145)192. 

Reaction of acetylsulphamoyl chloride with sodium hydride was used to generate the N-sulphonylurethane 293 which, when reacted with the ynamine 294, yielded the 6-(dimethylamino)-2-methoxy-5-phenyl-1,4,3-oxathiazine-4,4-dioxide 295300 (equation 93). 

Addition to aromatic ketones An extensive study of the reaction of CSI with aromatic ketones (1) presents evidence that the first step is formation of a 3-keto carboxamide (2), which can react with another molecule of CSI to form a malonamide (3). Generally, however, (2) reacts with CSI to form, after reductive hydrolysis with sodium sulfite, either an oxathiazine 2,2-dioxide (4) and/or an oxazinedione (5). The ratio of (4) to (5) depends on the keto-enol equilibrium of the intermediate (2) and on the reaction conditions. 

In the reaction of acetylenes with halosulfonyl isocyanates (X = F,C1) 6-halo-l,2,3-oxathiazine-2,2-dioxides 57 are obtained. Rearrangement of the initial [2+2] cycloadduct to an imino ketene, followed by cyclization, accounts for the formation of 57. With two... 

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