1.2.3- Oxathiazine 2,2-dioxides, 4-chloro

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. ... 

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... 

The 4-oxo-l,2,3-oxathiazine 2,2-dioxides (418), known to be formed from ketones R COCH2R and FSI (FSI is FSO2NCO), can be chlorinated to afford the 4-chloro-derivatives (419). The attack of nucleophiles upon these latter compounds occurs at the 6-position, giving /3-functionalized acrylonitriles (420) and (421) (20—60%) the cis trans ratio varies from 0 100 to 95 5 (Scheme 164)." °... 

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