Benzoxathiazine dioxides

Scheme 6.12) [158 160]. They also demonstrated that benzoxathiazine dioxides could be used to synthesize chiral amino alcohols by LiAlH4 reduction of the sulfamidate formed from hydrogenation. 

Benzoxathiazine dioxides 21 result from the cyclization of (2-hydroxyaryl)sulfonamides, which can be carried out using various reagents, e.g. ortho esters or phenylacetyl chloride.64... 

The benzoxathiazine dioxide 19 has recently been reported, for the first time, to catalyse the epoxidation and C-H hydroxylation of a range of substrates (Scheme 1.23) [61]. 

Basicities 565-567 Basis orbitals 2-5 Benzisothiazolinone dioxides 163 Benzofurans 638 Benzoic acids, pKa values of 586 Benzoxathiazine 2-oxides 71 Benzyne intermediates 306 Beta scales 559... 

Oxathiazinone dioxides have been used for the synthesis of a new type of heterocyclic N — F reagent 4, which are obtained by direct fluorination of salts of the oxathiazinone dioxide derivatives 3 with a mixture of 5% fluorine in nitrogen at low temperatures.136 137 Isolation of the pure compound 4a or 4b is generally rather difficult and the material is not stable in air at room temperature. In contrast, 3-fluoro-l,2,3-benzoxathiazin-4(3//)-one 2,2-dioxide (4c) is a colorless, thermally stable solid with a melting point of 61 "C.137... 

Fluoro-l,2,3-benzoxathiazin-4(3//)-one 2,2-dioxide (4c) can be used for the electrophilic fluorination of both neutral and anionic nucleophiles of a variety of organic compounds under very mild conditions (Table 13).137... 

Benzoxathiazine 2,2-dioxides 9 do not possess aromatic or antiaromatic character and are therefore only discussed briefly. Compounds 9 can be synthesized by cyclization of 2-hydroxy-aryl ketones with sulfamide or chlorosulfonyl isocyanate.28-30... 

Apart from dihydro derivatives 240 there are 2,1,4-benzoxathiazine 1,1-dioxides 3, which are obtained from thermolysis of aryl 2-azidosulfonylphenyl ketones41 or from thermal cycliza-tion of pyridinium salts of 2-acetylaminobenzenesulfonic acids with phosphorus pentachlo-ride.42 7-Methyl-2,l,4-benzoxathiazin-3(4//)-one 1,1-dioxide (4) has been obtained by sulfona-tion of 4-tolyl isocyanate.11... 

Phenyl-4,l,2-benzoxathiazine 1,1-dioxide (24) can be obtained from thermal decomposition of the diazonium salt 23, which in turn is accessible from the sulfonamide 22.65... 

A soln. of methyl 2-(sulfamoyloxy)benzoate in 4 3 ethanol/0.02 M phosphate buffer (pH 7.4) added to a freshly prepared suspension of rat liver microsomes, and incubated under aerobic conditions at 22-5° for 20 h with gentle shaking - 4-oxo-3,4-dihydro-l,2,3-benzoxathiazine 2,2-dioxide. Y 74%. F.e. and 2fM,3-benzoxazin-2-ones from o-carbamyloxyketones s. A. Kamal et al., J. Org. Chem. 53,4112-4 (1988). 

The Diels-Alder cycloaddition of chiral cyclic 2-amidodienes, derived from chiral a-allyl allenamides, with enones yielded optically enriched [2.2.2]bicyclic adducts with dr up to >95 5. In the presence of HOMO-raised trienamines, e-deficient l-aza-l,3-butadienes containing 1,2-benzoisothiazole-1,1-dioxide or 1,2,3-benzoxathiazine-2,2-dioxide react as dienophiles in normal-electron-demand Diels-Alder reactions rather than the corresponding inverse-electron-demand versions. The Fe(III)-catalysed benzannulation of 2-(2-oxyethyl)-benzaldehydes with alkynes produced naphthalene derivatives in high yields (99%) under mild reaction conditions. ... 

A new method has been reported for the preparation of 1,2,3-benzoxathiazine-2,2-dioxides (314), Finally, 1,2,5-benzoxathiazepines (315) have been prepared through a novel rearrangement of the unstable adducts of sulphene with A -benzylidene-2-hydroxyanilides. The compound obtained was identical with that produced unambiguously by an alternative route. 

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