Dibenzo thiazine 1,1-dioxides

Dibenzo[l,2]dithiins 54 are prepared by oxidation of appropriate dithiols 53 and related starting materials (e.g., Scheme 27). Dibenzo[l,2]thiazine dioxide 56 is obtained by thermolysis of the azide 55 (Scheme 28) <1969JA1219>. 

Normally, decompositions of azides in hydrogen-rich solvents are avoided in order to minimize the formation of products based on triplet nitrene. Surprising, therefore, is the report that 6i/-dibenzo[c ,e][l,2]thiazine 5,5-dioxide (335) is obtained in optimum yield (80.6%) from the thermolysis of biphenyl-2-sulphonyl azide in cyclohexane at 120 Decomposition of o-(2-thienyl)benzenesul-phonyl azide under similar conditions furnishes the thieno[3,2-c]benzo-l,2-thiazine dioxide (336), in practicable yield (61%). Whereas, in POCla-pyridine... 

H-(Dibenzo-l,2-thiazin) 8-Brom- -5,5-dioxid E16c, 285 (R — S02 — N3/intra)... 

Abramovitch and co-workers,122 investigating the chemistry of aryl-nitrenes and sulfonylnitrenes, thermolyzed biarylsulfonyl azides (136) which at 120°C produced 6H-dibenzo[c,e] [ 1,2]thiazine 5,5-dioxide (138) (80%) via the proposed intermediate 137 (Eq. 34). N-Alkylation of 138 with... 

J-dimethylaminoethyl chloride gave iV-(2-dimethylaminoethyl)-6//-dibenzo-[c,e][l,2]thiazine 5,5-dioxide (139). Ring-substituted derivatives of 138 have also been prepared. 

Oxidation of 142c with lead tetraacetate gave 9H-9-oxodibenzo[c,e][l,2]-thiazine 5,5-dioxide (143). The redox potentials of some 9-substituted dibenzo[c,e] [ 1,2]thiazine 5,5-dioxides (142) have been determined.123... 

There is one interesting example of this type of bond formation in which the bis-sulfonamide (158) can be cyclized with bis(triphenyIphosphine)palladium(II) chloride and sodium acetate to give the dibenzo[c,e][l,2]thiazine 5,5-dioxide (159). It is noteworthy that the monosulfonamide (160) is recovered unchanged under the same reaction conditions (Equation (2)) <84T1919>. 

DIBENZOTHIAZINE or DIBENZO-l,4-THIAZINE (92-84-2) Combustible solid. Mixture with acids or acid fumes causes decomposition and formation of sulfur dioxide and nitrogen oxides. Incompatible with aldehydes, cellulose nitrate (of high surface area), organic anhydrides, isocyanates, nitrates. 

Oxidation of 142c with lead tetraacetate gave 9//-9-oxodibenzo[c,c][l,2]-thiazine 5,5-dioxide (143). The redox potentials of some 9-substituted dibenzo[c,e][l,2]thiazine 5,5-dioxides (142) have been determined. Kaufmann and Zobel first prepared 2,3-dihydro-3-oxonaphtho-[l,8-d,e][l,2]thiazine 1,1-dioxide (146). More recently, this was prepared by Lombardino by an abbreviated process involving lithiation of 144 and treatment with carbon dioxide (Eq. 35). Cyclization of 145 with poly-phosphoric acid simultaneously removed the fcrt-butyl group to produce compound 146 directly. 

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