Dibenzo thiazine

Experimental thermodynamic data have been reported for dibenzo-l,4-thiazino[3,2-/ ][l,4]thiazine 166 <1997MI565> compared to the corresponding oxazinooxazine, replacement of oxygen by sulfur increases ring strain. Crystallographic data show that the nitrogen centres in 166 are /7-periplanar <1994JCM458>. 

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>. 

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

Hori and co-workers accomplished the first synthesis of azathianaphthalene and azathiaphenanthrene in 1979 <79TL3969>. Their approach began with the formation of an olefin from ort/io-nitrobenzaldehyde 43, via a Wittig reaction with an ylide and a subsequent reduction with zinc to afford cis and tram or//io-aminostyryl methyl sulfide 45. The cis-olefin was then treated with NCS, AgC104 and KOH to yield 2-methyl-l-aza-2-thianaphthalene 47 in 41% yield. 9-Methyl-lO-aza-9-thiaphenanthrene 48a and 9-ethyl-10-aza-9-thiaphenanthrene 48b were obtained in a similar fashion in almost quantitative yields, whereas 6-benzyl-6//-dibenzo[c,e][l,2]thiazines 50 were isolated in moderate yields via a 1,2-rearrangement (Scheme 13) <90TL7021>. 

Dibenzo[Z),e ]thiepinones are reductively ring opened at the benzylic C-S bond [194] anthrone and anthraquinone are among the products. The cleavage and ring closure are akin to those observed in the reduction of 2-phenyl-l,3-thiazin-6-ones to 3-hydroxy-pyrroles [195]. 

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. 

---