Synthesis of 1-2,1-benzothiazine 2,2-dioxide sulfostyril derivatives

An improved synthesis of li/-2,l-benzothiazine 4(3i/)-one 2,2-dioxide 33 that results in a relatively high overall yield was developed by Lombardino s group 710PP33 72JHC315 . This general method offered an easier entry into the 2,1-benzothiazine 2,2-dioxide heterocyclic system 67JHC403 . Treatment of methyl A-benzyl-A-methylsulfonylanthranilate 35 with sodium hydride led to 1-benzyl-4-oxo-l//-2,l-benzothiazine-4(3/7)-one 2,2-dioxide 36 in 68% yield. Reduction of 36 gave 4-oxo-17/-2,1 - 

Rossi and co-workers 66AC(R)728 also showed that ortho-acyl methanesulfanilides 41 carrying an electron-withdrawing group at the a position of the sulfonyl group can readily 

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