Thieno -l,2-thiazines

Pfister and co-workers129 recently prepared derivatives of the third possible thieno-l,2-thiazin-4-one. Methyl 2-chlorosulfonylthiophene-3-car-boxylate (161) with glycine methyl ester gave intermediate 162, which afforded 4- hydroxy- 3- methoxycarbonyl - 2 H - thieno [3,2-e] -1,2- thiazine 1,1 -dioxide (163) upon heating with base. Alkylation of 163 with methyl iodide/sodium hydride gave 164 which afforded a thieno-1,2-thiazine analog (165) of piroxicam (29) when heated with 2-aminopyridine (Scheme 6). 

Pfister and co-workers130 have also prepared the three isomeric thieno-l,2-thiazin-3-one ring systems. The acid chloride 171 of 3-(2-N-methylsulfamoyl)thiopheneacetic acid (170) with sodium bicarbonate gave 3,4-dihydro-2-methyl-3-oxo-2//-thieno[3,2-e]-l,2-thiazine 1,1-dioxide (172) (Eq. 37). 

Pfister and co-workers recently prepared derivatives of the third possible thieno-l,2-thiazin-4-one. Methyl 2-chlorosulfonylthiophene-3-car-boxylate (161) with glycine methyl ester gave intermediate 162, which afforded... 

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