Pyrido benzothiazine 5,5-dioxides

Treatment of 1-arylsulfonylpipecolinamides 46 with excess EDA gave pyrido[l,2-ft][l,2]benzothiazine 5,5-dioxides 47 in a carbanion-mediated reaction (97SL1079, 98MI2). When the reaction mixture of 46 (R = Me, R = H) was quenched with Mel an ethyl derivative 47 (R = Et, R = H) was obtained. 

Bromo atom of ethyl (3S)-10-bromo-3-methyl-7-oxo-2,3-dihydro-7//-pyrido[l,2,3- fe]-l,4-benzothiazine-6-carboxylate was change for hetaryl groups with tributylstannyl derivatives of heterocycles in the presence of (Ph3P)2Pd(II)Cl2 in boiling toluene (OOMIPIO). 7-Aryl-5-oxo-2,3-dihydro-5//-pyrido[l,2,3- fe]-l,4-benzothiazine-6-carboxylates, 6-carboxamides and their 1,1-dioxide derivatives were prepared from 7-chloro derivatives in the... 

Aryl-5-oxo-2,3-dihydro-5//-pyrido[l,2,3- e]-l,4-benzothiazine-6-carbox-amides and their 1,1-dioxides were prepared from the respective... 

The treatment of benzothiazine 26 with NaOEt in the presence of CuC03 in DMF at 70 °C for 5 h provided tricyclic pyrido[l,2-fc][l,2]ben-zothiazine-5,5-dioxide 22 in 42% yield (08TL5711). 

Mixtures of l-(3-chloropropyl)-l,4-dihydro-2//-[3,l]benzothiazin-2-ones or their 3,3-dioxides and anhydrous AICI3 were stirred at ambient temperature for 30 min, and then at 170-180°C for 1 h, to give 1,5,6,7-tetrahydro-3i/-pyrido[3,2,l- ][3,l]benzothiazin-3-ones and their 2,2-dioxides [88JAP(K)88/170385]. 

Zinnes and co-workers prepared pyrido[l,2-b][l,2]benzothiazines (Scheme 8) 1,2-benzothiazine 182 with isopropyl iodide and potassium carbonate resulted in spontaneous aldol cyclization of the intermediate enol ether 183 to 7,8-dihydro-8-hydroxy-ll-isopropyloxy 8-substituted pyrido[l,2-b][l,2]benzothiazin-10(9//)-one 5,5 dioxide (184). In sulfuric acid, dehydration and ether cleavage of 184 gave the corresponding unsaturated )3-diketone 185. Hydrogenation gave the saturated analogs 186. An attempt to prepare 186 directly by base-catalyzed cyclization of 187 afforded a high yield of 2,3-dihydro-6/f-oxepino [3,2-c][l,2]benzothiazin-5(4H)-one 7,7-dioxide (188) (Eq. 39). 

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