Pyrido thiadiazine 2,2-dioxides

The single crystal X-ray structure of 3-methyl-4//-pyrido[2,3- ] l>2,4-thiadiazine 1,1,-dioxide 13 was compared to that of diazoxide 14 in order to determine the predominant tautomeric form and it was found that both these thiadiazine-dioxides exist in the AH tautomeric form in the solid state <1995AXG2064>. 

Pyrido[2,3-c]-1,2,6-thiadiazine 2,2-dioxides may be glycosylated under standard conditions to yield glycosides of potential biological interest. Thus, the pyrido-l,2,6-thiadiazine dioxide (51a) yielded nucleosides (170) and (171) <90MI 717-01). 

Selective bromination of pyrido[2,3-c][l,2-6]thiadiazine 2,2-dioxides (206) gave 6-bromo products in 71-85% yields (91SC827). 

Synthesis and structural studies of new 3-alkylamino-pyrido[43-e][l,2,4]thiadiazine 1,1-dioxides have been reported <99T5419>. 

Oxidation of pyrido[23-c][l,2,4]thiadiazines 94 with sodium hypochlorite and, separately, iR-chloroperbenzoic add affords the 1,1-dioxide derivatives 95 and the 5-oxide derivatives 97, respectively. Oxidation of 1,1-dioxide derivatives yields the novel 1,13-trioxides 96 <98T13645>. 

The reduction of 3-(4-bromobenzamidoaminomethyl)-477-pyrido[4,3-< ]-l,2,4-thiadiazine 1,1-dioxide 34 with sodium borohydride in aqueous sodium hydroxide gave the 2,3-dihydro derivative 35 (Equation 3) <1997BSB781>. 

Oxidation of the pyrido[2,3-e]-l,3,4-thiadiazine (52) to the corresponding dioxide (53) was achieved using H202 in AcOH in 61% yield <80JOC3677>. 

Pyrido[4,3-e -1,2,4-thiadiazines 2//,3//,4//-Pyrido[4,3-e]-l,2,4-thiadiazinone 1,1-dioxide (167) was converted into the series of compounds (168a-j), which are inhibitors of insulin release, via the sequence of reactions shown in ... 

Diaminothiadiazine dioxide (342) reacts with 1,3-dicarbonyl compounds to deliver pyrido[2,3-c]-l,2,6-thiadiazines, for example (51b) <86CS607>. The pyridothiadiazine 2,2-dioxides (21a,b) and (22a,b) were prepared by reaction of 3-substituted 5-amino-1,2,6-thiadiazine 1,1 -dioxides (343) or (344) with the corresponding /J-keto ester <88AQ89>. 

A series of 3-(alkylamino)-4H-pyrido[4,3-e]-1,2,4-thiadiazine 1,1 -dioxides (168a-j) that are related to diazoxide (396) (a compound which induces hyperglycemia in vivo through decreased insulin secretion and is a potent pancreatic KATP channel opener) and pinacidil (397) were prepared and tested as inhibitors of insulin release from rat pancreatic islets. Of the compounds tested, BPDZ 44 (168g) was chosen for further study as a potential probe for KATP channels. The compounds tested were the most powerful inhibitors of insulin release reported at that time <93JMC32li>. 

A number of 1 /7-pyrido[2,3-c]-l,2,6-thiadiazin-4(3/7)-one 2,2-dioxides and 1 //-pyrido[4,3-c]-1,2,6-thiadiazin-4(3//)-one 2,2-dioxides, for example (403), display herbicidal properties <75USP392064i, 77USP4014888). Four 3-arylpyrido[3,4-e]-1,2,4-triazines (404a-c) and (252) have been studied as germination inhibitors <84Mi 717-03). 

Disubstituted 2-thioxo-pyrido[2,3-d]pyrimidinones condensed with aldehydes in the presence of chloroacetic acid to yield thiazolo[2,3-a]pyrido[2,3-. One-pot alkoxylation at the 7-position of 6-arylpyrazino[2,3-c][l,2,6]thiadiazine 2,2-dioxides with NBS or NCS in the appropriate alcohol has been studied <02EJ02109>. 

Diamino-4//-1,2,6-thiadiazine 1,1 -dioxide (185) undergoes base-catalysed condensations with -diketones to yield 4-aminopyrido[2,3-c][l,2,6]thiadiazine 2,2-dioxides (186) <86CS607>, and Con-rad-Limpach type cyclization with -keto esters to yield 4-amino-l/7-pyrido[2,3-c][l,2,6]thiadiazin-5(8/f) Oite 2,2-dioxides (187) (Scheme 19) <88AQ89>. 

---