Cyanogen bromide reaction with, phosgene

Various fused systems, e.g. (494), have been prepared via reactions of compounds of type (492) or (493) with Ci reagents such as phosgene, thiocarbonyl chloride or cyanogen bromide (76T57, 839). 

The pyrazolo[4,3-e][l,2,5]oxadiazin-3-ones (163) are formed by the action of phosgene or ethyl chloroformate on the aminonitrosopyrazoles (162) (Equation (22)). They have been used as intermediates in peptide synthesis <761ES70). A pyrazolo[4,3-e][l,3,4]oxadiazine (165) is formed together with a pyrazolotriazine (166) (Equation (23)) by the reaction of the phenylhydrazone of a pyrazolone (164) with cyanogen bromide <85JCS(P1)1499>. 

The first synthesis of a 1 HA, 2,4-benzothiadiazine 1-oxide and simultaneously of the first cyclic sulfoximine were reported in 1964. 22 1 //-1,2,4-Benzothiadiazines were later prepared123 by reaction of S-(2-aminophenyl)sulfoximine 1 with cyanogen bromide to give 1//-1,2,4-thiadi-azin-3-amine 1-oxide 2a. Compounds 1 also react with phosgene to yield 1//-1,2,4-benzo-thiadiazin-3-amine 1-oxides 2b and c.123 An alternative route to 1 H-, 2,4-benzothiadiazine 1-oxides from sulfoximines and C-synthons has also been reported. 24 128... 

---