Synthesis of pyrimido[5,4,-b]1,3,4 thiadiazine is limited to only one patent literature of A. J. Eliot1. Recently we exhibited a new approach for the addition of 1, 3, 4 thiadiazine to quinoxaline moiety2. Now we have extended this strategy as an efficient and a general procedure for the synthesis of pyrimido[5,4-b][1,3,4] thiadiazines. Hence a group of alkyl- 2-phenylhydrazinecarbodithioates 2 were reacted with newly synthesized3 5- bromo- 2,4- dichloro -6- methylpyrimidine 1. The structural assignments of these compounds are based on the spectral and microanalytical data.

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