Two-step conversion of 3,4,4,5-tetrachloro-4H-1,2,6-thiadiazine into 4,5,6-trichloropyrimidine-2-carbonitrile.

Tin reduction of 3,4,4,5-tetrachloro-4 H -1,2,6-thiadiazine afforded perchloro-9-thia-1,5,8,10-tetraazaspiro[5.5]undeca-1,4,7,10-tetraene (10%) and 3,5-dichloro-4 H -1,2,6-thiadiazine-4-thione (27%), the structures of which were supported by single crystal X-ray crystallography. Treating the tetrachlorothiadiazine with Ph 3 P (1 equiv.) afforded the corresponding spirocycle in a useful 66% yield, the degradation of which with BnEt 3 NCl (0.5 equiv.) afforded densely functionalized 4,5,6-trichloropyrimidine-2-carbonitrile in 81% yield. Rational mechanisms for the formation of products are proposed. [ABSTRACT FROM AUTHOR]