Cyanogen chloride reaction with, phosgene

Perhaps the best method for conversion of carbonimidoyl dichlorides into isocyanates consists of their reaction with one equivalent of sodium methoxide, followed by thermolysis. Thus, Kodama and Sekiba obtained the triazinyl isocyanate CXXXII from tetrameric cyanogen chloride via the intermediate CXXXIII. Since N-heterocyclic isocyanates cannot be synthesized by direct phosgenation, this method may have general applicability. 

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). 

---