Azides, guanyl synthesis

The formation of guanyl azide (IV) at the first stage may account for the formation of tetrazene by the action of nitrous acid on aminoguanidine, i.e. by Hoffmann synthesis. 

A one-pot protocol for the synthesis of 1-aryl-5-(N-aryl-N-aroylamino)-tetrazoles 247 from symmetrical diaryl carbodiimides 243 with sodium azide under phase transfer conditions in toluene at room temperature was developed by Ding and Weber. The carbodiimide 243 reacts with sodium azide to form a guanyl azide 244 which, after reaction with an aroyl chloride 245, imdergoes electrocycHzation to yield the substituted tetrazole 247 (Scheme 47). The reaction is limited to symmetrical diaryl carbodiimides. Di-aUcyl carbodiimides fail to react imder these conditions while asymmetrical diaryl carbodiimides lead to a mixture of tetrazole isomers [157]. 

---