The thermal decomposition of E-3-azido-3-hexene-2, 5-dione (1) in protic media gave rise to several novel reactions of the azide 1 including adducts derived from keteneimine 11. Reaction with t-butyl mercaptan yielded two products, keteneimine-derived mercaptan addition product 20 and a sulfenimine 6. Trapping of a vinyl nitrene intermediate or a thio- Staudinger reaction was considered as a possible mechanism for the formation of ...