Page 1. Pharmaceutical Society of Japan ... Pharm. Butt.39(1) 79-80 (]991) ... reaction fo11owedby aza-Wittig reactionS) to givea carbodiimide (2)as a highlyreactive 2-azahexa-1,3,5- trieneintermediate, which readily under- goes electrocyclic ring closure fo11owedby 1,3-hydrogen ...