Yet another example of a S N 1-like S E Ar reaction is found in the biosynthetic pathway for vitamin B 12 . The electrophile is generated by loss of ammonia (instead of pyrophosphate as in the previou...Yet another example of a S N 1-like S E Ar reaction is found in the biosynthetic pathway for vitamin B 12 . The electrophile is generated by loss of ammonia (instead of pyrophosphate as in the previous examples) from the first of two substituted aromatic rings:
