Mechanism of heterocyclic ring expansions. Part III. Reaction of pyrroles with dichlorocarbene
2,5-Dimethyl-, 2,3,4,5-tetramethyl-, and 3,4-dimethyl-2,5-diphenyl-1H-pyrrole react with dichlorocarbene in basic solution to give 2-dichloromethyl-2H-pyrrole and 3-chloropyridines in low yield. However, in neutral aprotic solution high yields of 3-chloropyridines are formed in a synthetically useful reaction; 2H-pyrroles are not formed.
These results support earlier mechanistic proposals.