Dihalocarbenes indole reactions

Selected examples of the reaction of pyrroles and indoles with dihalocarbenes... 

Reactions of carbanions, anions of weak organic acids (e.g., indole or carbazole), and dihalocarbenes may be carried out in liquid-liquid systems, in which concentrated aqueous sodium hydroxide is the aqueous phase. The term phase transfer catalysis is mechanistically incorrect these are often referred to as catalytic two-phase systems. Numerous reactions of carbanions including alkylation, nitroarylation, addition, the Darzens condensation, cyclopropanation, and also a variety of reactions of dihalocarbenes are conveniently carried out in this way. 

The Ciamician—Dennstedt reaction involves the addition of intermediate dihalocarbene, generated from haloforms (CHX3, X = Cl, Br, or I) and a strong base, to a pyrrole (330) to form an unstable dihalogenocyclopropane, which rearranges to a 3-halogenopyridine such as 331. The reaction was expanded for indoles to provide 3-chloroquinolines. ... 

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