Haloform reaction synthetic utility

The rearrangement of pyrroles to 3-halo-pyridines upon treatment with haloforms (CHX3 where X = Cl, Br, I) in the presence of a strong base was first described by G.L. Ciamician. Its synthetic utility was later extended by M. Dennstedt to the sodium methoxide catalyzed reaction of pyrrole with methylene iodide to give pyridine. Soon after the initial discovery, the methodology was also extended for the indole series to prepare substituted quinolines. The reaction is known as the Ciamician-Dennstedt rearrangement, but it is also referred to as the abnormal Relmer-Tiemann reaction. 

The Haloform reaction is catalyzed by cyclodextrins in what the authors label as inverse phase transfer catalysis, 25 but the synthetic utility of this variation remains to be seen. An alternative to the use of halogen is a nitroarene catalyzed oxidation of acetophenone with sodium percarbonate or sodium perborate.26 However, the yields of substituted benzoic acids furnished by this method are mediocre (23-73%) in comparison to the conventional Haloform conditions. Likewise, the Haloform reaction of acetone with iodine in liquid ammonia is without synthetic merit (8-12%).27... 

The synthetic utility of the Haloform reaction is revealed further by a synthesis of isotopically pure (99.2%) CDCb by the reaction of trichloroacetophenone with NaOD in D20. The alkoxide-cleavage of trichloromethyl ketones has been employed to synthesize dihydropyridine esters (e.g., 24) in which ester exchange does not occur.59... 

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