Chichibabin reaction catalysts

Pyridine bases such as 3-picoline and MEP are predominantly manufactured by the Chichibabin reaction, where a mixture of aldehydes or ketones is reacted with ammonia. Thus, formaldehyde, acetaldehyde and ammonia react in the gas phase to produce a mixture of pyridine and 3-picoline. By choosing the appropriate aldehyde or ketone, catalyst and phase (liquid or gas phase), the composition of the mixture can be varied at will, depending on the desired end-product. In the gas phase, silica alumina catalysts are often used, while in the liquid phase acid catalysts based on phosphoric or acetic acid are employed. In the 1990s, Reilly patented MET and BEA-based zeolite catalyst compositions for ammonia-aldehyde conversions to pyridine, picolines and alkyl pyridines. 

Good yields of tetrahydro-5//-pyrido[2,3-6]azepines (186) are obtained by intramolecular Sn2 Chichibabin type reaction of <5-(3-pyridyl)butyIamines in the presence of various basic catalysts (73JHC39). 

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