Chichibabin pyridine synthesis | |
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Named after | Aleksei Chichibabin |
Reaction type | Ring forming reaction |
Identifiers | |
RSC ontology ID | RXNO:0000526 |
The Chichibabin pyridine synthesis ( /ˈtʃiːtʃiːˌbeɪbiːn/ ) is a method for synthesizing pyridine rings. The reaction involves the condensation reaction of aldehydes, ketones, α,β-unsaturated carbonyl compounds, or any combination of the above, with ammonia. [1] It was reported by Aleksei Chichibabin in 1924. [2] [3] Methyl-substituted pyridines, which show widespread uses among multiple fields of applied chemistry, are prepared by this methodology. [4]
The syntheses are presently conduced commercially in the presence of oxide catalysts such as modified alumina (Al2O3) or silica (SiO2). The reactants are passed over the catalyst at 350–500 °C. 2-Methylpyridine- and 4-methylpyridine are produced as a mixture from acetaldehyde and ammonia. 3-Methylpyridine and pyridine are produced from acrolein and ammonia. Acrolein and propionaldehyde react with ammonia affords mainly 3-methylpyridine. 5-Ethyl-2-methylpyridine is produced from paraldehyde and ammonia. [5]
These syntheses involve many reactions such as imine synthesis, base-catalyzed aldol condensations, and Michael reactions.
Many efforts have been made to improve the method. [6] [1] Conducting the reaction in the gas phase in the presence of aluminium(III) oxide. [4] zeolite (yield 98.9% at 500 K), [7]
Of the many variations have been explored. one approach employs nitriles as the nitrogen source. For example, acrylonitrile and acetone affords 2-methylpyridine uncontaminated with the 4-methyl derivative. In another variation, alkynes and nitriles react in the presence of organocobalt catalysts, a reaction inspired by alkyne trimerization. [5]