The Hantzsch pyridine synthesis or Hantzsch dihydropyridine synthesis is a multi-component organic reaction between an aldehyde such as formaldehyde, 2 equivalents of a β-keto ester such as ethyl acetoacetate and a nitrogen donor such as ammonium acetate or ammonia.[1][2] The initial reaction product is a dihydropyridine which can be oxidized in a subsequent step to a pyridine.[3] The driving force for this second reaction step is aromatization. This reaction was reported in 1881 by Arthur Rudolf Hantzsch.
At least five significant pathways have been proposed for the Hantzch reaction synthesis of 1,4-dihydropyridine. Low yield and unexpected products may arise under varying reactants and reaction conditions. Previous studies have tested the reactions of preformed intermediates to determine the most likely mechanism and design successful syntheses.[6] An early study into the mechanism using 13C and 15N NMR indicated the intermediacy of the chalcone 6 and enamine 3. This data suggested the following route for the reaction.[7]
organic reaction mechanism ahluwalia pdf 38
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