N-aryl-2-hydroxy-1,2,3,4-tetrahydropyridines and N-aryl-2-chloromethylene-1,2,3,4-tetrahydropyridines — successive intermediates in the Hantzsch synthesis of 1,4-dihydropyridines

Esters of 4-chloro-2-arylideneacetoacetic acid I and esters of N-arylaminocrotonic acid II form stable N-aryl-3,4-trans-2-hydroxy-1,2,3,4-tetrahydropyridines III. Their regio- and stereoselective dehydration results in N-aryl-2-chloromethylene-1,2,3,4-tetrahydropyridines with an exocyclic bond, IV. Compounds IV isomerize to the corresponding N-aryl-2-chloromethyl-1,4-dihydropyridines V in acid medium. Michael addition of compounds I and II in chloroform or benzene forms carbocyclic derivatives of cyclohexene VI.Latvian Institute of Organic Synthesis, Riga LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 915–920, July, 1997.