A new synthetic approach to N-substituted 1,4-dihydropyridines

Recent developments in the chemistry of dihydropyridines

“…66 Vinylogous amidinium salts, aldehydes and malononitrile condense to form 2-amino-4H-pyrans, which on treatment with amines are smoothly converted (through a ring opening-ring closure sequence) into the corresponding 1,4-dihydropyridines. 67 Dienamines bearing ω-nitro or ester groups undergo aza-annulations with aldehydes to give 1,2-or 1,4-dihydropyridines. 68…”

Domino Reaction of 3-(2-Formylphenoxy)propenoates and Amines: A Novel Synthesis of 1,4-Dihydropyridines from Salicaldehydes, Ethyl Propiolate, and Amines

“…Sodium dithionite reduction has been largely applied to pyridinium salts bearing, in the 3- or 3,5-positions, electron-withdrawing groups such as −CN, −CONH 2 , and −COOR, and chiefly affords the corresponding 1,4-dihydropyridines . The reaction of 2-amino-5-formyl-4 H -pyran with primary amines could also yield N -substituted 1,4-DHPs .…”

Synthesis of Functionalized 4H-Pyran and Cyclohexanone Derivatives via Three-Component Reactions of Dimethyl Acetonedicarboxylate, Aromatic Aldehydes­, and Malononitrile

“…The tautomerism of the ring-closed and the ring-opened form of the 4H-pyrans 5 (Scheme 3) discloses the possibility of synthesizing our target cyclohexanone derivatives 8 and also with different substitution patterns in the phenyl nucleus. The transformation of the 2-amino-3-cyano-4-phenyl-4H-pyran ring into five-and six-membered heterocyclic compounds involving ring opening is described in the literature, [14][15][16][17][18][19][20][21][22][23] but not the formation of substituted cyclohexanones. Only the hexahydroquinolines prepared by O'Callaghan and McMurry 22 via condensation of substituted 4H-pyrans with malononitrile could be considerated as pyrido annellated cyclohexane derivatives.…”