Tetrahydropyridines and Dihydropyridines

Tetrahydropyridines and Dihydropyridines. A review article covering dihydropyridine chemistry has appeared. l-Benzyl-l,2,5,6-tetrahydrop)U idines (366) may be obtained by sodium borohydride reduction of 1-benzylpyri-dinium salts (367). They react with phenoxycarbonyl chloride to give l-phenoxycarbonyl-l,2,5,6-tetrahydropyridines (368) and with phosgene to give 1-chlorocarbonyl derivatives (369). 1,2,5,6-Tetrahydropyridines (370) can be recovered from (368) and (369) by alkaline and acid hydrolysis, respectively.  

Dauphin, L. David, B. Jamilloux, A. Kergomard, and H. Veschambre, Tetrahedron, 

AT-Methoxycarbonyl-1,2- and -1,4-dihydropyridines (378) may be prepared by reducing pyridine with sodium borobydride in tbe presence of metbyl 

It has been shown that 1,4-dihydropyridines are more stable than their 1,2-isomers. Equilibration of the iV-methyl derivatives with l.OM-KOBu in DMSO at 91.6 °C shows that the 1,4-isomer is 2.29 0.01 kcal moH more stable. 

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