STEREOSELECTIVE SYNTHESIS OF AND ATROPISOMERISM IN 1-PYRIDINIO)-3,4-TRANS-1,2,3,4-TETRAHYDROPYRIDINES AND THEIR TRANSFORMATION PRODUCTS

A series of yano-3,4-trans-1,2,3,4-tetrahydropyridine-6-olates were pr epared by condensation of pyridinium ylides with alpha,beta-unsaturate d carbonyl compounds or more conveniently by a three-component condens ation of pyridinium ylides, pyridine aldehydes, and ethyl cyanoacetate 3 and/or 6. This analogues of the above tetrahydropyridines were prep ared in a similar way starting from suitable substrates. Spectroscopic data revealed that the reaction leads to trans-isomers around the C3- C4 bond and is atroposelective. The conformation of and tautomerism in the tetrahydropyridines are discussed in the light of H-1 NMR data. T he reaction of -(3-pyridyl)-1,2,3,4-tetrahydropyridine-6-thiolate 10c with phenacyl bromide was found to give idyl)-6-(3-methyl-1-pyridinio) -3-phenyl-8-cyano-6, 7-trans-2,3,6,7-tetrahydrothiazol[3,2a]pyridine b romide, the crystal and molecular structure of which has been determin ed by X-ray crystallographic analysis.