No abstract

The direction of the reaction of derivatives of N-ethoxycarbonylmethylpyridinium The ability of quaternized pyridinium salts to form pyridinium ylides, capable of entering into cycloaddition reactions at the multiple bonds, during the action of bases is widely used in organic synthesis [1][2][3][4][5]. The initial product of the cycloaddition of the pyridinium ylide at the activated carbon--carbon double bond is a derivative of tetrahydroindolizine [1, 4]. This is often oxidized during isolation to the corresponding derivatives of dihydroindolizine [3] and indolizine [1]. As a rule tetrahydroindolizines are unstable compounds. However, a series of derivatives of tetrahydroindolizine, synthesized from ethoxycarbonylmethylpyridinium, carbamoylmethylpyridinlum, and cyanomethylpyridinium salts and also from the corresponding quinolinium salts by treatment with bases in the presence of various chalcones, were described in [4]..Among the substituted pyridines o~-,/~-, and ~,-picolinium salts were tested. Derivatives of tetrahydroindolizine were only isolated in the reactions with unsubstituted pyridine and c~-picoline.In the present work we investigated the effect of the 1,4-dihydropyridyl (1,4-DHP) substituent (as a weak electron donor) and the pyridyl substituent (as an electron acceptor) on the above-mentioned reactions.