Condensation of pyridinium N-alkyl-, N-cycloalkyl-, N-benzyl-, and N-phenethylcarb-amoylmethylenides with ethyl arylidenecyanoacetates stereoselectively gives 4,5-trans-1-alkyl-, 4,5-trans-l-cycloalkyl-, 4,5- trans-1-benzyl-, and 4,5-trans-1-phenethyl-4-aryl-3-cyano-6-oxo-5-(3-R-1-pyridinio)-1,4,5,6-tetrahydropyridin-2-olates. However, pyridinium N-arylcarb-amoylmethylenides react with the same esters without ring closure, yielding Michael adducts, viz., ethyl 3-aryl-4-(N-arylcarbamoyl)-2-cyano-4-(1-pyridinio)butyrates.
将
吡啶鎓 N-烷基、N-
环烷基、N-
苄基和 N-
苯乙基羰基
氨基甲酰亚
甲基烯化物与亚芳基
氰基
乙酸乙酯立体选择性缩合,可得到 4、5-trans-1-alkyl-, 4,5-trans-l-cycloalkyl-, 4,5- trans-1-benzyl-, and 4,5-trans-1-phenethyl-4-aryl-3-cyano-6-oxo-5-(3-R-1-pyridinio)-1,4,5,6-tetrahydropyridin-2-olates.然而,
吡啶鎓 N-芳基
氨基甲
酰亚胺与相同的
酯类发生反应而不闭环,会产生迈克尔加合物,即 3-芳基-4-(N-芳基
氨基甲酰基)-2-
氰基-4-(1-
吡啶)
丁酸乙酯。