Synthetic applications of N–N linked heterocycles. Part 14. The preparation of α-(4-pyridyl)esters and α-(4-pyridyl)nitriles by regiospecific attack of ester and nitrile anions on pyridinium salts
作者:Michael P. Sammes、Cheuk Man Lee、Alan R. Katritzky
DOI:10.1039/p19810002476
日期:——
Reactions between N-(2,6-dimethyl-4-oxopyridin-1-yl)pyridinium tetrafluoroborate (1) and lithio-derivatives of esters and nitriles give only low yields of 1,4-dihydro-adducts (3) and (7) due apparently to competing proton abstraction from the pyridone methyl groups. This limitation with salt (1) appears only with C–H acids of pKa > 20. Decomposition of the adducts under free-radical conditions yields
之间的反应ñ - (2,6-二甲基-4-氧代吡啶-1-基)吡啶鎓四氟硼酸盐(1)和酯的锂代衍生物和腈得到的1,4-二氢加合物仅低收率(3)和(7 )显然是由于从吡啶酮甲基中竞争质子的提取。盐(1)的这种限制仅在p K a > 20的CHH酸出现。在自由基条件下加合物的分解产生α-(4-吡啶基)-酯(4)和-腈(8)数量上。通过合适的锂盐和N-三苯基甲基吡啶鎓盐之间的反应,可以方便地以良好的总收率制备相同的吡啶基酯和-腈。讨论了该方法的范围和局限性。2-甲基-N首次报道了四氟硼酸-三苯基甲基吡啶鎓。