Regioselective addition of organomagnesium reagents to N-silyl activated nicotinic acid esters—a convenient method for the synthesis of 4,4-disubstituted 1,4-dihydronicotinates
作者:Christian A. Sperger、Klaus T. Wanner
DOI:10.1016/j.tet.2009.05.008
日期:2009.7
The addition of RMgX or R2Mg to nicotinic acid esters, activated with triisopropylsilyl triflate, was investigated. The regioselectivity of this reaction, where 4-unsubstituted and 4-substituted pyridine derivatives were employed as starting materials, was examined. Depending on the structure of the organomagnesium reagent varying ratios of 1,2-, 1,4-, and 1,6-regioisomers were obtained but in any
研究了将RMgX或R 2 Mg添加到被三氟甲磺酸三异丙基甲硅烷基酯活化的烟酸酯中。检查了该反应的区域选择性,其中使用4-未取代的和4-取代的吡啶衍生物作为起始原料。取决于有机镁试剂的结构,获得了1,2-,1,4-和1,6-区域异构体的不同比率,但是在任何情况下1,4-加成产物显然都是主要的。异构体纯加成产物与LiOH的甲硅烷基化可提供稳定的4,4-二取代的二氢吡啶,这些化合物很容易用卤代烷以高收率进行N-烷基化。此外,显示出所获得的二氢吡啶的甲硅烷基保护基可以容易地被酰基取代。