An Enantioselective Entry to Substituted 6-Membered Nitrogen Heterocycles from Chiral Pyridinium Salts via Selective Epoxidation of Tetrahydropyridine Intermediates
作者:Laurent Gil、Delphine Compère、Bérangère Guilloteau-Bertin、Angèle Chiaroni、Christian Marazano
DOI:10.1055/s-2000-8712
日期:——
reagent. Epoxides such as 15, 16 and 19 are unstable but they can be deprotonated by LDA to give allylic alcohols such as 28, 30 or 32. These alcohols turned out to be potentially useful synthons, whose further oxidation or conversion to enones (29, 31) allows, in principle, introduction of a number of substituents on the piperidine ring. In particular, this is exemplified by a five-steps synthesis, from
使用全三氟乙酸作为试剂,手性 2 和 2,6-取代的 1,2,5,6-四氢吡啶 6、11、12 和 21 的环氧化反应以良好至高的立体选择性和优异的收率进行。15、16 和 19 等环氧化物不稳定,但它们可以被 LDA 去质子化,得到烯丙醇,如 28、30 或 32。这些醇被证明是潜在有用的合成子,其进一步氧化或转化为烯酮 (29, 31 ) 原则上允许在哌啶环上引入许多取代基。具体地,这通过从手性四氢吡啶6以26%的总产率合成四取代哌啶7的五步合成来举例说明。