Efficient Synthesis of Piperidine Derivatives. Development of Metal Triflate-Catalyzed Diastereoselective Nucleophilic Substitution Reactions of 2-Methoxy- and 2-Acyloxypiperidines
作者:Osamu Okitsu、Ritsu Suzuki、Shū Kobayashi
DOI:10.1021/jo001297m
日期:2001.2.1
Nucleophilic substitution reactions of 2-methoxy- and 2-acyloxypiperidines were investigated. First, new and efficient methods for the preparation of the starting piperidine derivatives were developed. N-Benzyloxycarbonyl-2-methoxypiperidine (3) and 3-substituted-2-acyloxy-N-benzyloxycarbonylpiperidines (4a-d), which are recognized as the simplest imino-sugars, were prepared and were examined as substrates
研究了2-甲氧基-和2-酰氧基哌啶的亲核取代反应。首先,开发了用于制备起始哌啶衍生物的新的有效方法。制备被认为是最简单的亚氨基糖的N-苄氧基羰基-2-甲氧基哌啶(3)和3-取代的-2-酰氧基-N-苄氧基羰基哌啶(4a-d)并作为亲核取代反应与甲硅烷基烯醇盐在催化量的金属三氟甲磺酸酯(Sc(OTf)3,Sn(OTf)2,Cu(OTf)2,Hf(OTf)4等)的影响下。在测试的三氟甲磺酸酯中,Sc(OTf)3给出了最佳结果。发现2-乙酰氧基-3-苄氧基-N-苄氧基羰基哌啶(4a)与烯丙基甲硅烷基酯反应得到高顺式选择性的2-烷基化加合物,而2,3-二酰氧基-N-苄氧基羰基哌啶(4b-d)显示出反选择性。使用NMR分析,X射线晶体学和合成转化过程仔细进行了立体化学分配。在这些非对映选择性亲核取代反应的基础上,由2,3-二乙酰氧基-N-苄氧基羰基哌啶(4b)成功合成了强效抗疟生物碱Febrifugine(1)。