Regio- and diastereoselective preparation of aldols from .alpha.-branched ketone enolates generated from BHT ester enolates and organolithium reagents. In situ generation and trapping of ketenes from ester enolates
作者:Robert Haener、Thomas Laube、Dieter Seebach
DOI:10.1021/ja00305a013
日期:1985.9
dilute solution), the corresponding silyl enol ethers with trimethylchlorosilane and aldols with aldehydes. The aldols are produced regioselectively and, in the case of unsymmetrical ketenes, diastereoselectively. Almost two dozen examples are described, illustrating the use of BHT ester enolates as nucleophilic ketene precursors. From X-ray crystal structure da t a of ester lithium enolates we could
在烷基锂化合物的存在下,由支链 2,6-二叔丁基-4-甲基苯基 (BHT) 链烷酸酯和 3 至 6 元环羧酸酯衍生的锂烯醇化物的热诱导裂解为烯酮和 LiO-BHT,苄基锂或苯基锂允许产生热力学不稳定的四取代酮烯醇化物。在选择的条件下(无酰胺碱,稀溶液),这些烯醇化物产生相应的甲硅烷基烯醇醚与三甲基氯硅烷和醛醇与醛。醛醇是区域选择性产生的,在不对称烯酮的情况下,非对映选择性产生。描述了近两打例子,说明了 BHT 酯烯醇化物作为亲核烯酮前体的用途。根据酯锂烯醇化物的 X 射线晶体结构数据,我们可以预测离去基团从 sp2 中心开始消除并形成 a 的轨迹(参见图 1 式 A 中的黑色箭头)。我们也可以制作 0002-7863/85/1507-5396$01.50/0