ASYMMETRIC-SYNTHESIS USING TARTRATE ESTER MODIFIED ALLYLBORONATES .1. FACTORS INFLUENCING STEREOSELECTIVITY
ASYMMETRIC-SYNTHESIS USING TARTRATE ESTER MODIFIED ALLYLBORONATES .1. FACTORS INFLUENCING STEREOSELECTIVITY
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DOI：
10.1021/jo00300a031
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发表时间：
1990-06-22
影响因子：
3.6
通讯作者：
PARK, JC
中科院分区：
文献类型：
--
作者：
ROUSH, WR;HOONG, LK;PARK, JC
本文详细研究了影响酒石酸烯丙基硼酸酯与1-手性和非手性醛反应对映体和非对映选择性的因素。这些反应的立体选择性对以下变量很敏感，如反应温度(最佳结果总是在-78℃)、溶剂(甲苯对脂肪醛最好；四氢呋喃对芳香醛最好)和水分(建议使用分子筛以保持无水反应环境)，但对酒石酸酯的结构没有影响。酒石酸烯丙基硼酸酯1已被发现比以前研究的其他烯丙基硼酸盐具有异常的活性，甚至非常受阻的底物(例如，新戊醛)的反应在-78℃下在几个小时内就能完成。C.描述了一种合成1的改进方法，包括烯丙基溴化镁与(IPro)3B的反应，然后与DIPT的水解和酯化。采用这种新工艺，1，2，4-二苯基-1，4-二苯基-4，4，4，4，4，4-三甲基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-苯基-2-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-苯基-描述了一种对1的解进行标准化的简单方法。最后，通过与不对称环氧化制备的环氧醇的关联，对5个高烯丙醇(5a-e)的绝对立体化学进行了归属。这些关联的结果与我们1985年出版的立体化学图景完全一致。
A detailed study of the factors that influence the enantio- and diastereoselectivity of the reactions of tartrate allylboronate with 1 chiral and achiral aldehydes is reported. The stereoselectivity of these reactions is sensitive to variables such as reaction temperature (best results invariably are obtained at -78.degree.C), solvent (toluene is best for aliphatic aldehydes; THF is preferred for aromatic aldehydes), and moisture (use of molecular sieves is recommended to maintain an anhydrous reaction environment), but not on the structure of the tartrate ester. Tartrate allylboronate 1 has been found to be exceptionally reactive compared to other, previously studied allylboronates, and even the reaction of very hindered substrates (e.g., pivalaldehyde) are complete within several hours at -78.degree.C. An improved method for synthesis of 1 is described that involves the reaction of allylmagnesium bromide with (iPrO)3B followed by aqueous hydrolysis and esterification with DIPT. Yields of 1 are considerably higher (65-76%) by using this new procedure, and the crude reagent so prepared may be used directly in allylboration experiments. A simple method for standardizing solutions of 1 is described. Finally, the absolute stereochemistry of five homoallylic alcohols (5a-e) were assigned by correlation with epoxy alcohols prepared via the Sharpless asymmetric epoxidation. The results of these correlations are in complete agreement with the stereochemical picture presented in our 1985 publication.