phosphine–nickel complex and an axially chiral sodium dicarboxylate has been developed. The transformation features mild reaction conditions, a broad substrate scope, and excellent functional group tolerance, offering an efficient approach to an array of enantioenriched O-propargyl hydroxylamines. Mechanistic studies support the presumed role of the chiral carboxylate as a counterion for nickel catalysis enabling
已经开发了通过结合膦-镍络合物和轴向手性二羧酸钠催化的高度对映选择性的 O-炔丙基化。该转化具有温和的反应条件、广泛的底物范围和出色的官能团耐受性,为一系列富含对映体的O-炔丙基羟胺提供了一种有效的方法。机理研究支持手性羧酸盐作为镍催化的抗衡离子的假定作用,从而能够发现高度立体选择性的转化。该反应的威力通过其在强效萤火虫萤光素酶抑制剂和 ( S )-二氢yashabushiketol 的不对称全合成中的应用来说明。
Chlorine, an atom economical auxiliary for asymmetric aldol reactions
作者:Shira D. Halperin、Robert Britton
DOI:10.1039/c3ob27462d
日期:——
An auxiliary strategy has been developed for asymmetricreactions of aldehydes in which the auxiliary itself is not chiral, but a single chlorine atom introduced via organocatalytic α-chlorination. The stereodirecting influence of the chlorine atom is then exploited prior to its removal by radical reduction. This strategy is demonstrated in the synthesis of several aldols (92–99% ee) and the natural
Absolute Configuration of Platyphylloside and (−)-Centrolobol
作者:Shinji Ohta、Mika Koyama、Tadashi Aoki、Takayuki Suga
DOI:10.1246/bcsj.58.2423
日期:1985.8
The absoluteconfiguration of platyphylloside was established to be S by 13C NMR spectroscopy. On the basis of this establishment, the S-configuration previously assigned to the chirality at C-3 of (−)-centrolobol was revised to the R-configuration.
Enantiomerically pure (+)-(5S)-dihydroyashabushiketol 1a was obtained by the 1,3-dipolar cycloaddition of a nitrile oxide, generated from oxime 3b, to N-acryloyl bornane[10,2]sultam (2R)-2 (67%, 85% de, then crystallization 81%, 99% de), followed by reduction with DIBAL-H to aldehyde (-)-6a (67%), Wittig reaction to isoxazoline (E/Z)-7 (60%), and finally hydrolytic hydrogenation (62%). (C) 2011 Elsevier Ltd. All rights reserved.
Kuroyanagi, Masanori; Noro, Tadataka; Fukushima, Seigo, Chemical and pharmaceutical bulletin, 1983, vol. 31, # 5, p. 1544 - 1550