Catalytic Asymmetric α-Iminol Rearrangement: New Chiral Platforms
作者:Xin Zhang、Richard J. Staples、Arnold L Rheingold、William D. Wulff
DOI:10.1021/ja5065685
日期:2014.10.8
A series of 19 different asymmetric catalysts were screened in an effort to identify the first chiral catalyst for the rearrangement of α-hydroxy imines to α-amino ketones involving a 1,2-carbon shift. Although aluminate complexes of VAPOL, VANOL, and 7,7′-tBu2VANOL were quite effective catalysts giving up to 88% ee, the ne plus ultra catalyst for this reaction was found to be a zirconium complex of
筛选了一系列 19 种不同的不对称催化剂,以确定第一个手性催化剂,用于将 α-羟基亚胺重排为 α-氨基酮,涉及 1,2-碳位移。尽管 VAPOL、VANOL 和 7,7'-tBu2VANOL 的铝酸盐配合物是非常有效的催化剂,可提供高达 88% 的 ee,但发现用于该反应的 ne plus 超催化剂是 VANOL 的锆配合物,可提供 97 至 >99% ee 对于大多数检查的底物。该催化剂的 X 射线衍射研究表明,锆以具有三个 VANOL 配体和两个质子化 N-甲基咪唑的均配配合物形式存在。
[(S)-BINAP]PdBr2-catalyzed direct synthesis of 2,3-disubstituted indoles via a tandem reaction between arylamines and α-diketones
A direct PdBr2(BINAP)-complex catalyzed method has been developed to produce 2,3-disubstituted indoles by the reaction of arylamines with alpha-diketones under reductive (H-2) conditions. The synthetic methodology involves a tandem reaction of three steps and all the organic intermediates were isolated and characterized, the reduction products in this sequence are chiral and present interesting enantiomeric excess. This report constitutes a new and different route to synthesize indoles and a plausible mechanism is also suggested. (C) 2011 Elsevier Ltd. All rights reserved.
Catalytic Asymmetric Acyloin Rearrangements of α-Ketols, α-Hydroxy Aldehydes, and α-Iminols by <i>N</i>,<i>N</i>′-Dioxide–Metal Complexes
N′-dioxide complex as catalyst. This strategy provided an array of optically active 2-acyl-2-hydroxy cyclohexanones in moderate to good yields with high enantioselectivities. The asymmetric isomerizations of acyclic α-hydroxy aldehydes and α-iminols were achieved as well under modified conditions, affording the corresponding chiral α-hydroxy ketones and α-amino ketones in moderate results. Moreover, further