Enantioselective pinacol coupling of aryl aldehydes catalyzed by chiral Salan-Mo(IV) complexes.
Enantioselective pinacol coupling of aryl aldehydes catalyzed by chiral Salan-Mo(IV) complexes.
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DOI：
10.1021/jo701842r
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发表时间：
2007-11
期刊：
影响因子：
--
通讯作者：
Hongwei Yang;Hongsong Wang;Chengjian Zhu
中科院分区：
文献类型：
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作者：
Hongwei Yang;Hongsong Wang;Chengjian Zhu
本文报道了芳香醛与手性 Salan-Mo(VI) 二氧配合物作为有效预催化剂的不对称频哪醇偶联。获得的手性二醇具有高非对映选择性和对映选择性，分别高达 92/8 和 95%。研究了频哪醇与催化体系偶联反应的可能机理。通过X射线光电子能谱研究确定了催化剂前体Mo(L3)O2的X射线晶体结构，并确定中间体C的氧化态为+4。所提出的机制推测了反应的立体化学结果，并提出了 E 自由基偶联的工作模型，该模型解释了 dl 异构体的首选 (S,S)-对映体的绝对构型。
Reported herein is the asymmetric pinacol coupling of aromatic aldehydes with chiral Salan-Mo(VI) dioxo complex as an effective precatalyst. Chiral diols were obtained with high diastereoselectivity and enantioselectivity up to 92/8 and 95%, respectively. The possible mechanism of the pinacol coupling reaction with the catalytic system was investigated. The X-ray crystal structure of the precatalyst Mo(L3)O2 was determined and the oxidation state of the intermediate C was confirmed as +4 with X-ray photoelectron spectroscopy study. The proposed mechanism speculated the stereochemical outcome of the reaction, and a working model for the radical coupling of E was proposed, which explained the absolute configuration of the favored (S,S)-enantiomer of the dl isomer.