Aryl Bromides as Inexpensive Starting Materials in the Catalytic Enantioselective Arylation of Aryl Aldehydes: The Additive TMEDA Enhances the Enantioselectivity
作者:Yong-Xin Yang、Yue Liu、Lei Zhang、Yan-E Jia、Pei Wang、Fang-Fang Zhuo、Xian-Tao An、Chao-Shan Da
DOI:10.1021/jo502070r
日期:2014.11.7
We used aryl bromides as inexpensive starting materials to enantioselectively arylate aldehydes in one pot. Aryl bromides readily transfer aryls to aryllithiums with n-butyllithium, successively to triarylaluminums with aluminum chloride, and then to aryltitaniums with titanium isopropoxide. Finally aryltitaniums arylate aldehydes catalyzed by (S)-H-8-BINOLTi(Oi-Pr)(2) in excellent yields and enantioselectivities. The additive TMEDA evidently suppresses the racemic background reaction promoted by LiCl generated from salt metathesis. This procedure represents a cost-effective and operationally convenient method for enantioenriched diarylmethanols.
From Aryl Bromides to Enantioenriched Benzylic Alcohols in a Single Flask: Catalytic Asymmetric Arylation of Aldehydes
作者:Jeung Gon Kim、Patrick J. Walsh
DOI:10.1002/anie.200600741
日期:2006.6.19
Practical Catalytic Asymmetric Synthesis of Diaryl-, Aryl Heteroaryl-, and Diheteroarylmethanols
作者:Luca Salvi、Jeung Gon Kim、Patrick J. Walsh
DOI:10.1021/ja9046747
日期:2009.9.2
successfully added to aldehydes and heteroaryl aldehydes with enantioselectivities between 81-99%. These are the first examples of catalytic and highly enantioselective syntheses of diheteroarylmethanols. In a similar fashion, ferrocenyl bromide was used to generate FcZnEt and the ferrocenyl group added to benzaldehyde and heteroaromatic aldehydes to form ferrocene-based ligand precursors in 86-95%
对映体富集的二芳基、芳基杂芳基和二杂芳基甲醇表现出重要的生物和医学特性。介绍了从容易获得的芳基溴开始,一锅催化不对称合成这些化合物。因此,溴化锂与市售芳基溴化物和n-BuLi进行交换,然后与ZnCl(2)进行盐复分解以生成ArZnCl。添加第二当量的正丁基锂以形成混合有机锌 ArZnBu。在对映体富集的氨基醇基催化剂存在下,ArZnBu 与醛加成,基本上得到外消旋的二芳基甲醇。低对映选择性归因于 LiCl 促进的背景反应。为了抑制这种背景反应,在添加醛之前引入螯合二胺 TEEDA(四乙基乙二胺)。在这些条件下,获得了对映体富集的二芳基甲醇,其 ee 大于 90%。烯醛的芳基化生成具有 81-90% ee 的烯丙醇。然而,当应用于杂芳基溴时,该过程并不成功,这归因于杂芳基锂在盐复分解条件下的分解。为了避免这个问题,用EtZnCl进行复分解,这使得盐复分解可以在低温下进行。所得的 EtZn(Ar(杂))