Catalytic enantioselective hetero Diels-Alder reactions of α,β-unsaturated acyl phosphonates with enol ethers
Catalytic enantioselective hetero Diels-Alder reactions of α,β-unsaturated acyl phosphonates with enol ethers
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DOI：
10.1021/ja980423p
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发表时间：
1998-05-20
影响因子：
15
通讯作者：
Johnson, JS
中科院分区：
文献类型：
--
作者：
Evans, DA;Johnson, JS
该实验室之前的报告已经记录了阳离子 C2 对称 Cu (II) 双（恶唑啉） 1 配合物 1 和 2 作为手性路易斯酸的用途，能够催化许多具有高对映选择性的 Diels-Alder2 和 aldol3 反应。在这些过程中，统一的组织基序是经历活化的底物能够与手性阳离子 Cu (II) 催化剂螯合，这种条件通常提供高对映选择。 4 本文的目的是介绍我们的研究结果，即 R1-不饱和酰基膦酸酯在手性 Cu (II) 配合物 1 和 2 的催化下与烯醇醚发生对映选择性杂狄尔斯-阿尔德反应 5，得到环状烯醇膦酸酯 (eq 1)，这些化学实体被证明是不对称合成的有用构件。本研究选择酰基膦酸酯的前提是有利的酰基膦酸盐-催化剂缔合可能是通过邻近的 CdO 和 PdO 官能团之间的络合来实现的。事实上，我们发现配合物 1 和 2 可以活化酰基膦酸酯 3a-d，使其与富电子烯烃发生容易的环加成反应（表 1）。 6-8 乙基乙烯基醚(4)与巴豆酰膦酸酯3a在[Cu((S,S)-tert-Bu-box)](OTf)2存在下的反应
Previous reports from this laboratory have documented the utility of cationic C2-symmetric Cu (II) bis (oxazoline) 1 complexes 1 and 2 as chiral Lewis acids capable of catalyzing a number of Diels-Alder2 and aldol3 reactions with high enantioselectivities. In these processes, the unifying organizational motif is that the substrate undergoing activation is capable of chelating to the chiral cationic Cu (II) catalyst, a condition that frequently affords high enantioselection. 4 The purpose of this paper is to present our findings that R,-unsaturated acyl phosphonates undergo enantioselective hetero Diels-Alder reactions5 with enol ethers catalyzed by chiral Cu (II) complexes 1 and 2 to afford cyclic enol phosphonates (eq 1), chemical entities that are shown to be useful building blocks for asymmetric synthesis.The selection of acyl phosphonates for this study was made on the premise that favorable acyl phosphonate-catalyst association might be achieved via complexation between the vicinal CdO and PdO functional groups. Indeed, it was found that complexes 1 and 2 activate acyl phosphonates 3a-d to the extent that they undergo facile cycloaddition reactions with electron-rich alkenes (Table 1). 6-8 The reaction of ethyl vinyl ether (4) with crotonyl phosphonate 3a in the presence of [Cu ((S, S)-tert-Bu-box)](OTf) 2