Asymmetric hydrogenation of trisubstituted olefins with iridium-phosphine thiazole complexes:: A further investigation of the ligand structure
Asymmetric hydrogenation of trisubstituted olefins with iridium-phosphine thiazole complexes:: A further investigation of the ligand structure
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DOI：
10.1021/ja057178b
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发表时间：
2006-03-08
影响因子：
15
通讯作者：
Andersson, PG
中科院分区：
文献类型：
--
作者：
Hedberg, C;Källström, K;Andersson, PG
制备了新型手性双齿膦噻唑，并成功地作为配体应用于均相铱催化芳烯和芳烯酯的不对称加氢反应。这些配体被设计成高度模块化，并且具有一个共同的手性中间体，可以在合成途径的后期阶段引入多样性。研究发现，刚性配体结构的六元环主链优于七元环或五元环主链。本研究表明，配体的取代基模式对产物的立体化学结果有重要影响。应用本研究提出的选择性模型，可以实现不同底物对不同催化剂的匹配。通过这种方法，可以对典型的困难底物获得良好至优异的对映体选择性。通过几何上不同的-甲基肉桂酸乙酯和-甲基肉桂酸乙酯衍生物的氢化，验证了选择性模型的有效性，并验证了催化剂和底物的空间和电子匹配的重要性。
New chiral bidentate phoshine thiazoles have been prepared and successfully applied as ligands in the homogeneous iridium-catalyzed asymmetric hydrogenation of aryl alkenes and aryl alkene esters. The ligands are designed to be highly modular and have one common chiral intermediate, from which diversity can be introduced at a late stage in the synthetic pathway. It was found that a six-member-ring backbone of the rigid ligand structure was preferred over seven- or five-member rings. In this study it is shown that the substituent pattern of the ligands has a major influence on the stereochemical outcome of the products. By applying the selectivity model proposed in this study, it is possible to match different substrates against different catalysts. In this way, good to excellent enantioselectivity can be obtained for typically difficult substrates. Geometrically different derivatives of alpha- and beta-methyl cinnamic acid ethyl esters were hydrogenated, to demonstrate the validity of the selectivity model and to verify the importance of steric and electronic matching of the catalyst and the substrate.