DIRHODIUM(II) TETRAKIS(CARBOXAMIDATES) WITH CHIRAL LIGANDS - STRUCTURE AND SELECTIVITY IN CATALYTIC METAL CARBENE TRANSFORMATIONS
DIRHODIUM(II) TETRAKIS(CARBOXAMIDATES) WITH CHIRAL LIGANDS - STRUCTURE AND SELECTIVITY IN CATALYTIC METAL CARBENE TRANSFORMATIONS
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具有手性配体的四(羧酰胺酸)二铑(ii)--在催化金属碳烯转化中的结构和选择性
DOI：
10.1021/ja00075a013
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发表时间：
1993-11-03
影响因子：
15
通讯作者：
GHOSH, R
中科院分区：
文献类型：
--
作者：
DOYLE, MP;WINCHESTER, WR;GHOSH, R
对手性二铑(II)四(2-氧代吡咯烷-5-甲酸甲酯)、Rh2(5S-MEPY)4 和 Rh2(5R-MEPY)4 (5) 以及二铑(II)四(4-苄基-2-恶唑烷酮)、Rh2(4R-BNOX)4 和Rh2(4S-BNOX)4 (6)，以确定和了解它们作为金属卡宾转化中对映体控制催化剂的相对有效性。报告了这些二铑 (II) 化合物的合成、光谱特征和 X 射线结构。 每个都有两个氧供体原子和两个氮供体原子，与每个八面体铑结合，氮配体呈顺式取向。 Rh2(MEPY)4 催化剂在分子间和分子内环丙烷化反应、分子间环丙烯化反应以及重氮乙酸酯和重氮乙酰胺的分子内 C-H 插入反应中提供高水平的对映体控制方面明显比 Rh2(BNOX)4 更有效，通常可达到 >90% 对映体过量。分子力学计算能够重现Rh2(5S-MEPY)A和Rh2(4R-BNOX)4的X射线结构，已被用来获得中间体金属卡宾的优选构象，但环丙烷化产物的绝对构型与从优选金属卡宾构象预测的绝对构型相反。然而，苯乙烯-卡宾复合物的构象能量最小值预测了观察到的对映体偏好。
Structure-selectivity comparisons are made between chiral dirhodium(II) tetrakis(methyl 2-oxopyrrolidine-5-carboxylates), Rh2(5S-MEPY)4 and Rh2(5R-MEPY)4 (5), and dirhodium(II) tetrakis(4-benzyl-2-oxazolidinones), Rh2(4R-BNOX)4 and Rh2(4S-BNOX)4 (6), to ascertain and understand their relative effectiveness as catalysts for enantiocontrol in metal-carbene transformations. The syntheses, spectral characteristics, and X-ray structures for these dirhodium(II) compounds are reported. Each possesses two oxygen- and two nitrogen-donor atoms bound to each octahedral rhodium with a cis orientation of the nitrogen ligands. The Rh2(MEPY)4 catalysts are significantly more effective than those of Rh2(BNOX)4 in providing a high level of enantiocontrol in intermolecular and intramolecular cyclopropanation reactions, in intermolecular cyclopropenation reactions, and in intramolecular C-H insertion reactions of diazoacetates and diazoacetamides, often reaching >90% enantiomeric excesses. Molecular mechanics calculations that were able to reproduce the X-ray structures of Rh2(5S-MEPY)A and Rh2(4R-BNOX)4 have been employed to obtain the preferred conformation of the intermediate metal-carbene, but the absolute configurations of cyclopropanation products are opposite to those predicted from the preferred metal-carbene conformation. However, conformational energy minima of the styrene-carbene complex predict the observed enantiomer preference.