Enantiocontrol in intramolecular cyclopropanation of diazoketones. Conformational control of metal carbene alignment
作者:M. P. Doyle、M. Yu. Eismont、Q. L. Zhou
DOI:10.1007/bf02496127
日期:1997.5
ketones with γ or δ double bonds undergo catalytic intramolecular cyclopropanation. These reactions occur with high enantiocontrol when catalyzed by copper semicorrins and bis-oxazolines, but low enantiocontrol characterizes reactions catalyzed by a broad selection of chiral dirhodium(ii) carboxamidates. The reverse stereocontrol occurs for intramolecular cyclopropanation of allylic and homoallytic diazoacetates
具有 γ 或 δ 双键的重氮酮进行催化分子内环丙烷化。当由铜半可林和双恶唑啉催化时,这些反应以高对映控制发生,但低对映控制表征由广泛选择的手性二铑 (ii) 甲酰胺酸盐催化的反应。反向立体控制发生在烯丙基和同位重氮乙酸酯和重氮乙酰胺的分子内环丙烷化反应中。这种差异可以通过金属卡宾中间体的羰基排列(与金属同位异物)的构象控制来解释。
High Enantiocontrol in the Intramolecular Cyclopropanation of Diazo Ketones Catalyzed by Dirhodium(II) Complexes with<i> Ortho-</i>Metalated Aryl Phosphine Ligands
[reaction: see text]. Chiral dirhodium(II) complexes, Rh2(O2CCF3)2(PC)2, [PCH = (p-CH3C6H4)3P, (m-CH3C6H4)3P], provide an excellent yield and a high enantiocontrol in the cyclopropanation of alpha-diazo ketones with gamma and delta double bonds. The ee values are significantly dependent on the solvent used; the best results are obtained using pentane.
Unsaturated α-diazocarbonyl compounds undergo intramolecular cyclopropanation or carbon-hydrogen bond insertion when catalyzed by Rh2(OAc)4: α-diazoketones react preferentially with carbon-carbon doubled bond, whereas closely related α-diazo-β-keto-esters insert into carbon-hydrogen bond.
Chiral biferrocene-based bis(oxazolines): Ligands for Cu(I)-catalyzed asymmetric cyclopropanations of ene-diazoacetates
作者:Sung-Gon Kim、Chang-Woo Cho、Kyo Han Ahn
DOI:10.1016/s0040-4020(99)00542-6
日期:1999.8
Chiral biferrocene-based bis(oxazoline) compounds, which have both planar and central chirality, are synthesized. The Cu(I)-complexes of the bis(oxazolinyl)biferrocenes were found to be conformationally flexible and have a wide bite angle (136°) by NMR and molecular modeling studies. The complexes catalyzed the intramolecular cyclopropanationreaction of ene-diazoacetates, and low to moderate enantioselectivities