Deux types de participation ? lors de l'hydrolyse des diazoc�tones ?, ?-insatur�es par des acides aqueux et des superacides. L'ion oxo-5-norbornyle-2
作者:Roger Malherbe、Hans Dahn
DOI:10.1002/hlca.19740570822
日期:——
γ, δ-Unsaturated diazoketones undergo acid catalysed hydrolysis accompanied by cyclisation; the latter is favoured by suitable geometry (cyclopentenes) and by substitution by methyl groups. If both are present, rate enhancement by anchimeric assistance has been observed. Hydrolysis of 4-diazoacetyl-cyclopentene (1) yields a product mixture similar to that formed during solvolysis of 5-oxo-norbornyl-2-endo
α-Diazoacetates as Carbene Precursors: Metallosalen-Catalyzed Asymmetric Cyclopropanation
作者:Tsutomu Katsuki、Tatsuya Uchida
DOI:10.1055/s-2006-926448
日期:2006.5
Readily available α-diazo compounds have been shown to be efficient carbene precursors for asymmetric cyclopropanation using ruthenium(NO)-salen and cobalt-salen complexes, as catalysts. The stereoselectivity of the cyclopropanation depends on the metal ion, its valency, the structural and electronic nature of the salen ligand, and the apical ligand of the salen complex used. Both trans- and cis-selective asymmetric intermolecular cyclopropanation can be realized under mild conditions by using a suitable metallosalen complex. Furthermore, a wide range of alkenyl α-diazoacetates and the related alkenyl diazomethyl ketones undergo intramolecular cyclopropanation in a highly enantioselective manner by using various metallosalen complexes, easily prepared in a modular fashion, as catalyst.
Ru(II)-catalyzed asymmetric cyclopropanation using chiral diphenylphosphino(oxazolinyl)quinoline ligands
作者:Sang-Wook Park、Jeong-Ho Son、Sung-Gon Kim、Kyo Han Ahn
DOI:10.1016/s0957-4166(99)00190-1
日期:1999.5
ines were synthesized starting from 2-cyano-8-hydroxyquinoline. These N,N,P-chelates were successfully employed in the Ru(II)-catalyzedasymmetriccyclopropanation reactions of diazo-alkenes. The catalytic system exhibited good reactivity and high thermal stability and provided high yields in the intramolecular cyclopropanation, albeit somewhat decreased enantioselectivities compared to known catalytic
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.