Homochiral ketals in organic synthesis. Diastereoselective cyclopropanation of α,β-unsaturated ketals derived from 1,4-D1-O-benzyl-l-threitol
作者:Eugene A. Mash、Keith A. Nelson
DOI:10.1016/s0040-4020(01)90002-x
日期:——
2-Cycloalken-1-one 1,4-di --benzyl -L-threitol ketals undergo efficient and diastereoselective cyclopropanation when treated with an excess of the Simmons-Smith reagent. For example, 2-cyclohexen-1-one 1,4-di --benzyl -L-threitol ketal gave in 90-98% yield a 9:1 mixture of diastereomeric cyclopropanes as established by 62.9 MHz 13C NMR spectroscopy and by hydrolysis of the mixture to (1,6)-bicyclo[4
当用过量的Simmons-Smith试剂处理时,2-Cycloalken-1-one 1,4-二--苄基-L-苏糖醇缩酮会发生高效且非对映选择性的环丙烷化。例如,由62.9 MHz 13 C NMR光谱法和水解确定,2-环己烯-1-酮1,4-二-苄基-L-苏糖醇缩酮的收率为90-98%,为非对映体环丙烷的9:1混合物将混合物制成(1,6 )-双环[4.1.0]庚烷-2-酮。给出了十六个其他实例,这些实例证明了2-环烯-1-酮缩酮的制备方法的一般性和可预测性,因为不幸的是,它对α,β-不饱和1,4-二-苄基-L-苏糖醇缺乏非对映选择性乙缩醛。
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.