Application of chiral ligands: carbohydrates, nucleoside-lanthanides and other Lewis acid complexes to control regio- and stereoselectivity of the dipolar cycloaddition reactions of nitrile oxides and esters
作者:Mirosław Gucma、W. Marek Gołębiewski、Maria Krawczyk
DOI:10.1039/c4ra15975f
日期:——
and (Z)-pent-2-en-1-yl esters were examined. Excellent enantioselectivities with moderate to good regioselectivities were achieved for crotonates with complexes of BiBr3 with (+)-(4,6-benzylidene)methyl-α-D-glucopyranoside C, with the L-ascorbic acid I–FeCl3 system, and with lipase Candida antarctica. High enantiomeric excess was observed for isopropyl ester and benzyl ester. The outstanding ee values
考察了手性路易斯酸介导的4-三氟甲基苄腈氧化物与巴豆酸甲酯以及β-取代的丙烯酸酯和(Z)-戊-2-烯-1-基酯的1,3-偶极环加成反应。丁烯酸与BiBr 3与(+)-(4,6-亚苄基)甲基-α - D-吡喃葡萄糖苷C的配合物,L-抗坏血酸I- FeCl 3体系的配伍丁烯酸酯具有出色的对映选择性和中等至良好的区域选择性用脂肪酶念珠菌南极洲。对于异丙酯和苄基酯,观察到高对映体过量。β- t丙烯酸酯具有出色的ee值C -Yb(OTf)3和(+)-2-羟基-3-吡喃酮N -TiCl 4体系催化的环加成反应中的丁基,环己基和1,3-苯并二恶酚-5-基。在由络合物N –Mg(OTf)2和N –TiCl 4介导的(Z)-戊-2-烯-1-基酯的反应中发现高对映选择性。