| |
[摘要]：Lewis acid (ZnI2) - promoted Mannich reaction of azetidin-2-one - tethered aldimines 3a-r with silylenol ether 4 in toluene at -20 degrees C afforded a diastereomeric mixture of beta-amino acid esters 5a-r/6a-r. The effect of the amount of zinc(II) iodide, equimolar (100 mol%) and catalytic (20 mol%), on the chemical yield and the product stereoisomeric ratio was studied. The diastereoselective Mannich reaction of imine 3a with silylenol ether 4 at low temperature (-20 degrees C) in toluene under equimolar zinc(II) iodide catalysis provided the best chemical yield - 99% combined with the highest diastereoselectivity of beta-amino acid esters 5a/6a 85:15%. Furthermore, the influence of various groups on azetidin-2-one - tethered imines 3a-r (R-1 = phenyl, ferrocenyl; R-2 = alkyl, aryl, ferrocenyl) has been applied in the Mannich reaction leading to the formation of two stereoisomers of beta-amino acid esters 5a-r/6a-r with diastereomeric ratio varying from 92:8 to 59:41%. |
|
