Synthesis of NewC2-Symmetrical Bissulfonamide Ligands and Application in the Enantioselective Addition of Alkynylzinc to Aldehydes and Ketones
作者:Ming Ni、Rui Wang、Zhi-jian Han、Bin Mao、Chao-shan Da、Lei Liu、Chao Chen
DOI:10.1002/adsc.200505162
日期:2005.10
achieved. So far the most economic catalyst system was developed for the addition of terminal alkynes to aromatic aldehydes in terms of ligand loading and enantioselectivity. Moreover, ligand 7a in combination with Ti(O-i-Pr)4 was found to be effective in promoting the addition reaction of an alkynylzinc reagent to unactivated simple ketones under very mild conditions. The corresponding chiral tertiary propargylic
新颖的C 2-对称双磺酰胺配体易于通过三个简单步骤制备,并用于炔基锌试剂对醛的对映选择性加成。发现化合物7a是该反应的杰出配体。当使用4mol%的7a的催化剂负载量时,在非常温和的条件下获得了ee值高达97%的高对映选择性。当配体7a的量降低至2mol%时,仍达到高达95%ee的优异对映体控制水平。迄今为止,已开发出最经济的催化剂体系,用于在配体负载和对映选择性方面向芳族醛中添加末端炔烃。此外,配体7a发现与Ti(O - Pr)4组合可以有效地促进炔基锌试剂在非常温和的条件下与未活化的简单酮的加成反应。得到相应的手性叔炔丙醇,其对映体过量最高为81%。