Organocatalytic Stereoselective α-Alkylation of Aldehydes with Stable Carbocations
作者:Fides Benfatti、Elena Benedetto、Pier Giorgio Cozzi
DOI:10.1002/asia.201000160
日期:2010.9.3
stereoselective alkylation of aldehydes is carried out with the four stable carbocations 1, 2, 3, 4 in the presence of a catalytic amount (20 mol%) of MacMillan imidazolidinones 5, 6. In all reactions, lutidine was used as a base. The alkylation reactions are investigated at different temperatures with linear and branched aldehydes. In the case of carbocation tropylium fluoroborate, an interesting
醛的有机催化的立体选择性烷基化是用四个稳定碳阳离子进行1,2,3,4麦克米兰的在催化量的存在(20%摩尔)咪唑啉酮5,6。在所有反应中,二甲基吡啶被用作碱。用直链和支链醛在不同温度下研究烷基化反应。在碳正离子对氟硼酸叔丁基酯的情况下,观察到烷基化产物构型的有趣逆转,这是由反应中的熵效应驱动的。获得通过化学相关性来确定,发现产品的绝对构型为与由麦克米伦提出的模型一般协议来证明在由型催化剂促进了反应得到的立体选择性5,6。