Department of Chemistry, University of Toronto, 80 St. George St. Toronto, Ontario (Canada) http://www.chem.utoronto.ca/staff/ML/index.php.
Angew Chem Int Ed Engl. 2014 Jul 21;53(30):7908-12. doi: 10.1002/anie.201404007. Epub 2014 Jun 10.
The use of Pd catalysis as a means to synthesize organic halides has recently received increased attention. Among the reported methods is the Pd-catalyzed carboiodination, which uses extremely bulky ligands to facilitate carbon-halogen reductive elimination from Pd(II) as the key catalytic step. When approaching substrates exhibiting low stereoselectivity, catalyst troubleshooting becomes difficult as there are few ligands known to promote the key reductive elimination. Herein, we present our finding that tertiary amines act as weakly coordinating ligands which significantly enhance diastereoselectivity in the Pd/QPhos-catalyzed carboiodination of chiral N-allyl carboxamides. This methodology allows efficient access to enantioenriched and densely functionalized dihydroisoquinolinones, and has been applied toward the asymmetric formal synthesis of (+)-corynoline.
钯催化作为合成有机卤化物的一种手段，最近受到了越来越多的关注。已报道的方法之一是钯催化的碳卤化反应，该反应使用极其庞大的配体来促进钯(II)的碳-卤键还原消除，这是关键的催化步骤。当接近立体选择性较低的底物时，由于很少有配体被认为能促进关键的还原消除，因此催化剂故障排除变得困难。在这里，我们发现叔胺作为弱配位配体，可以显著提高手性 N-烯丙基酰胺的钯/QPhos 催化碳卤化反应的非对映选择性。该方法可有效地获得对映体富集和高度官能化的二氢异喹啉酮，并已应用于(+)-考来啉的不对称形式合成。
