Dual-activation asymmetric strecker reaction of aldimines and ketimines catalyzed by a tethered bis(8-quinolinolato) aluminum complex
(Chemical Equation Presented) An aluminum complex was found to be high yielding and enantioselective for the addition of cyanide to aldimines and ketimines. Although catalytic asymmetric addition of cyanide to imines to generate ?-amino-protected nitriles (the Strecker reaction) has been extensively studied in the past, alternative, easier-to-handle reagents for this process are required for modern organic synthesis. To date, there are a limited number of reports utilizing alternative sources of cyanide other than KCN/HCN or TMSCN for this important reaction. The present catalyst provides uniformly high enantioselectivity for aromatic, heteroaromatic, and aliphatic aldimines and ketimines using ethyl cyanoformate as the cyanide source.
Nitroxyl-Radical-Catalyzed Oxidative Coupling of Amides with Silylated Nucleophiles through N-Halogenation
A nitroxyl-radical-catalyzed oxidative coupling reaction between amines with an N-protecting electron-withdrawing group (EWG) and silylated nucleophiles was developed to furnish coupling products in high yields, thus opening up new frontiers in organocatalyzed reactions. This reaction proceeded through the activation of N-halogenated amides by a nitroxyl-radical catalyst, followed by carbon–carbon coupling with silylated nucleophiles. Studies of the reaction mechanism indicated that the nitroxyl radical activates N-halogenated amides, which are generated from N-EWG-protected amides and a halogenation reagent, to give the corresponding imines.