Regio- and Enantioselective Iridium-Catalyzed Amination of Racemic Branched Alkyl-Substituted Allylic Acetates with Primary and Secondary Aromatic and Heteroaromatic Amines

摘要

The air- and water-stable pi-allyliridium C,O-benzoate modified by (S)-tol-BINAP, (S)-Ir-II, catalyzes highly regio-and enantioselective Tsuji-Trost-type aminations of racemic branched alkyl-substituted allylic acetates using primary or secondary (hetero)aromatic amines. Specifically, in the presence of (S)-Ir-II (S mol%) in DME solvent at 60-70 degrees C, alpha-methyl allyl acetate la (100 mol%) reacts with primary (hetero)aromatic amines 2a-2l (200 mol%) or secondary (hetero)aromatic amines 3a-3l (200 mol%) to form the branched products of allylic amination 4a-4l and 5a-5l, respectively, as single regioisomers in good to excellent yield with uniformly high levels of enantioselectivity. As illustrated by the conversion of heteroaromatic amine 3m to adducts 6a-6g, excellent levels of regio-and enantioselectivity are retained across diverse branched allylic acetates bearing normal alkyl or secondary alkyl substituents. For reactants 3n-3p, which incorporate both primary and secondary aryl amine moieties, regio-and enantioselective amination occurs with complete site selectivity to furnish adducts 7a-7c. Mechanistic studies involving amination of the enantiomerically enriched, deuterium labeled acetate lh corroborate C-N bond formation via outer-sphere addition.