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

The air- and water-stable π-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 (5 mol%) in DME solvent at 60–70 °C, α-methyl
allyl acetate 1a (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 1h corroborate C–N bond formation via outer-sphere
addition.