Direct, Catalytic Hydroaminoalkylation of Unactivated Olefins with N-Alkyl Arylamines
A tantalum-catalyzed addition of N-alkyl arylamine α-C−H bonds across olefins is reported. These reactions occur with mono- and 2,2-disubstituted olefins to form the branched insertion products in high yield and regioselectivity. The reactions encompass additions of the α-C−H bonds of cyclic and acyclic amines, as well as intramolecular additions. NMR studies indicate that the starting homoleptic, Ta(NMe2)5 precatalyst converts to bis- and tris(N-methylanilide) complexes (among others) in solution. Deuterium-labeling studies suggest that reversible ortho-metalation of the arene substituent occurs under the reaction conditions. However, several experiments imply that this ortho-metalation does not lie on the reaction pathway. Instead, these complexes are proposed to eliminate amine to form N-aryl imine complexes, which insert olefins into the Ta−C bond and undergo protonolysis to regenerate the active catalyst and eliminate the addition product.
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