Hydroaminoalkylation of Unactivated Olefins with Dialkylamines
The intermolecular addition of the α-C−H bonds of unactivated dialkylamines to unactivated olefins in the presence of the chloro amido complex [TaCl3(NEt2)2]2 (2) is described. This process forms the branched insertion products in high yields (up to 96%) and selectivities, and represents a rare example of an intermolecular amine-olefin coupling reaction that does not require preactivation of either substrate. The reaction is shown to encompass the addition of the primary C−H bonds in linear- and branched-methylamines, as well as secondary C−H bonds in higher dialkylamines. The related chloroanilido complex [TaCl3(NMePh)2]2 (4) is also shown to catalyze the addition of N-alkyl-arylamines to olefins at temperatures as low as 90 °C. 1H NMR spectroscopy, identification of the catalyst structure, and deuterium-labeling experiments all suggest that reactions catalyzed by 2 and 4 occur by turnover-limiting generation of an η2-imine complex. These labeling studies also imply that more favorable partitioning of the η2-imine complex toward reaction with alkene versus regeneration of the starting bis-amido complex accounts for the higher reactivity of the mixed halide amido catalyst versus a homoleptic amido complex.
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