Catalyst-Controlled Intermolecular Homobenzylic C(sp<sup>3</sup>)–H Amination for the Synthesis of β-Arylethylamines
Erwan Brunard, Vincent Boquet, Tanguy Saget, E. Daiann Sosa Carrizo, Marie Sircoglou, Philippe Dauban
Abstract
The combination of a tailored sulfamate with a C 4 -symmetrical rhodium(II) tetracarboxylate allows to uncover a selective intermolecular amination of unactivated homobenzylic C(sp 3 )–H bonds. The reaction has a broad scope (>30 examples) and proceeds with a high level of regioselectivity with homobenzylic/benzylic ratio of up to 35:1, thereby providing a direct access to β-arylethylamines that are of utmost interest in medicinal chemistry. Computational investigations evidenced a concerted mechanism, involving an asynchronous transition state. Based on a combined activation strain model and energy decomposition analysis, the regioselectivity of the reaction was found to rely mainly on the degree of orbital interaction between the [Rh 2 ]–nitrene and the C–H bond. The latter is facilitated at the homobenzylic position due to the establishment of specific noncovalent interactions within the catalytic pocket.