We report a Chan–Lam coupling reaction of benzylic and allylic boronic esters with primary and secondary anilines to form valuable alkyl amine products. Both secondary and tertiary boronic esters can be used as coupling partners, with mono-alkylation of the aniline occurring selectively. This is a rare example of a transition-metal-mediated transformation of a tertiary alkylboron reagent. Initial investigation into the reaction mechanism suggests that transmetalation from B to Cu occurs through a single-electron, rather than a two-electron process.
General Procedure : Preparative Scale Tertiary Alkyl Chan–Lam Coupling
A flask containing the corresponding boronic ester (0.50 mmol, 1 equiv), aniline (2.00 mmol, 4 equiv), Cu(OAc)2 (0.182 g, 1.00 mmol), and Cs2CO3 (0.0820 g, 0.252 mmol) was purged with argon. Methanol (1.0 mL) and pyridine (0.33 mL) were added, and the mixture was stirred at 50 or 65 °C until the reaction was complete (as determined by TLC). The mixture was cooled to room temperature, NH4OH (10 mL) was added, and the mixture was extracted with Et2O (3 × 10 mL), dried (MgSO4), filtered, and concentrated in vacuo. The crude material was purified by column chromatography.
https://doi.org/10.1021/acs.joc.1c00976
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