Catalytic Approach to Diverse α‐Aminoboronic Acid Derivatives by Iridium‐Catalyzed Hydrogenation of Trifluoroborate‐Iminiums

Enantioselective synthesis of cyclic α-aminoboronates via copper-catalyzed dearomative borylation of 4-quinolinols

A highly enantioselective and regioselective dearomative borylation of 4-quinolinols was developed using a Cu(I)/(R,R)-Ph-BPE catalyst for efficient synthesis of unprecedented heterocyclic α-amino boronates, a new class of compounds potentially relevant to drug discovery, in generally excellent yields and enantioselectivities. The products were also useful intermediates for highly functionalized tetrahydroquinolines and cyclic α-aminoboronate derivatives.

Primary trifluoroborate-iminiums enable facile access to chiral α-aminoboronic acids via Ru-catalyzed asymmetric hydrogenation and simple hydrolysis of the trifluoroborate moiety

This work describes the first preparation and application of primary trifluoroborate-iminiums (pTIMs) as a new, easily accessible and valuable class of organoboron derivatives. An array of structurally diverse pTIMs was prepared from potassium acyltrifluoroborates in excellent yields. Highly efficient and enantioselective [(R,R)-TethTsDpen-RuCl] complex-catalyzed hydrogenation of pTIMs provided direct access to chiral primary trifluoroborate-ammoniums (pTAMs). Moreover, facile synthesis of a series of structurally diverse chiral α-aminoboronic acids from chiral pTAMs was accomplished through novel, operationally simple and efficient conversion using hexamethyldisiloxane/aqueous HCl. Using no chromatography at any point, this work allowed easy access to chiral α-aminoboronic acids, as exemplified by the synthesis of optically pure anti-cancer drugs bortezomib and ixazomib.

Starting with potassium acyltrifluoroborates (KATs), N-unprotected chiral α-aminoboronic acids are prepared in three simple steps without chromatography. This facile methodology will tap the broad potential of these valuable compounds.