Iridium‐Catalyzed Regio‐ and Enantioselective Borylation of Unbiased Methylene C(sp³)−H Bonds at the Position β to a Nitrogen Center

Abstract

Reported herein is the pyrazole‐directed iridium‐catalyzed enantioselective borylation of unbiased methylene C−H bonds at the position β to a nitrogen center. The combination of a chiral bidentate boryl ligand, iridium precursor, and pyrazole directing group was responsible for the high regio‐ and enantioselectivity observed. The method tolerated a vast array of functional groups to afford the corresponding C(sp3)−H functionalization products with good to excellent enantioselectivity.

Coordination-assisted, transition-metal-catalyzed enantioselective desymmetric C–H functionalization

“…Very recently, the Xu group reported a pyrazole-directed Ir(I)-catalyzed enantioselective β-borylation of unbiased methylene C(sp 3 )-H bonds (Scheme 40b). 85 Notably, the high regio-and enantioselectivity strongly depended on the choice of the chiral bidentate boryl ligand, iridium precursor, and pyrazole directing group. Moreover, this pyrazole directing group could be readily elaborated into chiral vicinal diamine derivative via ozonolysis.…”

2-Aminophenanthrolines Enable the Mild, Undirected Borylation of Alkyl C–H Bonds

“…Such reactions have required higher temperatures and superstoichiometric quantities of substrate, [6][7][8][9][10][11][12] except for reactions of activated alkyl C H bonds in cyclopropanes, 13 in methylarenes, 14 or nearby a directing group. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] The photochemical and electrochemical borylations of alkyl C H bonds occur at mild temperatures but have required high loadings of the substrate or metal. [30][31][32][33] These limitations have prevented the widespread adoption of alkyl C H borylation by synthetic chemists.…”