Iridium-Catalyzed Asymmetric Borylation of Unactivated Methylene C(sp3)-H Bonds
Herein, we show the highly enantioselective borylation of unactivated methylene C(sp3)-H bonds in 2-alkylpyridines and 2-alkyl-1,3-azole derivatives using an iridium-BINOL-based chiral monophosphite catalyst system. Quantum chemical calculations using the artificial force induced reaction (AFIR) method suggested that a monophosphite-Ir-tris(boryl) complex generates a narrow chiral reaction pocket where the differentiation of the enantiotopic methylene C-H bonds is accomplished through an assembly of multiple noncovalent interactions.
Reyes, Ronald L.,Iwai, Tomohiro,Maeda, Satoshi,Sawamura, Masaya
Enantioselective Rh- or Ir-catalyzed directed C(sp3)H borylation with phosphoramidite chiral ligands
Enantioselective heteroatom-directed C(sp3)H borylation reactions of 2-aminopyridines and 2-alkylpyridines with Rh- and Ir catalytic systems using commercially available chiral monophosphine ligands, respectively, were developed. This methodology provides an innovative example of a homogeneous catalytic system for C(sp3)H borylation, and allows the direct synthesis of optically active alkylboronates with a moderate level of enantioselectivity.
Reyes, Ronald L.,Harada, Tomoya,Taniguchi, Tohru,Monde, Kenji,Iwai, Tomohiro,Sawamura, Masaya
Iridium-Catalyzed Asymmetric Borylation of Unactivated Methylene C(sp3)-H Bonds
Herein, we show the highly enantioselective borylation of unactivated methylene C(sp3)-H bonds in 2-alkylpyridines and 2-alkyl-1,3-azole derivatives using an iridium-BINOL-based chiral monophosphite catalyst system. Quantum chemical calculations using the artificial force induced reaction (AFIR) method suggested that a monophosphite-Ir-tris(boryl) complex generates a narrow chiral reaction pocket where the differentiation of the enantiotopic methylene C-H bonds is accomplished through an assembly of multiple noncovalent interactions.
Reyes, Ronald L.,Iwai, Tomohiro,Maeda, Satoshi,Sawamura, Masaya
supporting information
(2019/05/08)
Synthesis of primary and secondary alkylboronates through site-selective C(sp3)-H activation with silica-supported monophosphine-Ir catalysts
The site-selective activation and borylation of unactivated C(sp3)-H bonds in 2-alkylpyridines to form primary and secondary alkylboronates was achieved using silica-supported monophosphine-Ir catalysts. This borylation occurs selectively at C-H bonds located γ to the pyridine nitrogen atom. The site-selectivity of this reaction suggests that the C-H bond cleavage occurs with the assistance of a proximity effect due to N-to-Ir coordination.