Kawamorita S, Miyazaki T, Ohmiya H, Iwai T, Sawamura M * Hokkaido University, Sapporo, Japan
Rh-Catalyzed
Ortho-Selective C–H Borylation
of
N-Functionalized Arenes with Silica-Supported Bridgehead Monophosphine Ligands.
J. Am. Chem. Soc. 2011;
133: 19310-19313
Key words
rhodium - C–H activation - borylation - SMAP - silica-supported catalysis
Significance
ortho-C–H Borylation of N-functionalized arenes with solid-supported Rh catalysts was described. A Rh complex prepared in situ from [Rh(OH)(cod)]2 and silica-SMAP (a silica-supported 1-phospha-4-silabicyclo[2.2.2]octane derivative)
was found to promote the ortho-borylation efficiently. In the presence of 0.5 mol% Rh (Rh/P = 1:1), the reaction of 2-phenylpyridine (1) with bis(pinacolato)diborone (2) gave 2-(2-pyridyl)phenylboronic acid pinacol ester
(3) in 98% yield based on 2.
Comment
In the presence of Ph-SMAP (4-phenyl-1-phospha-4-silabicyclo[2.2.2]octane) instead of silica-SMAP, product 3 was obtained in only 17% GC yield. The catalyst was readily separated from the reaction mixture by filtration using Celite,
although attempts to reuse the catalyst were unsuccessful.
