Directed <i>ortho</i> C–H borylation catalyzed using Cp*Rh(<scp>iii</scp>)–NHC complexes
作者:Jompol Thongpaen、Thibault E. Schmid、Loic Toupet、Vincent Dorcet、Marc Mauduit、Olivier Baslé
DOI:10.1039/c8cc03144d
日期:——
bidentate NHC-carboxylate ligands were efficiently synthesized and fully characterized including solid-state structures. These unprecedented rhodium(III) complexes demonstrated high selectivity in pyridine-directed ortho-C–H borylation of arenes under mild conditions.
Supported phosphine-Rh systems, prepared in situ from silica-supported bridgehead monophosphines and [Rh(OH)(cod)]2, have enabled ortho-selective C-H borylation for a range of arenes containing nitrogen-based directing groups. The regioselectivity was excellent with various N-directing groups, including saturated and unsaturated N-heterocycles, tert-aminoalkyl groups, and iminetype C-N double bonds. The reaction showed significant tolerance toward steric repulsion around the reacting C-H bond. This Rh catalysis complements the Jr-catalyzed orthoborylation, which is effective for arenes with oxygen-based directing groups.