Murakami R, Tsunoda K, Iwai T, Sawamura M * Hokkaido University, Sapporo, Japan
Stereoselective C–H Borylations of Cyclopropanes and Cyclobutanes with Silica-Supported Monophosphane–Ir Catalysts.
Chem. Eur. J. 2014;
20: 13127-13131
Key words
borylation - cyclopropanes - cyclobutanes - silica gel supported phosphines - iridium
Significance
The heteroatom-directed C–H borylation of cyclopropanes and cyclobutanes with bis(pinacolato)diboron was carried out in the presence of [Ir(OMe)(cod)]2 and silica-SMAP to give the corresponding borylated products in up to 168% yield based on bis(pinacolato)diboron (eqs. 1 and 2).
Comment
In the reaction of 2-cyclopropylpyridine with bis(pinacolato)diboron, the catalytic activity of the silica-SMAP–iridium system was superior to that of the other ligand–iridium systems (for example, 0% yield for Ph-SMAP–Ir, Me3P–Ir, t-Bu3P–Ir, Ph3P–Ir, XPhos–Ir, dtbpy–Ir, and 2,9-Me2Phen–Ir).
