Olefin cyclopropanation and insertion into OH bonds mediated by copper(I) and palladium(II) covalently anchored to silica xerogels

Copper(I) and palladium(II) ligated to pyrazolylpyridine bearing a tethered (trimethoxysilyl)propyl group in position 4 of the pyrazole ring were chemically bonded to silica via a sol-gel process. The textural properties of the materials (specific surface area, porous volume, and pore size distribution) were characterized by nitrogen adsorption-desorption isotherms, mercury porosimetry, and TEM analysis. The hybrid materials were tested as catalysts in olefin cyclopropanation and as potential chemoselective catalysts in the reaction with unsaturated alcohols (double bond versus OH group), with ethyl diazoacetate as a carbene precursor, and compared with the corresponding homogeneous complexes.