Silica-supported HClO4 promotes catalytic solvent- and metal-free O--H insertion reactions with diazo compounds.

Solvent-free O-H insertion reactions in the presence of diazo carbonyl compounds were carried-out in very mild conditions. Unlike the traditional metal-catalysed version, employing rhodium acetate dimer, this method uses eco-friendly silica-supported HClO4 as the catalyst. Only 0.3 mol% of this Brønsted acid catalyst, that can also be recycled several times, is necessary to guarantee very good yields (up to 97%) in the O-H insertion reactions. Reaction set-up is simple and permitted the preparation of forty-three α-hydroxyand α-alkoxy esters/ketones in just 1 h and at room temperature. [ABSTRACT FROM AUTHOR]