An environmentally friendly method for synthesis of amides is presented where a simple ruthenium catalyst mediates the direct coupling between an alcohol and an amine with the liberation of two molecules of dihydrogen. The active catalyst is generated in situ from an easily available ruthenium complex, an N-heterocyclic carbene and a phosphine. The reaction allows primary alcohols to be coupled with primary alkylamines to afford the corresponding secondary amides in good yields. The amide formation presumably proceeds through a catalytic cycle where the intermediate aldehyde and hemiaminal are both coordinated to the metal catalyst.

No abstract

No abstract

Wine into vinegar: It is possible to selectively oxidize ethanol into acetic acid in aqueous solution with air as the oxidant and a heterogeneous gold catalyst (see TEM image of supported gold particles) at temperatures of about 423 K and O2 pressures of 0.6 MPa. This reaction proceeds readily in aqueous acidic media with yields of up to 90 % and CO2 as the only major by‐product.

The mechanism for the rhodium-catalyzed decarbonylation of aldehydes was investigated by experimental techniques (Hammett studies and kinetic isotope effects) and extended by a computational study (DFT calculations). For both benzaldehyde and phenyl acetaldehyde derivatives, linear Hammett plots were obtained with positive slopes of +0.79 and +0.43, respectively, which indicate a buildup of negative charge in the selectivity-determining step. The kinetic isotope effects were similar for these substrates (1.73 and 1.77 for benzaldehyde and phenyl acetaldehyde, respectively), indicating that similar mechanisms are operating. A DFT (B3LYP) study of the catalytic cycle indicated a rapid oxidative addition into the C(O)-H bond followed by a rate-limiting extrusion of CO and reductive elimination. The theoretical kinetic isotope effects based on this mechanism were in excellent agreement with the experimental values for both substrates, but only when migratory extrusion of CO was selected as the rate-determining step.