Ruthenium on Carbon Catalysed Carbon‐Carbon Cleavage of Aryl Alkyl Ketones and Aliphatic Aldehydes in Aqueous Media

Abstract

A new ruthenium on carbon-catalysed carbon-carbon (CÀC) cleavage reaction of aryl alkyl ketone derivatives in water in the presence of CaO under atmospheric oxygen conditions has been developed. Corresponding benzoic acid derivatives were produced from various aryl alkyl ketones in excellent yields. CaO acts as an adsorbent of CO and CO 2 to maintain a sufficient concentration of oxygen around the catalyst required for effective progress of the reaction. It was also revealed that aliphatic aldehydes were generated from the alkyl moiety of aryl alkyl ketones over the course of the reaction. The aliphatic aldehyde derivatives undergo either an oxidation to the corresponding aliphatic carboxylic acids or a further continuous CÀC cleavage reaction to form aliphatic aldehydes with loss of one carbon along with the formation of CO and CO 2 .

Aerobic Oxidative C(CO)–C Bond Cleavage under Catalyst‐Free and Additive‐Free Conditions

“…When the oxygen pressure was 0.5 MPa, 83% yield was observed (Table 1, entry 2), while no benzophenone product was obtained under the oxygen-free condition (Table 1, entry 12), suggesting that oxygen was essential. When the pressure of oxygen increased from 0.5 MPa to 1, 2 or 4 MPa, both the conversion and the yield significantly decreased (Table 1, entry 2 vs entries [15][16][17], which revealed that 0.5 MPa was the optimal pressure.…”

“…It has been reported that FeCl 3 has the ability to catalyze this transformation (Scheme 1a). [14] Other transition metal catalysts include Mn, [15] Au, [16] Ru, [17] and Rh [18] compounds. Recently, several transition metal-free methods have also been developed using base [19] or other [20] as the promoters.…”