Previous transition metal-catalyzed synthesis processes of δ-diketones are plagued by the high cost of the rhodium catalyst and harsh reaction conditions. Herein a low-cost, roomtemperature ruthenium catalytic method is developed based on the coupling of α-keto sulfoxoniumylides with cyclopropanols. The mild protocol features a broad substrate scope (47 examples) and a high product yield (up to 99%)