Ruthenium(II) Porphyrin Catalyzed Formation of (Z)-4-Alkyloxycarbonyl- methylidene-1,3-dioxolanes from γ-Alkoxy-α-diazo-β-ketoesters

Ruthenum(II) porphyrins and dirhodium(II) acetate catalyze cyclization of γ-alkoxy-α-diazo-β-ketoesters to (Z)-4-(alkyloxycarbonylmethylidene)-1,3-dioxolanes selectively (ca. 68% yield) with no formation of 3(2H)-furanones. Reacting a diazo ketoester with [Ru^II(TTP)(CO)] [H₂TTP = meso-tetrakis(p-tolyl) porphyrin] in toluene afforded a ruthenium carbenoid complex, which has been isolated and spectroscopically characterized. A mechanism involving hydrogen atom migration from the C−H bond to the ruthenium carbenoid is proposed.