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

Ruthenum(II) porphyrins and dirhodium(II) acetate catalyze cyclization of γ-alkoxy-α-diazo-β-ketoesters to (<i>Z</i>)-4-(alkyloxycarbonylmethylidene)-1,3-dioxolanes selectively (ca. 68% yield) with no formation of 3(<i>2H</i>)-furanones. Reacting a diazo ketoester with [Ru^II(TTP)(CO)] [H₂TTP = <i>meso</i>-tetrakis(<i>p</i>-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.