Divergent Reactions of α‑Diazo 1,3-Dicarbonyl\nCompounds with Allylic Carbonates Involving Ketene versus Carbene\nIntermediates Enabled by Cooperative Rh(II)/Pd(0) Dual Catalysis

A cooperative Rh(II)/Pd(0) dual-catalysis\nstrategy that enabled\ndivergent reactions of α-diazo 1,3-dicarbonyl compounds with\nallylic carbonates involving ketene versus carbene intermediates is\ndescribed. The efficient synthesis of α-quaternary allylated\nβ-keto-esters was accomplished by the Rh(II)/Pd(0) dual-catalysis\nallylic alkylation of α-diazo 1,3-dicarbonyl compounds. Alternatively,\nan unprecedented (1+4) annulation of α-diazo 1,3-dicarbonyl\ncompounds with 2-(hydroxymethyl)allyl carbonates via Rh(II)/Pd(0)\ndual catalysis was also successfully developed, affording a wide variety\nof α-quaternary tetrahydrofurans in good to high yields.