Catalyst-Controlled Chemodivergent Reactions of 2-Pyrrolyl-α-diazo-β-ketoesters and Enol Ethers: Synthesis of 1,2-Dihydrofuran Acetals and Highly Substituted Indoles

A catalyst-controlled, chemodivergent reaction of pyrrolyl-α-diazo-β-ketoesters with enol ethers is reported. While Cu(II) catalysts selectively promoted a [3 + 2] cycloaddition to provide pyrrolyl-substituted 2,3-dihydrofuran (DHF) acetals, dimeric Rh(II) catalysts afforded 6-hydroxyindole-7-carboxylates via an unreported [4 + 2] benzannulation. The choice of enol ether proved to be crucial in determining both regioselectivity and yield of the respective products (up to 91% yield for Cu(II) and 82% for Rh(II) catalysis). Furthermore, the DHF acetals were shown to serve as precursors to 7-hydroxyindole-6-carboxylates (isomeric to the indoles formed from Rh) and highly substituted furans in the presence of Lewis acids. Thus, from a common pyrrolyl-α-diazo-β-ketoester, up to three unique heterocyclic scaffolds can be achieved based on catalyst selection.

1-Amino-5-(4-methyl-benzo-yl)-4-(4-methyl-phen-yl)pyrimidin-2(1H)-one

In the title compound, C₁₉H₁₇N₃O₂, the dihedral angles between the pyrimidine ring and the two benzene rings are 34.87 (12) (for the directly-bonded ring) and 69.57 (12)°. An intra­molecular N—H⋯O hydrogen bond occurs. The crystal packing features inter­molecular N–H⋯O hydrogen bonds.