Oxidant-Free C(sp2)–H Functionalization/C–O Bond Formation: A Kolbe Oxidative Cyclization Process
摘要:
An anodic oxidation/cyclization of 2-arylbenzoic acids for the synthesis of dibenzopyranones has been developed. The reaction proceeds at room temperature with no oxidant or electrolyte required and exhibits a high atom economy with H-2 being the only byproduct. A series of dibenzopyranones was obtained in good to excellent yields. Urolithins A, B, and C are formally synthesized by adopting this method as a key step to demonstrate its synthetic utility.
Silver-catalyzed C(sp(2))-H functionalization/CO cyclization has been developed. The scalable reaction proceeds at room temperature in an open flask. The present method exhibits good functional-group compatibility because of the mild reaction conditions. Using a AgNO3 catalyst and a (NH4)(2)S2O8 oxidant in CH2Cl2/H2O solvent, various lactones are obtained in good to excellent yields. A kinetic isotope effect (KIE) study indicates that the reaction may occur via a radical process.