One-pot synthesis of substituted benzo[b]furans from mono- and dichlorophenols using palladium catalysts bearing dihydroxyterphenylphosphine.

A dihydroxyterphenylphosphine bearing cyclohexyl groups on the phosphorus atom (Cy-DHTP) was found to be a powerful ligand for the palladium-catalyzed one-pot synthesis of substituted benzo[b]furans from 2-chlorophenols and terminal alkynes. This catalyst system was also applicable to the sequential one-pot synthesis of disubstituted benzo[b]furans from dichlorophenols via the Suzuki-Miyaura cross-coupling of chlorobenzo[b]furan with boronic acids. The use of two ligands, Cy-DHTP and XPhos, is the key to promoting the reactions. Mechanistic studies suggest that the Pd-Cy-DHTP catalyst is the active species in the Sonogashira cross-coupling step, while the Pd-XPhos catalyst accelerates the Suzuki-Miyaura cross-coupling step.