A new, non‐symmetrical copper(II) pincercomplex catalyzes much more efficiently the formation of benzofuran by the reaction between ortho‐iodophenols and alkynes. The lowest catalyst loadings are realized for this reaction, and bromo‐ and chlorophenols are heteroannulated for the first time. Strong evidence for hydrophenoxylation and intramolecular halogen atom‐transfer steps catalyzed by this remarkably
Impregnated copper or palladium–copper on magnetite as catalysts for the domino and stepwise Sonogashira-cyclization processes: a straightforward synthesis of benzo[b]furans and indoles
作者:Rafael Cano、Miguel Yus、Diego J. Ramón
DOI:10.1016/j.tet.2011.12.042
日期:2012.2
An impregnated copper on magnetite catalyst is a versatile system for different domino Sonogashira-cyclization processes between 2-iodophenol and different alkynes to give the corresponding substituted benzo[b]furans. The catalyst could be recovered ten times without losing its activity. The related process using 2-iodoaniline was, however, better catalyzed by mixed palladium–copper on magnetite giving