Parallel Synthesis of a Library of Benzoxazoles and Benzothiazoles Using Ligand-Accelerated Copper-Catalyzed Cyclizations of ortho-Halobenzanilides
Ghotas Evindar and Robert A. Batey*
*Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6, Email: rbateychem.utoronto.ca
G. Evindar, R. A. Batey, J. Org. Chem., 2006, 71, 1802-1808.
DOI: 10.1021/jo051927q (free Supporting Information)
see article for more reactions
A general method for the formation of benzoxazoles and benzothiazoles via a copper-catalyzed cyclization of ortho-haloanilides is reported. Optimal conditions for cyclization used a catalyst combination of CuI and 1,10-phenanthroline as ligand. The mechanism is believed to proceed via an oxidative insertion/reductive elimination pathway through a Cu(I)/Cu(III) manifold. The rate of reaction of ortho-haloanilides follows the order I > Br > Cl, consistent with oxidative addition being the rate-determining step.
see article for more examples
R. D. Viirre, G. Evindar, R. A. Batey, J. Org. Chem., 2008, 73, 3452-3459.