Copper-catalyzed cyclopropanation of 1,2,3,4-tetrahydropyridin-2-ones with diazoacetates - A facile and stereoselective synthesis of 3-oxo-2-azabicyclo [4.1.0] heptanes

The reactions of a series of 1,2,3,4-tetrahydropyridin-2-ones (1) with diazoacetates (2) in the presence of copper-bronze catalyst yielded exclusively 3-oxo-2-azabicyclo [4.1.0] beptanes (3 and 4) in excellent yields with high exo-selectivity. Tetrahydropyridin-2-ones (1) with N-alkyl substituents were found to be more reactive than N-aryl substitutents. Among the various copper catalysts studied, copper(II) triflate was found to be the best catalyst while rhodium chloride, ruthenium chloride did not catalyze the reaction. The application of ultrasonic radiation enhanced the reaction rate and allowed the reactions to be conducted at room temperature. (C) 2003 Elsevier B.V. All rights reserved.