DFT study of the mechanism of Cu(I)-catalyzed and uncatalyzed intramolecular cyclopropanation of iodonium ylides

The mechanism of the Cu(I)-catalyzed and uncatalyzed intramolecular cyclopropanation of ketoesteric and diesteric iodonium ylides has been thoroughly explored by means of electronic structure calculation methods (DFT). All crucial reaction steps encapsulated in the entire catalyzed and uncatalyzed reaction pathways were scrutinized, while the elementary steps, the intermediates and transition states were identified through monitoring the geometric and energetic reaction profiles. It was found that CuCl efficiently catalyze the cyclopropanation of iodonium ylides only for their diesteric derivatives and their diazo analogues via stabilization of the respective carbene upon complexation with the metal center. For the ketoesteric iodonium ylides the CuCl catalyst does not affect the kinetics of the intramolecular cyclopropanation reactions which could proceed easily without the catalyst, in line with available experimental observations. (C) 2010 Elsevier B. V. All rights reserved.