DFT study on Ru(II) porphyrin-catalyzed intramolecular amidation of sulfamate esters

Abstract

A DFT calculation was performed to study the potential energy surface of the C-N bond formation reaction of a sulfamate (1) catalyzed by a ruthenium tetrapentafluorophenylporphyrin complex [Ru(TPFPP)(CO), 3]. This reaction is shown in scheme 1.[1] The final amidation product, 2, is the only diastereomer isolated from the reaction system in ref.1. Here we used Ru(por)(CO) (4) to model 3. The imino phenyliodinane (5), could be in situ generated from PhI(OAc)2 and 1. The complex between 4 and 5 is the metal-phenyliodinane complex (6), which could be easily decomposed to a metal-nitrene complex (7) and phenyl iodide. N atom insertion into the C-H bonds on C6 and C7 sites in 7 produces different six-membered ring products in different diastereomers. By calculation of twelve possible reaction pathways, we found a pathway that produces the diastereomer 2 has the lowest reaction energy barrier. This is in good agreement with the experimental results. The reaction mechanism was therefore proposed.

[1] J. L. Liang, S. X. Yuan, J. S. Huang, W. Y. Yu, C. M. Che, Angew. Chem. Int. Ed. 2002, 41, 3465.