Reaction mechanism and stereoselectivity of ruthenium--porphyrin-catalyzed intramolecular amidation of sulfamate ester: a DFT computational study.

The reaction mechanism of the ruthenium--porhyrin complex [Ru(por)(CO)]-catalyzed intramolecular C-H bond amidation was examined using density functional theory (DFT) calculations. The metal-nitrene reactive intermediate, Ru(por)(CO)-NSO3R1 (R1 = 1-methylclohexl-methyl) was found to be highly favorable to generate in terms of the free energy profile from the reaction of the starting materials. Ru(por)(CO)-NSO3R1 may exist in both singlet and triplet states since they are close in energy. In each state, six C-H bond amidation reaction pathways were characterized structurally and energetically. The predicted most probable diastereomeric product out of the four possible diasteromeric products examined in the calculations for the amidation reactions agree well with previously reported experimental results.