Catalysis and mechanistic studies of ruthenium and osmium on synthesis of anthranilic acids

Abstract

AbstractRuthenium, osmium and ruthenium + osmium catalyzed synthetic methodology was developed for the synthesis of anthranilic acids from indoles in good to excellent yields using bromamine‐B in alkaline acetonitrile–water (1:1) at 313 K. Detailed catalysis studies of ruthenium, osmium and the mixture of both were carried out for the synthetic reactions. The positive synergistic catalytic activity of Ru(III) + Os(VIII) was observed to a large extent with the activity greater than the sum of their separate catalytic activities. Detailed kinetic and mechanistic investigations for each catalyzed reactions were carried out. The kinetic pattern and mechanistic picture of each catalyzed reaction were found to be different for each catalyst and to obey the underlying rate laws: where, x, y < 1. The reactions were studied at different temperatures and the activation parameters were evaluated for each catalyzed reaction. Under the identical set of experimental conditions, the kinetics of all the three catalyzed reactions were compared with uncatalyzed reactions, revealing that the catalyzed reactions were 6‐ to 42‐fold faster. The catalytic efficiency of aforementioned catalysts followed the order: Ru(III) + Os(VIII) > Os(VIII) > Ru(III). This trend may be attributed to the different d‐electronic configuration of the catalysts. The proposed mechanisms and the rigorous kinetic models derived give results that fit well with the experimental data in each catalyzed reaction. Copyright © 2010 John Wiley & Sons, Ltd.