Combined Kinetic, and Theoretical Approaches for the Study of the SEAr Reactions of 2-(2’,4’,6’-trinitrophenyl)-4,6-dinitrobenzotriazole 1-oxide with 5-R-substituted Indoles in Acetonitrile

Abstract

Abstract We present a kinetic and theoretical study of nucleophilic addition reactions involving 2-(2’,4’,6’-trinitrophenyl)-4,6-dinitrobenzotriazole 1-oxide 1 with a series of 5-R-substituted indoles 2a-e (R = CN, Cl, H, Me and NH2) in acetonitrile at 20°C. Single electron transfer (SET) mechanism was proposed and confirmed by the agreement between the rate constants (k) and the oxidation potentials (Epox) of these series of indoles. Using Mayr's equation, the electrophilicity parameter (E) of 1 at C-7 position is derived and compared with the same parameter estimate using empirical equation E vs. pKa. Density Functional Theory (DFT) calculations were performed to confirm the suggested reaction mechanisms and elucidate the origin of the electrophilic reactivity of 1. Notably, a linear correlation (R2 = 0.9957) between the experimental nucleophilicity (N) and the theoretical model of nucleophilicity (ω−1) determined in this work of various 5-R-substituted indoles has been obtained and discussed.