Cyanomethylation of 2,3,4,9-tetrahydro-1H-carbazol-1-one based on using two different reagents: Antioxidant activity and DFT studies

Abstract

C-2 and C-6 monoalkyl nitrile substituted reactant (1) , which constitute the tricyclic framework of car- bazole derivatives along with the substructure of the Strychnos alkaloids family, have been synthesized by using different bases to produce substitution reactions. In addition, the antioxidant capacity of the synthesized compound by the CUPRAC (cupric reducing antioxidant capacity) method was evaluated and the obtained TEAC (Trolox equivalent antioxidant capacity) coefficient implied that product (2) has an- tioxidant feature. The B3LYP/6-311G(d,p) level calculations were performed in the gas phase, and the optimized geometries obtained from these calculations were used for the solvation media calculations. The SMD variation of the IEFPCM (polarized continuum model) was used to conduct the quantum chem- ical calculations in the solvent environment such as CHCl 3 , CH 3 OH, and H 2 O (water, ε= 78.4). Also, the NMR chemical shifts of the products were calculated using GIAO (Gauge-Independent Atomic Orbital) ap- proach and compared with the corresponding experimental data. The TD-DFT calculations disclosed that the observed peaks for both products were attributed to the n → π∗and π→ π∗excitations. Moreover, NBO analysis revealed that the n → π∗and π→ π∗interactions have a great importance for lowering the stabilization energy for all compounds. Also, the FMO (Frontier Moleular Orbital) analyses implied that the product P2 would prefer the intermolecular interactions would rather than the intramolecular interactions.