An efficient studies on C-2 cyanomethylation of the indole synthesis: the electronic and spectroscopic characterization (FT-IR, NMR, UV-Vis), antioxidant activity, and theoretical calculations

Abstract

The direct cynamethylation with the development of catalyzed methodologies directed to 2-(cyanomethyl)indoles was reported by using tetrafluoro-1,4-benzoquinone (TFB) as the catalyst and it was synthesized in one step without protecting the indole N-H. Due to the plenty of synthesis indole moieties is currently the object of extensive investigations due to their biologically interesting role as the recognized block in many natural products and bioactive products. Moreover, the desired products were achieved in good yields. The antioxidant activity of the intermediates and the final product was explored by the DPPH method, and the results disclosed that the intermediate R2a and the final product could be used as promising agents in biomedicinal research. The structural and physicochemical properties of the intermediate and product indoles were enlightened by DFT calculations at B3LYP/6-311G(d,p) level, in the gas, CHCl3, methanol, and water environments. The TD-DFT calculations at the same level of theory were performed to compare with the recorded spectra of the studied compounds and to illuminate the possible electronic transitions (s(0) > s(n)) underlying the observed peaks. The NBO analyses of the compounds indicated that the n -> pi* and pi -> pi* interactions were a great portion of the lowering of the stabilization energy. The FMO analyses displayed that the intermediates and product, but the intermediate R2a mostly in all solvents, tended the electrodonating capability to the external molecular system. (C) 2021 Elsevier B.V. All rights reserved.