Diphenhydramine Hydrochloride–CuCl as a New Catalyst for the Synthesis of Tetrahydrocinnolin-5(1H)-ones

Abstract

The current study deals with the synthesis and characterization of a novel catalyst made from diphenhydramine hydrochloride and CuCl ([HDPH]Cl−CuCl). The prepared catalyst was thoroughly characterized using various techniques, such as 1 H NMR, Fourier transform-infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis and derivative thermogravimetry. More importantly, the observed hydrogen bond between the components was proven experimentally. The activity of this catalyst was checked in the preparation of some new derivatives of tetrahydrocinnolin-5(1H)ones via a multicomponent reaction between dimedone, aromatic aldehydes, and aryl/alkyl hydrazines in ethanol as a green solvent. Also, for the first time, this new homogeneous catalytic system was effectively used for the preparation of unsymmetric tetrahydrocinnolin-5(1H)-one derivatives as well as mono-and bis-tetrahydrocinnolin-5(1H)-ones from two different aryl aldehydes and dialdehydes, respectively. The effectiveness of this catalyst was further confirmed by the preparation of compounds containing both tetrahydrocinnolin-5(1H)one and benzimidazole moieties from dialdehydes. The one-pot operation, mild conditions, rapid reaction, and high atom economy, along with the recyclability and reusability of the catalyst, are other notable features of this approach.

Efficient synthesis of novel thiadiazolo[2,3-b]quinazolin-6-ones catalyzed by diphenhydramine hydrochloride-CoCl2⋅6H2O deep eutectic solvent

“…The peaks at 4.70, 4.54, and 4.27 ppm are related to H 3 , H 2 , and H 1 , respectively. Surprisingly, All the mentioned peaks are down-fielded compared to the similar peaks in the [HDPH]Cl spectrum 50 . Also, the characteristic peak corresponding to –N + –H in 2[HDPH]:CoCl 4 2− shifted from 12.58 to 13.21 ppm and becomes wider (Fig.…”

“…In the FT-IR spectrum of CoCl 2 ·6H 2 O, the broad bands at 3500 and 1598 cm −1 are related to the vibrational modes of surface water 19 . In the spectra of [HDPH]Cl 50 and [HDPH]:CoCl 4 2− , the specific bands were observed at 3029 cm −1 (sp 2 C–H) and 1111 cm −1 (C–O–C). The characteristic bands at 1454 and 1386 cm −1 are related to CH 2 and CH 3 stretching vibrations, respectively.…”

“…6 a), the characteristic band at 1446 cm −1 , indicates that 2[HDPH]:CoCl 4 2− has Lewis acidic sites which interact with pyridine groups. Also, the band appeared at 1635 cm −1 in the FT-IR spectrum of pyridine-2[HDPH]:CoCl 4 2− could be attributed to the formation of pyridinium ions ([PyH] + ) upon the interaction of pyridine with Brønsted acid sites of the LA-DES 3 , 50 . Such an interaction has been displayed in Fig.…”

“…To introduce the existing method as an eco-friendly and green synthetic path for the preparation of thiadiazolo[2,3-b]quinazolin-6-one scaffolds, a number of green metric factors 50 , 53 – 56 were calculated for the synthesized compounds (Figs. 15 and 16 ).…”