Ultrasound assisted synthesis of hybrid quinoline-imidazole derivatives: a green synthetic approach

A green, straightforward and efficient study for obtaining hybrid quinoline-imidazole derivatives under ultrasound (US) irradiation as well as under conventional thermal heating (TH) has been presented. The reaction pathway involves only two steps: the N-alkylation of imidazole ring and a Huisgen [3 + 2] dipolar cycloaddition reaction of ylides to dimethyl acetylenedicarboxylate (DMAD). For both types of reactions, a green workup procedure under US irradiation has been presented. Under US irradiation, the N-alkylation of nitrogen atoms from the imidazole nucleus has outstanding benefits in terms of reaction time, energy consumption and yields, and can thereby be considered an environmentally friendly method. Forty new hybrid quinoline-imidazole compounds have been synthesized: 18 salts, 8 dihydro-benzopyrrolo imidazolo quinoline, 9 benzopyrrolo-imidazolo quinoline and 5 dihydro-pyrroloquinoxaline quinoline cycloadducts.

Automated summary

The study demonstrated a green, straightforward, and efficient method for obtaining hybrid quinoline-imidazole derivatives using ultrasound irradiation and conventional thermal heating. The N-alkylation of imidazole ring under ultrasound irradiation showed significant benefits in terms of reaction time, energy consumption, and yields, making it an environmentally friendly method. Forty new compounds were synthesized in this study, including salts, dihydro-benzopyrrolo imidazolo quinoline, benzopyrrolo-imidazolo quinoline, and dihydro-pyrroloquinoxaline quinoline cycloadducts.