Microwave-assisted Synthesis of Pharmacologically Active 4-Phenoxyquinolines and their Benzazole-quinoline Hybrids Through SNAr Reaction of 4,7-dichloroquinoline and Phenols Using [bmim][PF6] as a Green Solvent.

Abstract

Quinoline and its derivatives have been shown to display a wide spectrum of biological properties, especially anticancer activity. Particularly, diverse potent anticancer drugs are based on the 4-phenoxyquinoline skeleton, acting as small-molecules VEGR2 and/or c-Met kinase inhibitors. However, the design of new drugs based on these quinoline derivatives remains a challenge. Up till now, all approaches to 4-phenoxyquinoline skeleton construction do not obey any green chemistry principles. Developing a new, and efficient protocol for the synthesis of potentially bioactive 4-phenoxyquinoline derivatives and benzazole-quinoline-quinoline hybrids from commercially available 4,7-dichloroquinoline and phenol derivatives using microwave energy (MW) in the presence of 1-methyl 3-butylimidazolium hexafluorophosphate. Neweco-efficient protocol for valuable 7-chloro-4-phenoxyquinolines and their hybrids, which is based on SNAr reaction of 4,7-dichloroquinoline with respective simple phenols and hydroxyaryl- benzazoles under MWenergy in green reaction media, is studied for the first time. We found that among various solvents tested, the ionic liquid 1-methyl 3-butylimidazolium hexafluorophosphate ([bmim][PF6]) favored the SNAr reaction affording phenoxyquinolines in excellent yields (72-82%) in 10 min. The developed protocol allowed to obtain quickly in good yields (48-60%) new diverse benzazole-quinoline hybrids, which are expected to be pharmacologically active. According to the calculated bioactivity scores, new hybrids are potential kinase inhibitors that could be useful in anticancer drug research. We developed for the first time a new green, efficient method to prepare potentially bioactive functionalized 7-chloro-4-phenoxyquinolines and benzazole-quinoline molecules. Good to excellent yields of the quinoline products, use of MW irradiation in ([bmim] [PF6] as a green solvent, and short times of reactions are some of the main advantages of this new protocol.