An Efficient, High Yielding Protocol for the Synthesis of Functionalized Quinolines via the Tandem Addition/Annulation Reaction of O-Aminoaryl Ketones with α-Methylene Ketones

Abstract

Quinolines are well known for a wide range of medicinal properties being used as antimalarial, antiasthmatic, antihypertensive, antibacterial and tyrosine kinase inhibiting agents [1]. They are also applied for the preparation of nano and meso structures having enhanced electronic and photonic properties [2]. Thus, the synthesis of quinolines is an important and useful task in organic chemistry. The Friedlander annulation is a straight forward synthesis of these compounds [3]. This method involves the acid or base catalyzed or thermal condensation between α-2-aminoaryl ketone and another carbonyl compound possessing a reactive α- methylene group followed by cyclodehydration. We recently observed that CaFe2O4@SiO2@SO3H catalyzes the synthesis of quinolines under mild conditions (Fig. 1). Initial research was focused on the reaction between α-2-aminoaryl ketone and another carbonyl compound possessing a reactive α-methylene group followed by cyclodehydration and different solvents and different amounts of the catalyst were tested to find the optimized conditions. The easy removal of the catalyst makes this method a suitable choice for the synthesis of new biologically active compounds. A simple process, short reaction time, green condition, availability and use of inexpensive reagents make the procedure novel and unique. High yields (75-96%) are other advantages of our method.