Regioselective Synthesis of New Aryloyl-Functional Thiazolo[3,2-a]pyridine Using Ketene Dithioacetals in Ethanol Media

Thiazolo[3,2-a]pyridines are well known as an important class of sulfur-nitrogen containing heterocycles with two different fused heterocycles, which are found in a broad range of compounds possessing a variety of biological activities such as potent CDK2-cyclin A inhibitor, potential uterus stimulant, beta-amyloid production inhibitor,coronary dilator, antibacterial, antifungal, scavenge free radicals because of possessing electron acceptors and donors, and also these derivatives play an important role in drug development for chemotherapy of various cancers [1, 2]. We report a novel approach to prepare a series of heterocycles containing thiazole and pyridine rings which substituted with nitro and aryloyl groups. The title compounds are obtained from one-pot four-component reaction of nitroketene dithioacetals, cysteamine hydrochloride, dimedone and phenylglyoxal in ethanol (Scheme 1). These sulfur-nitrogen containing heterocycles with drug potential activity, synthesized through sequential Knoevenagel/Michael/intramolecular Ncyclization sequences. Environmentally benign procedure without the use of any catalyst or metal promoters, mild reaction conditions, easy work-up with superior atom economy are some advantages of this method.