Application of beta-(2-chloroaroyl)thioacetanilide in synthesis(III): an efficient three-component synthesis of thiochromeno[2,3-b]pyridines catalyzed by KF/neutral Al2O3 co-operated with PEG 6000 under microwave irradiation.

A series of new functionalized thiochromeno[2,3-b]pyridine derivatives have been synthesized via a sequence of Knoevenagel condensation, Michael addition, cyclization, and intramolecular nucleophilic substitution, which is first catalyzed by KF/neutral Al(2)O(3) cooperated with PEG 6000 under microwave irradiation. Experimental results indicated that among the catalysts tested, KF/ neutral Al(2)O(3) with PEG 6000 exhibits the best catalytic activity, which leads to a substantial improvement in the overall yield and purity of the desired final products and significantly shorter reaction time.