Chemoselective and one-pot synthesis of novel coumarin-based cyclopenta[c]pyrans via base-mediated reaction of α,β-unsaturated coumarins and β-ketodinitriles

In this paper, the base-mediated cascade reactions of 4-chloro-3-vinyl coumarins with β-ketodinitriles were demonstrated, allowing the efficient synthesis of coumarin-based cyclopenta[c]pyran-7-carbonitriles with interesting chemoselectivity. These transformations include the domino-style formation of C–C/C–C/C–O bonds through a base-mediated nucleophilic substitution, Michael addition, tautomerization, O-cyclization, elimination, and aromatization. The presented synthetic strategy has many advantages such as simple and readily available starting materials, green solvent, highly chemoselective route, synthetically useful yields, and easy purification of products by washing them with EtOH (96%), described as GAP (Group-Assistant-Purification) chemistry.