A new approach for the synthesis of 3,4-dihydropyrano[c]chromenes and biscoumarins using {[2,2’-BPyH][C(CN)3]2} as a bifunctional nanostructured ionic liquid catalyst

Abstract

[2,2'-Bipyridine]-1,1'-diium tricyanomethanide {[2,2'-BPyH][C(CN)3]2} as a bifunctional nanostructured ionic liquid catalyst (0.5 mol%) was used for the synthesis of 3,4-dihydropyrano[c]chromenes (14 examples) under solvent-free condition at room temperature in high yield (82-91%) and short reaction time. In addition, the described ionic liquid catalyst was also applied for the synthesis of biscoumarins (8 examples) under the same reaction condition in good yield (87-91%) and short reaction time. The {[2,2'-BPyH][C(CN)3]2} was attained by the reaction of 2,2'-Bipyridine (5 mmol) and 5 mL an aqueous solution of tricyanomethane (5 mmol) at room temperature for 3 hours. The {[2,2'-BPyH][C(CN)3]2} was obtained with high purity that was approved by FTIR, 1H NMR, 13C NMR, mass, TG, DTA, XRD, SEM, TEM analysis and melting-point determination. The catalyst was recovered in excellent yield and was used in the revealed reaction 5 times without the need of additional catalyst. The major advantages of the presented procedure are efficient catalysis and good cost efficiency.