“…A plethora of review reports are there on the synthesis of dihydropyrano coumarin derivatives via one pot reaction of aromatic malononitrile, aldehydes and CÀ H active acids in the presence of homogeneous or heterogeneous catalysts such as organic acids or bases, nanoparticles, zeolites, and Ionic liquids. [25][26][27] Numerous catalysts such as 1,4diazabicyclo[2.2.2]octane (DABCO), [11] ammonium acetate, [28] 1,8diazabicyclo[5.4.0]undec-7-ene (DBU), [29] urea, [30] piperzine, [31] triethylbenzylammoniumchloride (TEBA), [32] diammonium hydrogen phosphate, [33] piperidine, [34] ammonium/sodium formate, [35] 2-hydroxyethylammonium formate, [36] CuO, [37] sodium tungstate, [38] Fe 2 O 3 , [39] GN/SO 3 H, [40] oxo-vanadium phthalocyanine, [41] Ti 2 O, [42] cobalt orthophosphate (Co 3 (PO 4 ) 2 ), [43] tert-butyl hydrogen peroxide, [44] cyclodextrin, [45] 1-butyl-3-methylimidazolium triflate [46] and many more have been reported for the synthesis of dihydropyrano coumarins. Yousefi et al prepared pyranocoumarins by employing piperzine as a catalyst (Scheme 1a).…”