This study investigated the existence of keto-enol tautomers for the first time during the synthesis of aryl-bis(2-hydroxy-1-naphthyl)methane from 2-naphthol and p-tolualdehyde or 4-chlorobenzaldehyde in methanol using CuSO4.5H2O as catalyst under reflux condition. The exclusive formation of aryl-bis(2-hydroxy-1-naphthyl)methanes was observed in dichloromethane at room temperature in the presence of BF3.OEt2/AcOH as catalyst. The keto products were isolated and characterized by 1H NMR, 13C NMR, COSY and DEPT spectra. The existence of keto tautomer (3) of aryl-bis (2-hydroxy-1-naphthyl)methanes (4) was identified in the reaction of 2-napthol with p-tolualdehyde and 4-chlorobenzaldehyde using CuSO4.5H2O as catalyst under reflux in methanol. Exclusive formations of (4) was observed at mild conditions in dichloromethane with BF3.OEt2/AcOH as catalyst.