Research Article

Pentafluoropropionic Acid: An Efficient and Metal-Free Catalyst for the One-Pot Synthesis of Tetrahydrobenzo[b]pyran Derivatives

Table 2

Synthesis of tetrahydrobenzo[b]pyrans using pentafluoropropionic acid as catalysta.

EntryArProductbTime (min)Yield (%)cm.p., (°C) [reference]

1C6H54a8090227–229 [28]
23-NO2C6H44b8089207–210 [28]
34-MeOC6H44c6090197–199 [22]
44-MeC6H44d6092216–218 [13]
54-BrC6H44e6090206–208 [10]
63-MeOC6H44f8090207–209 [—]
73-ClC6H44g8089223–224 [13]
84-ClC6H44h6092213–215 [11]
9 2-ClC6H44i8089203–205 [14]
104-HOC6H44j8090206–208 [22]

Aromatic aldehyde (1 mmol), dimedone (1 mmol), malononitrile (1.2 mmol), and PFPA (35 mol%) in the mixture of EtOH : H2O (1 : 1).
bThe products were characterized by comparison of their spectroscopic and physical data with those reported in the literature.
cIsolated yield.