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

Abstract

Pentafluoropropionic acid (PFPA) efficiently catalyzes the one-pot, three-component reaction of aromatic aldehyde, malononitrile, and dimedone to yield tetrahydrobenzo[b]pyran derivatives in high yields. This method is of great value because of its easy processing, short reaction time, environmentally, and high yields.

Fe3O4@RB@LDH: Efficient and Recyclable Photocatalyst Visible‐Light Mediated Synthesis of Pyran and Pyrrolidinone Derivatives and Their Anti‐Microbial Activities

“…[24] Aq. EtOH, reflux Upto 94 % 60-150 min No 4 4H-benzo[b]pyran SiO 2 @Pr@SO 3 H, [25] H 2 O, reflux Upto 98 % 15-35 min Yes 5 4H-benzo[b]pyran PFPA, [28] H 2 O-EtOH, RT Upto 92 60-80 min No 6 4H-benzo[b]pyran Fe 2 O 3 @SiO 2 @VB 1 NPs, [29] Aq. ETOH (4 : 1), US, 50-80 °C Upto93 % 6 hrs ( 360 min) Yes 7 4H-benzo[b]pyran molecular iodine, [30] DMSO, heat at 120 °C Upto 92 % 3-4 h No 8 4H-benzo[b]pyran LiBr, [31] H Pyrazolopyran Cl 3 CCOOH, [26] Solvent-free, 100 °C Upto 98 % 3-9 min No 11 Pyrazolopyran NaF, [33] H 2 O, RT Upto 98 % 5-10 min No 12 Pyrazolopyran Et 3 N, [52] EtOH, 50 Pyrrolidinone Fe 3 O 4 @SiO 2 @Propyl-ANDSA, [40] EtOH, RT Upto 98 % 8 h Yes 19…”

“…Therefore, good efforts have been made by chemists for the synthesis of these heterocyclic scaffolds using numerous methodologies. A number of methods have been reported for the synthesis of pyran detivatives involving the multicomponent condensation of aldehydes, malononitrile and 1,3 cyclic diketones or substituted pyrazoles in presence of various catalysts such as (NH 4 ) 2 HPO 4 , [22] Na 2 SeO 4 , [23] CeCl 2 .7H 2 O, [24] SiO 2 @Pr@SO 3 H, [25] Cl 3 COOOH, [26] sodium acetate, [27] PFPA, [28] Fe 2 O 3 @SiO 2 @VB 1 NPs, [29] molecular iodine, [30] LiBr, [31] pyridinium p-toluenesulfonate, [32] NaF, [33] etc. In spite of the advantages of these synthetic methods, quite a few of them have some limitations such as harmful conditions, expensive catalyst, low yields, long reaction times, high temperature, difficult workup procedure etc.…”

Quaternary Vanado‐Molybdotungstophosphoric Acid [H5PW6Mo4V2O40] Over Natural Montmorillonite as a Heterogeneous Catalyst for the Synthesis 4H‐Pyran and Polyhydroquinoline Derivatives

“…[35][36][37][38] The tetrahydrobenzo[b]pyrans moiety forms the essential fragment of many biologically active compounds and their importance has been investigated comprehensively, such as anticancer, anticoagulation, spasmolytic, antibacterial, antianaphylactic activity, and diuretic properties. [39] There are many synthetic methods for the synthesis of tetrahydrobenzo [b] pyrans derivatives is a three-component reaction of aryl aldehydes, cyclic 1,3-diketonesand malononitrile in the presence of various catalysts and solvents, [40] such as Amberlite IRA-40, [41] hexadecyl dimethyl benzyl ammonium bromide, [42] Pentafluoropropionic Acid, [43] tetrabutylammonium bromide (TBAB), [44] sodium selenite, [45] ionic liquid, [46,47] ZnO-Zeolite and nanoparticles. [48,49] Some of these protocols have their own merits and demerits, such as modest yields, long reaction times, harsh reaction conditions, tedious workup leading to the generation of large amounts of toxic waste and non-reusability of the catalyst.…”