One-Pot Synthesis of Tetrahydrobenzo[b]pyran Derivatives Catalyzed by Amines in Aqueous Media

A facile and efficient synthesis of 2-amino-3-cyano-4H-chromenes and tetrahydrobenzo[b]pyrans using 2,2,2-trifluoroethanol as a metal-free and reusable medium

“…Pyran annulated heterocyle derivatives represent an important class of oxygen-containing heterocycles being the main components of many natural occurring products, and are widely employed as cosmetics, pigments [1], and potential biodegradable agrochemicals [2] and exhibit a wide spectrum of biological activities [3][4][5][6][7][8][9][10][11][12]. 4H-Pyran can also serve as useful building blocks in the generation of a variety of natural products showing molluscicidal, antibacterial, anticancer, antitubercular, antimicrobial, anti-coagulant, antiallergic, antibiotic, hypolipidemic, and immunomodulating activities [13][14][15][16][17][18][19][20].…”

Silica-coated magnetic NiFe2O4 nanoparticles-supported H3PW12O40; synthesis, preparation, and application as an efficient, magnetic, green catalyst for one-pot synthesis of tetrahydrobenzo[b]pyran and pyrano[2,3-c]pyrazole derivatives

“…Catalysts used for one-pot, three-component reactions include piperidine [21], hexadecyltrimethyl ammonium bromide (HTMAB) [22], sodium bromide [23], ionic liquids [24][25][26][27][28][29], tetramethylammonium hydroxide [30], diammonium hydrogen phosphate [31], organocatalysts [32], sodium selenite [33], tetrabutylammonium bromide (TBAB) [34,35], polyaniline-silica gel [36], alum [KAl(SO 4 ) 2 Á12H 2 O] [37], rare earth perfluorooctanoates, e.g. Re(PFO) 3 [38], Caro's acid [39], amines or amino acids [40], potassium phosphate [41], PPA-SiO 2 [42], microwave irradiation [43], BF 3 ÁOEt 2 [44], magnetic core-shell titanium dioxide nanoparticles (Fe 3 O 4 @SiO 2 @TiO 2 ) [45], NH 4 H 2 PO 4 -Al 2 O 3 [46], DABCO-EtOH [47], TPPA [48], t-BuOK-t-BuOH [49], L-proline under ultrasound irradiation [50], and silica coated magnetitepolyoxometalate nanoparticles (Fe 3 O 4 @SiO 2 @NH-NH 2 -H 3 PW 12 O 40 ) [51]. Many of these methods suffer from one or more limitations, for example low yields, use of expensive reagents, long reaction times, tedious work-up procedures, and cooccurrence of several side reactions.…”

Snail shell as a new natural and reusable catalyst for synthesis of 4H-Pyrans derivatives

“…[12][13][14] Many of the methods for the synthesis of 4H-pyrans are reported in the literature. [15][16][17][18][19][20][21] Although, these methods have their own merits, they still have significant limitations like harsh reaction conditions, low yields, long times reactions and use of synthetic catalysts. These findings stimulated our interest to develop new simple, efficient and green process for the synthesis of these ring systems derivatives.…”