Rare earth perfluorooctanoate [RE(PFO)3] catalyzed one-pot synthesis of benzopyran derivatives

Grindstone Chemistry: An Efficient and Green Synthesis of 2-Amino-4H-benzo[b]pyrans

“…The conventional reported synthesis of 4H-pyran derivatives uses piperidine and triethylamine in organic solvents. A variety of other reagents such as HMTAB [22], TEBA, Re(PFO) 3 [23], NaBr [24], S-proline [25], L-proline [26] the use of microwave irradiation [27], infrared radiation [28], KF-basic alumina in dimethylformamide (DMF) [29], ultrasound irradiation [30], aminofunctionalized ionic liquids [31], SBA-15 mesoporous silica [32], silica nanoparticals [33] and ammonium acetate under microwave irradiation [34] were found to catalyze this reaction. Most of the mentioned methods have at least one of the limitations such as low yield, long reaction times, effluent pollution, harsh reaction conditions, formation of by-products, the use of toxic organic solvents, the use of additional instruments such as ultra sound and tedious workup procedures.…”

An expeditious and greener one-pot synthesis of 4H-chromenes catalyzed by Ba(OTf)2in PEG-water

“…for several hours (28Á31). In recent years new method have been developed for the synthesis of 4H-chromene-3-carbonitrile derivatives using various reagents such as d,l-proline (32,33), MgO (34,35), rare-earth perfluorooctanoate (36), ammonium salts (37Á42), DBSA (43), LiBr (44), CeCl 3 ×H 2 O (45), potassium phosphate (46), and different energy sources such as microwave-irradiation (47,48) and ultrasonic irradiation (49,50). Recently, a catalyst free method was reported for the synthesis of 4-pyrazolyl-4H-chromene derivatives in water (51).…”

A facile, one‐pot, green synthesis of polysubstituted 4H‐pyrans via piperidine‐catalyzed three‐component condensation in aqueous medium

“…Polysubstituted 4H-pyrans as an important class of heterocyclic components present in many natural or synthetic compounds with important biological or pharmacological activities such as antibacterial [9], anticancer [10], and antiallergic [11]. Many methods such as ionic liquid [12], solid base [13], Lewis acid [14,15], and electrochemistry [16] have been used to synthesize polysubstituted 4H-pyrans, but a lot of methods use volatile and toxic organic solvents, which are the major pollution source in chemical industry.…”