A green, catalyst-free synthesis of pyrazolopyranopyrimidines in polyethylene glycol as a biodegradable medium at ambient temperature

Green Synthesis of Pyrazolo Pyrano Pyrimidine Derivatives Using ZnFe2O4/GA as a New Effective Catalyst in Water Media

“…Eventually an intermolecular cyclization and removing the water, led to the intended product. [33] The efficiency of ZnFe 2 O 4 /GA was compared with other catalysts in the synthesis of pyrazolopyranopyrimidines. The results were collected in Table 2.…”

Importance of Hybrid Catalysts toward the Synthesis of 5H-Pyrano[2,3-d]pyrimidine-2-ones/2,4-diones (Thiones)

“…The novel pyrazolopyranopyrimidine 159 and its diverse analogues were synthesized under catalyst-free conditions. For this purpose, Bakherad and co-workers, 193 Kardooni and Kiasat, 186 and Rathinam et al 194 carried out a three-component equimolar reaction of 1 , 11 / 11a , 12c , and 28 under catalyst-free conditions in 4 mL of magnetized water at 50 °C, PEG-400 (3 mL) at RT, and 2 mL of aqueous EtOH at 80 °C ( Scheme 107 ). In Method 1, the magnetized water used here was prepared using a static magnetic system with a field strength of 6000 G with 500 mL s –1 for up to 10 min.…”

Recent advancements in the multicomponent synthesis of heterocycles integrated with a pyrano[2,3-d]pyrimidine core

“…The amphoteric properties of L-proline enable the activation of the oxygen atom of carbonyl group, and hydrogen atom of the NH group by hydrogen bond formation with hydrogen atoms of acidic and basic groups, respectively. 106 Aher et al 107 have modied the synthesis of the previously reported, 3-methyl-4-aryl-4,8-dihydropyrazolo[4 0 ,3 0 :5,6]pyrano [2,3-d]pyrimidine-5,7(1H,6H)-diones, 108,109 with excellent yields (85-96%) through solvent-free four-component one-pot reactions of barbituric acid, hydrazine, aryl aldehydes, and ethyl acetoacetate using tungsten-substituted molybdo-phosphoric acids, H 3 [PMo 7 W 5 O 40 ]$24H 2 O as a catalyst. The Keggin-type catalyst activated oxygen atoms of carbonyl groups for condensation steps to construct pyrazole ring, Knoevenagel condensation of the aldehyde with barbituric acid, and pyran ring cyclization.…”

“…The Keggin-type catalyst activated oxygen atoms of carbonyl groups for condensation steps to construct pyrazole ring, Knoevenagel condensation of the aldehyde with barbituric acid, and pyran ring cyclization. 107 Keshavarz et al 110 have progressed a green protocol for the synthesis of the previously reported tricyclic systems 32, 104,108,[111][112][113] using a recyclable heterogeneous organicinorganic hybrid durable nano-catalyst "g-Al 2 O 3 @silane-TMG" (Scheme 21). Thus, four-component one-pot reactions of hydrazine, ethyl acetoacetate, (thio)barbituric acid, and aryl aldehydes in water under gently heating (40 C), and catalytic conditions gave the anticipated products 32 in 85-98% yields.…”

“…Keshavarz et al 110 have progressed a green protocol for the synthesis of the previously reported tricyclic systems 32 , 104,108,111–113 using a recyclable heterogeneous organic-inorganic hybrid durable nano-catalyst “γ-Al 2 O 3 @silane-TMG” (Scheme 21). Thus, four-component one-pot reactions of hydrazine, ethyl acetoacetate, (thio)barbituric acid, and aryl aldehydes in water under gently heating (40 °C), and catalytic conditions gave the anticipated products 32 in 85–98% yields.…”