Polyethylene glycol-promoted synthesis of pyrimido[1,2-a]benzimidazole and pyrano[2,3-c]pyrazole derivatives in water

Synthesis of Metal–Organic Frameworks MIL-101(Cr)-NH2 Containing Phosphorous Acid Functional Groups: Application for the Synthesis of N-Amino-2-pyridone and Pyrano [2,3-c]pyrazole Derivatives via a Cooperative Vinylogous Anomeric-Based Oxidation

“…Also, the absorption bands observed at 1021 and 1081 cm –1 are related to the P–O bond stretching and that at 1146 cm –1 is related to PO . Furthermore, peaks of Cr–O of octahedral CrO 6 appeared at 1391 cm –1 respectively (Figure ). The FT-IR spectrum difference between MIL-101­(Cr)-NH 2 and MIL-101­(Cr)-N­(CH 2 PO 3 H 2 ) 2 confirmed the structure of the catalyst.…”

Dihydroazolopyrimidines: Past, Present and Perspectives in Synthesis, Green Chemistry and Drug Discovery

“…[240] The use of other green catalysts for the synthesis of 1,4dihydrobenzo [4,5]imidazo[1,2-a]pyrimidine-3-carbonitriles has been described; among these are: Brønsted acidic ionic liquid 1-methyl-3-(trimethoxysilylpropyl)-imidazolium hydrogen sulfate supported on rice husk ash (RHA-[pmim]HSO 4 ) under solvent-free conditions, [241] p-toluenesulfonic acid under neat conditions, [242] and silica sulfuric acid in ethylene glycol. [243] Survase and co-authors [244] described the synthesis of pyrimido[1,2-a]benzimidazole derivatives using polyethylene glycol in water (PEG-400) as solvent under catalyst-free conditions in multicomponent reaction of 2-aminobenzimidazole, malononitrile and aromatic aldehyde. Another example of using PEG described for one-pot similar multicomponent reaction of 2-aminobenzoimidazole, various aldehydes and 2cyanoacetamide without adding catalyst at room temperature.…”

Applications of pyrazolone in multicomponent reactions for the synthesis of dihydropyrano[2,3-c]pyrazoles and spiro-pyrano[2,3-c]pyrazoles in an aqueous medium

“…Total 19 compounds were obtained by this method and the yield of the corresponding product 31 and 32 were high ranging from 80-95% and 48-86% respectively. 60 Recently, the combination of PEG and water as a sustainable reaction medium for promoting the multicomponent synthesis of dihydropyrano [2,3-c]pyrazoles has been established by Survase et al 61 The synthesis of several derivatives of dihydropyrano [2,3-c]pyrazoles 37 from aldehydes 10, malononitrile 2, and pyrazolone 16 was first carried out by employing different solvent system including toluene, DMF, DMSO, water, PEG-600 and in different ratio of PEG-water solvent system at room temperature. From the optimized reaction condition, it was found that the PEG-water solvent system was the best choice of reaction medium for the preparation of dihydropyrano [2,3-c]pyrazole derivatives, and products were obtained in good to excellent yield ranging from 80-91% (Scheme 11).…”