•The synthesis of furo[2,3-d]pyrimidines under catalyst-free conditions has been reported.•The green and high efficiency makes this methodology more meaningful.•The present protocol offers direct and facile access to furo[2,3-d]pyrimidine derivatives.A series of furo[2,3-d]pyrimidine derivatives were synthesized via the [3+2] cyclization of pyrimidine-4,6-diol and a variety of nitroolefins at catalyst-free conditions. The reaction is easy to perform simply mixing inexpensive starting materials in water under conventional heating at 90 °C. The reaction proceeds at a fast speed within 1.5–2 h and gives the high biological and pharmacological active substituent furo[2,3-d]pyrimidine derivatives with good to high yields. Mechanism of formation of these furo[2,3-d]pyrimidine derivatives are also proposed.Download high-res image (38KB)Download full-size image

•A domino method has been developed using sulfonic organic resin as catalyst.•The unique feature of solid acid makes the formation of pyranopyrazolopyridines.•The catalyst exhibits good catalytic activity in recyclability study.•The domino reaction follows the acid-catalyzed mechanism.An efficient domino approach for the synthesis of new pyrano[4,3-b]pyrazolo[4,3-e]pyridin-5(1H)-one derivatives has been developed using reusable sulfonic organic resin as catalyst in water. The unique feature of sulfonic organic resin makes the formation of pyrano[4,3-b]pyrazolo[4,3-e] pyridin-5(1H)-ones be possible, and avoids generating ring opening products. The plausible mechanism for this domino reaction is proposed.Download high-res image (94KB)Download full-size image

A series of pyrrolo[2,3,4-kl]acridin-1-one derivatives were successfully synthesized from facile materials (enaminone and isatin) using a reusable solid acid as catalyst in water. A variety of structurally diverse enaminones and various isatins bearing different functional groups tolerated the reaction and gave the corresponding goal products with good to excellent yields. Advantages of this strategy include the mild conditions, operational simplicity, being convenient and environmentally benign, and the reusability of the heterogeneous catalyst. A mechanism was proposed to explain the formation of different substituted pyrrolo[2,3,4-kl]acridin-1-one derivatives.

A simple and efficient procedure for the synthesis of pyrazoloisoquinoline and pyrazolopyridine derivatives by one-pot three-component condensation of aminopyrazoles, aldehydes, and cycloketones in water using carbonaceous material as solid acid catalyst is described. The procedure offers several advantages such as simple experimental and work-up procedures, high yield, recovery, and reusability of metal-free solid acid heterogeneous catalyst along with tolerance of a wide range of functional groups.

Treatment of nitroolefins and o-phenylenediamine with silica gel catalyst produced quinoxalines mainly in THF, but gave benzimidazoles efficiently in water. Such a solvent-dependent chemoselective reaction has prominent features of affording two cyclized products selectively with the same substrate, short reaction time, operational simplicity, as well as available starting materials and nontoxic catalysts. In addition, the scope and limitations were explored and a plausible reaction mechanism is proposed.

•A novel, mild, and environ friendly, one pot synthetic protocol was developed.•The carbonaceous material is first used in domino reaction of nitrostyrene.•The catalyst is reusable and gives high conversions.•The domino reaction follows the acid-catalyzed mechanism.An efficient, high yielding method has been developed for the synthesis of diversity tetrahydro-4H-indol-4-one derivatives via a three component, one pot domino reaction from cyclohexane-1,3-diones, amines and nitrostyrenes using carbon functionalized with sulfonic acid group carbonaceous material as catalyst for the first time. The reaction was carried out in water, affording good to excellent yields in short time. The advantages of atom and step economy, green, and scope make this reaction a powerful tool for assembling heterocyclic scaffolds of general chemical and biomedical interest.Download high-res image (169KB)Download full-size image