An efficient one-pot synthesis of functionalized 2-amino-4H-pyrans by a meglumine-catalyzed three-component reaction has been developed. A broad range of substrates including aromatic and heteroaromatic aldehydes, isatin derivatives, and acenaphthenequinone are condensed with enolizable C–H activated compounds and alkylmalonates to give the desired products in high to excellent yields. This methodology provides an alternative approach for rapid access to construct a diversity-oriented library of 4H-pyrans.

Meglumine: A novel and efficient catalyst for one-pot, three-component combinatorial synthesis of functionalized 2-amino-4H-pyrans.

A simple, efficient and environmentally benign protocol has been developed for the one-pot, multicomponent synthesis of medicinally important tetrahydrobenzo[b]pyrans and pyran-annulated heterocycles using a commercially available, inexpensive, non-toxic, and biodegradable tris-hydroxymethylaminomethane (THAM) as a novel organocatalyst. Ambient reaction conditions, wide scope, avoidance of conventional isolation as well as purification techniques and the reusability of the catalyst for five consecutive runs have improved the practical utility of this multicomponent reaction protocol manifold.

Tris-hydroxymethylaminomethane (THAM): a novel organocatalyst for a environmentally benign synthesis of medicinally important tetrahydrobenzo[b]pyrans and pyran-annulated heterocycles

Fruit juice of Citrus limon (lemon juice) has been utilized as a natural and renewable catalyst for the green and environmentally friendly preparation of 3,4-disubstituted isoxazol-5(4H)-one derivatives and 6-amino-1,4-dihydropyrano[2,3-c]-pyrazole-5-carbonitrile derivatives in hydroalcoholic media at 90 °C. A one-pot three-component reaction of β-oxoesters with hydroxylamine hydrochloride and various aromatic aldehydes afforded 3,4-disubstituted isoxazole-5(4H)-one derivatives in excellent yields. The rate constant (K = 6.12 × 10−2 min−1 at 25 °C) for the formation of isoxazole derivative (1g) was also calculated. Similarly, a four-component reaction of ethyl acetoacetate, hydrazine hydrate, aryl aldehydes, and malononitrile gives pyrano[2,3-c]-pyrazole derivatives in very good yields. After completion of the reaction, the products were isolated by simple filtration. A simple work-up process, high product yields, short reaction times, and the use of an inexpensive and biodegradable catalyst are the advanced rewards of the present protocol.

Fruit juice of Citrus limon as a biodegradable and reusable catalyst for facile, eco-friendly and green synthesis of 3,4-disubstituted isoxazol-5(4H)-ones and dihydropyrano[2,3-c]-pyrazole derivatives

Thiourea dioxide: An efficient and reusable organocatalyst for the rapid one-pot synthesis of pyrano[4, 3- b ]pyran derivatives in water

A general and efficient one-pot synthesis of spiro[2-amino-4H-pyrans] via tandem multi-component reactions catalyzed by Dabco-based ionic liquids

A new series of chromeno-annulated cis-fused pyrano[3,4-c]pyran derivatives have been synthesized by intramolecular [4 + 2] domino Knoevenagel–hetero-Diels–Alder reactions of 1-oxa-1,3-butadienes derived in situ from 1,3-dicarbonyls/active methylenes and 7-O-prenyl derivatives of 8-formyl-2,3-disubstituted chromenones in the presence of 20 mol% ethylenediamine diacetate (EDDA) in acetonitrile under reflux conditions in good to excellent yields. The structures were established based on spectroscopic data, and were further confirmed by X-ray diffraction analysis. These compounds were evaluated for their anti-proliferative activity using an in vitro MTT cytotoxicity assay. The results clearly demonstrated that compounds 4a, 4b, 4c, 4j, 4k, 4l, 4m and 4n exhibited significant anti-proliferative activity against human A549 lung cancer and non-cancer MRC-5 cell lines along with potent inhibitory activity against human neuroblastoma SK-N-SH cancer cell lines. Among these, compounds 4a, 4b and 4j displayed the most potent anti-proliferative activity against human lung cancer A549 cell lines, while 4a and 4b displayed against neuroblastoma SK-N-SH cancer cell lines when compared to the standard doxorubicin.

Synthesis of new chromeno-annulated cis-fused pyrano[3,4-c]pyran derivatives via domino Knoevenagel–hetero-Diels–Alder reactions and their biological evaluation towards antiproliferative activity

G. RoopaJones

Papers

Synthesis of new chromeno-annulated cis-fused pyrano[3,4-c]pyran derivatives via domino Knoevenagel–hetero-Diels–Alder reactions and their biological evaluation towards antiproliferative activity