One-Pot Synthesis of Biologically Important Spiro-2-amino-4H-pyrans, Spiroacenaphthylenes, and Spirooxindoles Using DBU as a Green and Recyclable Catalyst in Aqueous Medium

Green Synthetic Approaches for Biologically Relevant 2-amino-4H-pyrans and 2-amino-4H-pyran-Annulated Heterocycles in Aqueous Media∗

“…in aqueous media in the presence of different homogeneous or heterogeneous catalysts in good to excellent yields; catalyst-free synthesis of such scaffolds was also reported (Scheme 18) [88,95,[114][115][116][117][118][119][120].…”

“…The same groups of investigators also explored their protocol in case of barbituric acid or 6-thioxodihydropyrimidine-2,4(1H,3H)-dione (17) A variety of substituted spiroacenaphthylene derivatives 39 were also synthesized in water from the one-pot multicomponent reaction of acenaphthenequinone (24), cyclic 1,3-diketone, and malononitrile/ethyl cyanoacetate 3 in the presence or absence of catalysts under reflux conditions (Scheme 21) [118,120,122,123].…”

“…A library of spiroacenaphthylenes 40-42 were synthesized using the same techniques just by varying 1,3-dicarbonyls (11,13, and 17) in water medium (Scheme 22) [118,122,123]. …”

Caspian Isinglass, a versatile and sustainable biocatalyst for domino synthesis of spirooxindoles and spiroacenaphthylenes in water

“…A number of methods have been developed for the synthesis of such compounds and the chemistry was comprehensively reviewed by several groups [12,13,19,[31][32][33][34][35][36][37][38].…”

Synthesis of spirooxindole pyrimidines catalyzed by silica-bonded N-propyltriethylenetetramine as a recyclable solid base catalyst in aqueous medium

“…Among them, the one-pot condensation reaction of isatin and activated methylene reagent could readily afford various spirooxindole pyramidine structures and has attracted wide attention, and this type of reaction has been achieved by a number of different catalysts and conditions, such as InCl 3 [43], electrochemical methods [44], triethylbenzylammonium chloride (TEBA) [45], Et 3 N [46], tetrabutylammonium fluoride (TBAF) [47], NH 4 Cl [48], lipase [4], p-TSA [49], ZnS nanoparticles [50], NaCl under sonication [51], butylmethylimidazolium tetrafluoroborate ([BMIm]BF 4 ) [52], amino-functionalized SBA-15 [53], CaCl 2 under ultrasonic irradiation [54], piperidine under ultrasonic irradiation [55], nanocrystalline MgO [56], gluconic acid [57], MnFe 2 O 4 nanoparticles [58], 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU) [59], ethylenediammonium diformate (EDDF) [60], and sulfated choline based heteropolyanion [61] which some of them suffer from technical intricacy and generation of mixtures of pyrans and unsaturated nitriles.…”