title: A facile, efficient, and sustainable chitosan/CaHAp catalyst and one-pot synthesis of novel 2,6-diamino-pyran-3,5-dicarbonitriles.
abstract: A simple and versatile one-pot three-component synthetic protocol is devised for heterocycles, viz. 2,6-diamino-4-substituted-4H-pyran-3,5-dicarbonitrile derivatives, in short reaction times ([Formula: see text]30 min) at room temperature using ethanol as a solvent. This method involves the three-component reaction of malononitrile, substituted aldehydes, and cyanoacetamide catalyzed by chitosan-doped calcium hydroxyapatites (CS/CaHAps) giving good to excellent yields (86-96%). Twelve new pyran derivatives (4a-l) were synthesized and their structures were established and confirmed by different spectroscopic methods ([Formula: see text]H NMR, [Formula: see text]C NMR, [Formula: see text]N NMR, and HRMS). The heterogeneous catalyst, CS/CaHAp, was characterized by various instrumental techniques including XRD, TEM, SEM, and FT-IR and TGA spectroscopies. The catalyst was easily separable and reusable for up to six runs without any apparent loss of activity. The reported protocol has many benefits, such as ease of preparation, use of a green solvent, reduced reaction times, excellent product yields, and operational simplicity.
authors.affiliation: School of Chemistry & Physics, University of KwaZulu-Natal, Westville Campus, Chiltern Hills, Durban, 4000, South Africa.
authors.forename: Suresh
authors.initials: S
authors.lastname: Maddila
authors.affiliation: School of Chemistry & Physics, University of KwaZulu-Natal, Westville Campus, Chiltern Hills, Durban, 4000, South Africa.
authors.forename: Kranthi Kumar
authors.initials: KK
authors.lastname: Gangu
authors.affiliation: School of Chemistry & Physics, University of KwaZulu-Natal, Westville Campus, Chiltern Hills, Durban, 4000, South Africa.
authors.forename: Surya Narayana
authors.initials: SN
authors.lastname: Maddila
authors.affiliation: School of Chemistry & Physics, University of KwaZulu-Natal, Westville Campus, Chiltern Hills, Durban, 4000, South Africa. jonnalagaddas@ukzn.ac.za.
authors.forename: Sreekantha B
authors.identifier: http://orcid.org/0000-0001-6501-8875
authors.initials: SB
authors.lastname: Jonnalagadda
mesh_terms: D002384:Catalysis; D060326:Chemistry Techniques, Synthetic; D048271:Chitosan / Q000737:chemistry*; D017886:Durapatite / Q000737:chemistry*; D055772:Green Chemistry Technology; D009570:Nitriles / Q000138:chemical synthesis* / Q000737:chemistry*; D011714:Pyrans / Q000737:chemistry*
chemical_list: D009570:Nitriles; D011714:Pyrans; D048271:Chitosan; D017886:Durapatite
keywords: Chitosan; Green synthesis; Heterogeneous catalyst; Hydroxyapatite; MCRs; Multicomponent reactions; Pyrans; Recyclability