Basic-carbon nanocatalysts in the efficient synthesis of chromene derivatives. Valorization of both PET residues and mineral sources

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2020-02, Vol.382, p.122795, Article 122795
• Main Authors: González-Rodal, D., Przepiórski, J., López Peinado, A.J., Pérez-Mayoral, E.
• Format: Article
• Language: English
• Subjects: Carbon-based catalysts; Cascade reactions; Chromenes; Heterogeneous catalysis; Multicomponent synthesis
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2019.122795

[Display omitted] •PET and limestone can be easily converted to carbon-based catalysts by heating.•Polluting plastic residues are used for production of CaO supported on porous carbons.•PET/CAL efficiently catalyzes synthesis 2-amino-4H-chromenes under mild conditions.•The reaction is strongly favored in the presence of the CaO-containing catalysts. Novel series of calcium oxide (calcium hydroxide)/carbon composites applied to the green and efficient synthesis of 2-amino-4H-chromenes, from salicylaldehydes and ethyl cyanoacetate, under mild and free-solvent conditions, is herein reported for the first time. These basic hybrid materials are easily prepared by direct thermal pyrolysis of limestone and PET. Different Ca-phases, CaO or Ca(OH)2, were independently detected, since CaO/carbon composites initially formed can be easily hydrated, under atmospheric conditions, but also dehydrated by re-calcination. CaO-containing samples present enhanced catalytic performance, the observed reactivity being attributed to the catalyst basicity. The reaction under study catalyzed by CaO probably occurs by cascade reactions through aldolization – heterocyclization – dehydration – Michael addition sequence, strongly favored by the presence of the truly active phase, CaO, as experimental and theoretical demonstrated. The methodology herein reported can be framed in circular economy domain opening the possibility of synthetizing valuable compounds from carbon-based catalysts prepared by using plastic residues as PET source.