Diastereo- and Enantioselective Syntheses of Trisubstituted Benzopyrans by Cascade Reactions Catalyzed by Monomeric and Polymeric Recoverable Bifunctional Thioureas and Squaramides

Authors :: Isabel Valencia
Alicia Maestro
María Valle
José M. Andrés
Rafael Pedrosa
Source :: ACS Omega, UVaDOC. Repositorio Documental de la Universidad de Valladolid, instname, ACS Omega, Vol 3, Iss 12, Pp 16591-16600 (2018)
Publication Year :: 2018
Publisher :: American Chemical Society (ACS), 2018.
Abstract: Producción Científica<br />4-Vinylphenyl-substituted squaramides have been tested as organocatalysts for the diastereo- and enantioselective synthesis of trisubstituted benzopyrans via an oxa-Michael intramolecular nitro-Michael cascade reaction. Both the enantio- and diastereoselection were good to moderate, depending on the nature of the chiral scaffold in the catalyst. The diastereoselection is better for the most active catalyst because the final products epimerize at C-3 along the time. Supported squaramide sq-9 prepared by copolymerization of sq-4 with styrene and divinylbenzene is also effective in promoting the cascade reaction, and it is recoverable and reusable for five cycles maintaining the activity.<br />Ministerio de Economía, Industria y Competitividad (Project FEDER-CTQ2014-59870-P)<br />Junta de Castilla y León (Projects FEDER-VA115P17 and VA149G18)

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