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

ABSTRACT: 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.

SUBMITTER: Andres JM

PROVIDER: S-EPMC6644291 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

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

Andrés José M JM Maestro Alicia A Valle María M Valencia Isabel I Pedrosa Rafael R

ACS omega 20181205 12

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-<b>9</ ...[more]

PMID: 31458291

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