Pyrrolidine-based catalytic microporous polymers in sustainable C=N and C=C bond formation via iminium and enamine activation

Producción CientíficaA new set of catalytic materials having a pyrrolidine moiety confined in microporous organic polymer networks (POPs) has been attained. These catalytic polymers have been prepared by a straightforward synthesis starting from microporous polymer networks made from isatin (or a mixture of isatin and trifluoroacetophenone) and 1,3,5-triphenylbenzene. The polymers efficiently catalyzed the formation of nitrones under very mild and sustainable conditions using green solvents through an iminium ion activation mechanism. The reactions are scalable, and polymers are easily recycled. Special attention has been paid to understanding all the factors that could affect the efficiency of the confined catalysts. The electronic and conformational characteristics of the pyrrolidine moiety attached to the porous polymers, as well as other features that could affect the transport through the network, such as molecular volume and shape of reactants and products, and even hydrophilic or hydrophobic properties, have been systematically evaluated. In addition, the heterogeneous polymers are also useful in Cdouble bondC bond formation through both iminium ion and enamine activation.Gobierno de España (Agencia Estatal de Investigación) - (Projects CTQ2016-78779-R, PID2019-109403RB-C22, RTI2018-096328-B-I00, CTQ2017-89217-P and PID2020-118547GBI00)Junta de Castilla y León, Unión Europea y Fondo Europeo de Desarrollo Regional (FEDER) - (Project VA224P20)

Pyrrolidine-based catalytic microporous polymers in sustainable C[dbnd]N and C[dbnd]C bond formation via iminium and enamine activation

A new set of catalytic materials having a pyrrolidine moiety confined in microporous organic polymer networks (POPs) has been attained. These catalytic polymers have been prepared by a straightforward synthesis starting from microporous polymer networks made from isatin (or a mixture of isatin and trifluoroacetophenone) and 1,3,5-triphenylbenzene. The polymers efficiently catalyzed the formation of nitrones under very mild and sustainable conditions using green solvents through an iminium ion activation mechanism. The reactions are scalable, and polymers are easily recycled. Special attention has been paid to understanding all the factors that could affect the efficiency of the confined catalysts. The electronic and conformational characteristics of the pyrrolidine moiety attached to the porous polymers, as well as other features that could affect the transport through the network, such as molecular volume and shape of reactants and products, and even hydrophilic or hydrophobic properties, have been systematically evaluated. In addition, the heterogeneous polymers are also useful in C[dbnd]C bond formation through both iminium ion and enamine activation.We acknowledge the Spanish Government (Agencia Estatal de Investigación projects; CTQ2016-78779-R, PID2019-109403RB-C22, RTI2018-096328-B-I00, CTQ2017-89217-P and PID2020-118547GB- I00), and the Regional Government of Castilla y León (project CyL and EU-FEDER program VA224P20), for financial support. E. L. Vargas thanks University of Costa Rica for a PhD scholarship. We must thank Rebecca Chevillard and Valentina Petrelli for some preliminary experiments