A metal-free porphyrin heterogenised onto SBA-15 silica: A performant material for the CO2 cycloaddition to epoxides and aziridines

The covalently heterogenisation of a free-base porphyrin on SBA-15 silica yielded TPPH2@SBA-15 (TPPH2 = tetraphenyl porphyrin), which was very efficient to promote the CO2 cycloaddition to three -membered rings. The TPPH2@SBA-15/TBAX-based catalytic procedure was very general, as revealed by excellent activities registered in the reaction of CO2 with epoxides, N-alkyl and N-aryl aziridines, forming cyclic carbonates, N-alkyl and N-aryl oxazolidinones, respectively. It is worth noting that this is the first example of the heterogeneously catalysed synthesis of N-aryl oxazolidinones from corresponding N-aryl aziridines. The scale-up of the methodology highlighted that catalytic performances of all the three investigated reactions were maintained also working at a gram-scale to pave the way for future developments of the procedure. In addition, the recycle of TPPH2@SBA-15 for several consecutive reactions was efficient and observed catalytic activities were very similar to those registered in the presence of a fresh material. All the acquired data indicated an excellent sustainability of the catalytic protocol to envisage upcoming practical applications. (C) 2022 Elsevier Inc. All rights reserved.

Automated summary

This study achieved the covalent immobilization of a free-base porphyrin on SBA-15 silica and utilized it for the catalytic cycloaddition of CO2 to three-membered rings. The catalytic system based on TPPH2@SBA-15/TBAX exhibited excellent activities in reactions with epoxides, N-alkyl, and N-aryl aziridines, resulting in cyclic carbonates and N-alkyl/aryl oxazolidinones, respectively. Notably, this is the first example of the heterogeneously catalyzed synthesis of N-aryl oxazolidinones from corresponding N-aryl aziridines. The methodology showed good scalability and recyclability, indicating its potential for practical applications.