Expanding the Toolbox of Heterogeneous Asymmetric Organocatalysts: Bifunctional Cyclopropenimine Superbases for Enantioselective Catalysis in Batch and Continuous Flow
| Autor: | Olga Bortolini, Costanza Leonardi, Paolo Dambruoso, Arianna Brandolese, Eleonora Polo, Graziano Di Carmine, Alessandro Massi, Daniele Ragno, Lorenzo Preti |
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| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Chemistry
flow chemistry Enantioselective synthesis Ambientale asymmetric catalysis packed-bed reactor General Chemistry Flow chemistry Heterogeneous catalysis Brønsted base Combinatorial chemistry asymmetric catalysis Brønsted base C-C coupling flow chemistry heterogeneous catalysis immobilization Michael addition organocatalysis packed-bed reactor Catalysis chemistry.chemical_compound Bronsted base heterogeneous catalysis Organocatalysis Michael addition immobilization Michael reaction organocatalysis C-C coupling Bifunctional Brønsted–Lowry acid–base theory |
| Zdroj: | Advanced synthesis & catalysis 363 (2021): 5473–5485. doi:10.1002/adsc.202100757 info:cnr-pdr/source/autori:Leonardi, Costanza; Brandolese, Arianna; Preti, Lorenzo; Bortolini, Olga; Polo, Eleonora; Dambruoso, Paolo; Ragno, Daniele; Di Carmine, Graziano; Massi, Alessandro/titolo:Expanding the Toolbox of Heterogeneous Asymmetric Organocatalysts: Bifunctional Cyclopropenimine Superbases for Enantioselective Catalysis in Batch and Continuous Flow/doi:10.1002%2Fadsc.202100757/rivista:Advanced synthesis & catalysis (Print)/anno:2021/pagina_da:5473/pagina_a:5485/intervallo_pagine:5473–5485/volume:363 |
| DOI: | 10.1002/adsc.202100757 |
| Popis: | A strategy for the immobilization of chiral 2,3-bisaminocyclopropenium salt (pre-catalyst) onto polystyrene and silica supports is presented together with a suitable procedure for the conversion into the corresponding cyclopropenimine superbase catalysts. The activity and recyclability of polystyrene- and silica-supported cyclopropenimines were initially tested under batch conditions in a model Michael addition detecting comparable efficiencies but a superior stability of the latter heterogeneous catalyst (5 cycles, accumulated TON of 27.1). The preferred silica-supported cyclopropenimine behaved very similarly to the soluble counterpart in the reaction of glycine imine with different Michael acceptors (48-92% yield; 60-98% ee) and it could be utilized as packing material for the fabrication of fixed-bed mesoreactors (pressure-resistant stainless-steel columns). Continuous-flow experiments were performed with satisfactory long-term stability (24 h on stream) with unaltered conversion efficiency and enantioselectivity. |
| Databáze: | OpenAIRE |
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