Immobilization of Privileged Triazolium Carbene Catalyst for Batch and Flow Stereoselective Umpolung Processes

Daniele Ragno; Graziano Di Carmine; Arianna Brandolese; Olga Bortolini; Pier Paolo Giovannini; Alessandro Massi

doi:10.1021/acscatal.7b02164

Immobilization of Privileged Triazolium Carbene Catalyst for Batch and Flow Stereoselective Umpolung Processes

Daniele Ragno, Graziano Di Carmine, Arianna Brandolese, Olga Bortolini, Pier Paolo Giovannini, Alessandro Massi^*

^*Corresponding author for this work

Chemistry

Research output: Contribution to journal › Article › peer-review

42 Citations (Scopus)

Abstract

A strategy for the immobilization of the valuable triazolium carbene Rovis catalyst onto polystyrene and silica supports is presented. Initially, the catalyst activity and recyclability were tested under batch conditions in the model stereoselective intramolecular Stetter reaction leading to optically active chromanones. Good results in terms of yield (95%) and enantioselectivity (ee 81-95%) were detected for the polystyrene-supported catalyst (10 mol %), while poorer results were collected for the silica-supported analogue. Also, continuous-flow experiments were performed by fabricating the corresponding polystyrene monolithic microreactors (pressure-resistant stainless-steel columns) to prove the benefits of the heterogeneous catalysis and the flow regime observing a high stability of the catalytic bed (48 h) with unaltered conversion efficiency and stereoselectivity.

Original language	English
Pages (from-to)	6365-6375
Number of pages	11
Journal	ACS Catalysis
Volume	7
Issue number	9
DOIs	https://doi.org/10.1021/acscatal.7b02164
Publication status	Published - 1 Sept 2017

Bibliographical note

Funding Information:
We gratefully acknowledge the University of Ferrara (fondi FAR) for financial support. Thanks are also given to Paolo Formaglio for NMR experiments, to Tatiana Bernardi for HRMS analyses, and to Ercolina Bianchini for elemental analyses.

Publisher Copyright:
© 2017 American Chemical Society.

Keywords

chiral N-heterocyclic carbenes
enantioselective catalysis
flow chemistry
organocatalysis
polystyrene-supported catalysts

ASJC Scopus subject areas

Catalysis
General Chemistry

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abstract = "A strategy for the immobilization of the valuable triazolium carbene Rovis catalyst onto polystyrene and silica supports is presented. Initially, the catalyst activity and recyclability were tested under batch conditions in the model stereoselective intramolecular Stetter reaction leading to optically active chromanones. Good results in terms of yield (95%) and enantioselectivity (ee 81-95%) were detected for the polystyrene-supported catalyst (10 mol %), while poorer results were collected for the silica-supported analogue. Also, continuous-flow experiments were performed by fabricating the corresponding polystyrene monolithic microreactors (pressure-resistant stainless-steel columns) to prove the benefits of the heterogeneous catalysis and the flow regime observing a high stability of the catalytic bed (48 h) with unaltered conversion efficiency and stereoselectivity.",

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note = "Funding Information: We gratefully acknowledge the University of Ferrara (fondi FAR) for financial support. Thanks are also given to Paolo Formaglio for NMR experiments, to Tatiana Bernardi for HRMS analyses, and to Ercolina Bianchini for elemental analyses. Publisher Copyright: {\textcopyright} 2017 American Chemical Society.",

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AU - Di Carmine, Graziano

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AU - Bortolini, Olga

AU - Giovannini, Pier Paolo

AU - Massi, Alessandro

N1 - Funding Information: We gratefully acknowledge the University of Ferrara (fondi FAR) for financial support. Thanks are also given to Paolo Formaglio for NMR experiments, to Tatiana Bernardi for HRMS analyses, and to Ercolina Bianchini for elemental analyses. Publisher Copyright: © 2017 American Chemical Society.

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N2 - A strategy for the immobilization of the valuable triazolium carbene Rovis catalyst onto polystyrene and silica supports is presented. Initially, the catalyst activity and recyclability were tested under batch conditions in the model stereoselective intramolecular Stetter reaction leading to optically active chromanones. Good results in terms of yield (95%) and enantioselectivity (ee 81-95%) were detected for the polystyrene-supported catalyst (10 mol %), while poorer results were collected for the silica-supported analogue. Also, continuous-flow experiments were performed by fabricating the corresponding polystyrene monolithic microreactors (pressure-resistant stainless-steel columns) to prove the benefits of the heterogeneous catalysis and the flow regime observing a high stability of the catalytic bed (48 h) with unaltered conversion efficiency and stereoselectivity.

AB - A strategy for the immobilization of the valuable triazolium carbene Rovis catalyst onto polystyrene and silica supports is presented. Initially, the catalyst activity and recyclability were tested under batch conditions in the model stereoselective intramolecular Stetter reaction leading to optically active chromanones. Good results in terms of yield (95%) and enantioselectivity (ee 81-95%) were detected for the polystyrene-supported catalyst (10 mol %), while poorer results were collected for the silica-supported analogue. Also, continuous-flow experiments were performed by fabricating the corresponding polystyrene monolithic microreactors (pressure-resistant stainless-steel columns) to prove the benefits of the heterogeneous catalysis and the flow regime observing a high stability of the catalytic bed (48 h) with unaltered conversion efficiency and stereoselectivity.

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Immobilization of Privileged Triazolium Carbene Catalyst for Batch and Flow Stereoselective Umpolung Processes

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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