Esterification of glycerol and solketal by oxidative NHC-catalysis under heterogeneous batch and flow conditions

Daniele Ragno; Arianna Brandolese; Daniele Urbani; Graziano Di Carmine; Carmela De Risi; Olga Bortolini; Pier Paolo Giovannini; Alessandro Massi

doi:10.1039/c8re00143j

Esterification of glycerol and solketal by oxidative NHC-catalysis under heterogeneous batch and flow conditions

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

^*Corresponding author for this work

Chemistry

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

17 Citations (Scopus)

Abstract

The design and synthesis of a set of supported azolium salt pre-catalysts is presented along with their utilization in the production of monoesters of glycerol and solketal by oxidative N-heterocyclic carbene (NHC)-catalysis through batch and continuous-flow approaches. After a propaedeutic study with soluble NHCs, the heterogeneous analogues (silica and polystyrene supports) were tested in a model monoesterification of glycerol using either the Kharasch oxidant or air (in the presence of electron transfer mediators) as the terminal oxidants. The best performing polystyrene-supported triazolium salt pre-catalyst afforded monoacylglycerols (MAGs) in high yields (up to 95%) and almost complete selectivity (monoester/diester >95:5) using air and the green solvent Me-THF. The synthesis of fully bio-based MAGs from furfural, 5-hydroxymethylfurfural (HMF), citronellal, and vanillin is also reported. Continuous-flow experiments have been finally performed by fabricating the corresponding packed-bed microreactor, which could be operated for ca. 120 hours with maintenance of conversion efficiency and selectivity.

Original language	English
Pages (from-to)	816-825
Number of pages	10
Journal	Reaction Chemistry and Engineering
Volume	3
Issue number	5
DOIs	https://doi.org/10.1039/c8re00143j
Publication status	Published - Oct 2018

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:
© 2018 The Royal Society of Chemistry.

ASJC Scopus subject areas

Catalysis
Chemistry (miscellaneous)
Chemical Engineering (miscellaneous)
Process Chemistry and Technology
Fluid Flow and Transfer Processes

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title = "Esterification of glycerol and solketal by oxidative NHC-catalysis under heterogeneous batch and flow conditions",

abstract = "The design and synthesis of a set of supported azolium salt pre-catalysts is presented along with their utilization in the production of monoesters of glycerol and solketal by oxidative N-heterocyclic carbene (NHC)-catalysis through batch and continuous-flow approaches. After a propaedeutic study with soluble NHCs, the heterogeneous analogues (silica and polystyrene supports) were tested in a model monoesterification of glycerol using either the Kharasch oxidant or air (in the presence of electron transfer mediators) as the terminal oxidants. The best performing polystyrene-supported triazolium salt pre-catalyst afforded monoacylglycerols (MAGs) in high yields (up to 95%) and almost complete selectivity (monoester/diester >95:5) using air and the green solvent Me-THF. The synthesis of fully bio-based MAGs from furfural, 5-hydroxymethylfurfural (HMF), citronellal, and vanillin is also reported. Continuous-flow experiments have been finally performed by fabricating the corresponding packed-bed microreactor, which could be operated for ca. 120 hours with maintenance of conversion efficiency and selectivity.",

author = "Daniele Ragno and Arianna Brandolese and Daniele Urbani and {Di Carmine}, Graziano and {De Risi}, Carmela and Olga Bortolini and Giovannini, {Pier Paolo} and Alessandro Massi",

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} 2018 The Royal Society of Chemistry.",

year = "2018",

month = oct,

doi = "10.1039/c8re00143j",

language = "English",

volume = "3",

pages = "816--825",

journal = "Reaction Chemistry and Engineering",

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publisher = "Royal Society of Chemistry",

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AU - Ragno, Daniele

AU - Brandolese, Arianna

AU - Urbani, Daniele

AU - Di Carmine, Graziano

AU - De Risi, Carmela

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: © 2018 The Royal Society of Chemistry.

PY - 2018/10

Y1 - 2018/10

N2 - The design and synthesis of a set of supported azolium salt pre-catalysts is presented along with their utilization in the production of monoesters of glycerol and solketal by oxidative N-heterocyclic carbene (NHC)-catalysis through batch and continuous-flow approaches. After a propaedeutic study with soluble NHCs, the heterogeneous analogues (silica and polystyrene supports) were tested in a model monoesterification of glycerol using either the Kharasch oxidant or air (in the presence of electron transfer mediators) as the terminal oxidants. The best performing polystyrene-supported triazolium salt pre-catalyst afforded monoacylglycerols (MAGs) in high yields (up to 95%) and almost complete selectivity (monoester/diester >95:5) using air and the green solvent Me-THF. The synthesis of fully bio-based MAGs from furfural, 5-hydroxymethylfurfural (HMF), citronellal, and vanillin is also reported. Continuous-flow experiments have been finally performed by fabricating the corresponding packed-bed microreactor, which could be operated for ca. 120 hours with maintenance of conversion efficiency and selectivity.

AB - The design and synthesis of a set of supported azolium salt pre-catalysts is presented along with their utilization in the production of monoesters of glycerol and solketal by oxidative N-heterocyclic carbene (NHC)-catalysis through batch and continuous-flow approaches. After a propaedeutic study with soluble NHCs, the heterogeneous analogues (silica and polystyrene supports) were tested in a model monoesterification of glycerol using either the Kharasch oxidant or air (in the presence of electron transfer mediators) as the terminal oxidants. The best performing polystyrene-supported triazolium salt pre-catalyst afforded monoacylglycerols (MAGs) in high yields (up to 95%) and almost complete selectivity (monoester/diester >95:5) using air and the green solvent Me-THF. The synthesis of fully bio-based MAGs from furfural, 5-hydroxymethylfurfural (HMF), citronellal, and vanillin is also reported. Continuous-flow experiments have been finally performed by fabricating the corresponding packed-bed microreactor, which could be operated for ca. 120 hours with maintenance of conversion efficiency and selectivity.

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Esterification of glycerol and solketal by oxidative NHC-catalysis under heterogeneous batch and flow conditions

Abstract

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