A heterogeneous, silica-based catalyst containing 9-amino-9-deoxy-epi-quinine (or quinidine) and a derivative of benzoic acid was synthesized through radical thiol-ene click reaction. The acid component allows the in situ activation of cinchona amino group, acting as a bifunctional catalyst. The heterogenized catalysts efficiently promoted the reaction of ketones with trans-β-nitrostyrene, with diastereo- and enantioselectivity comparable to those of the homogeneous counterparts (dr up to 90:10 and 90 % ee). In addition, the catalyst retained a constant activity for at least four cycles. Finally, the supported catalyst (9-amino-9-deoxy-epi-quinine/achiral acid) was employed under continuous-flow conditions. Two enantioselective Michael reactions were in sequence performed with the same homemade packed-bed reactor. The addition of cyclohexanone to trans-β-nitrostyrene provided the evaluation of optimal residence time with high level of stereoselection (2 µL/min flow rate, 83 % ee). Furthermore, the flow reactor well performed in the preparation of warfarin (isolated yield 95 %, 78 % ee. in 16 h at room temperature). The dual (chiral amine/achiral acid) solid supported system, making an even easier work-out, represents a valuable tool for green chemistry and is attractive for large scale applications. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

A silica-supported catalyst containing 9-amino-9-deoxy-9-epi-quinine and a benzoic acid derivative for stereoselective batch and flow heterogeneous reactions / Ciogli, Alessia; Capitani, Donatella; Di Iorio, Nicola; Crotti, Simone; Bencivenni, Giorgio; Donzello, Maria Pia; Villani, Claudio. - In: EUROPEAN JOURNAL OF ORGANIC CHEMISTRY. - ISSN 1434-193X. - 2019:10(2019), pp. 2020-2028. [10.1002/ejoc.201900148]

A silica-supported catalyst containing 9-amino-9-deoxy-9-epi-quinine and a benzoic acid derivative for stereoselective batch and flow heterogeneous reactions

Ciogli, Alessia
;
Donzello, Maria Pia;Villani, Claudio
2019

Abstract

A heterogeneous, silica-based catalyst containing 9-amino-9-deoxy-epi-quinine (or quinidine) and a derivative of benzoic acid was synthesized through radical thiol-ene click reaction. The acid component allows the in situ activation of cinchona amino group, acting as a bifunctional catalyst. The heterogenized catalysts efficiently promoted the reaction of ketones with trans-β-nitrostyrene, with diastereo- and enantioselectivity comparable to those of the homogeneous counterparts (dr up to 90:10 and 90 % ee). In addition, the catalyst retained a constant activity for at least four cycles. Finally, the supported catalyst (9-amino-9-deoxy-epi-quinine/achiral acid) was employed under continuous-flow conditions. Two enantioselective Michael reactions were in sequence performed with the same homemade packed-bed reactor. The addition of cyclohexanone to trans-β-nitrostyrene provided the evaluation of optimal residence time with high level of stereoselection (2 µL/min flow rate, 83 % ee). Furthermore, the flow reactor well performed in the preparation of warfarin (isolated yield 95 %, 78 % ee. in 16 h at room temperature). The dual (chiral amine/achiral acid) solid supported system, making an even easier work-out, represents a valuable tool for green chemistry and is attractive for large scale applications. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
continuous flow; aminocatalysis; supported catalysts; asymmetric catalysis; heterogeneous reactions
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A silica-supported catalyst containing 9-amino-9-deoxy-9-epi-quinine and a benzoic acid derivative for stereoselective batch and flow heterogeneous reactions / Ciogli, Alessia; Capitani, Donatella; Di Iorio, Nicola; Crotti, Simone; Bencivenni, Giorgio; Donzello, Maria Pia; Villani, Claudio. - In: EUROPEAN JOURNAL OF ORGANIC CHEMISTRY. - ISSN 1434-193X. - 2019:10(2019), pp. 2020-2028. [10.1002/ejoc.201900148]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1271770
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