Despite the broad interest in ferrocene containing compounds, ferrocenyl substrates have been employed in catalytic asymmetric settings only sporadically. Herein, catalytic asymmetric Povarov reactions with ferrocenecarbaldehyde-derived N-aryl imines are presented. This study demonstrates that the stereoelectronic properties of ferrocenyl imines do not preclude their engagement in enantioselective phosphoric acid catalysis: cycloadducts derived from benzyl N-vinylcarbamate were obtained in good yields and nearly enantiopure form using 0.1mol% of a standard Bronsted acid catalyst. Furthermore, it is shown that specific optimisation with some substrates allowed to lower the catalyst loading up to 10-20 parts-per-million, an unprecedented value for phosphoric acid catalysts. Such low loading protocol could be applied to a preparative scale reaction, and to imines derived from arylaldehydes.

Catalytic Enantioselective Povarov Reactions of Ferrocenecarbaldehyde-Derived Imines - Bronsted Acid Catalysis at Parts-Per-Million Level Loading

Bertuzzi, Giulio;Mazzanti, Andrea;Fochi, Mariafrancesca
;
Bernardi, Luca
2018

Abstract

Despite the broad interest in ferrocene containing compounds, ferrocenyl substrates have been employed in catalytic asymmetric settings only sporadically. Herein, catalytic asymmetric Povarov reactions with ferrocenecarbaldehyde-derived N-aryl imines are presented. This study demonstrates that the stereoelectronic properties of ferrocenyl imines do not preclude their engagement in enantioselective phosphoric acid catalysis: cycloadducts derived from benzyl N-vinylcarbamate were obtained in good yields and nearly enantiopure form using 0.1mol% of a standard Bronsted acid catalyst. Furthermore, it is shown that specific optimisation with some substrates allowed to lower the catalyst loading up to 10-20 parts-per-million, an unprecedented value for phosphoric acid catalysts. Such low loading protocol could be applied to a preparative scale reaction, and to imines derived from arylaldehydes.
Stevanovic, Dragana; Bertuzzi, Giulio; Mazzanti, Andrea; Fochi, Mariafrancesca; Bernardi, Luca
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11585/657067
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