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Catalytic Enantioselective Povarov Reactions of Ferrocenecarbaldehyde‐Derived Imines – Brønsted Acid Catalysis at Parts‐Per‐Million Level Loading
Author(s) -
Stevanović Dragana,
Bertuzzi Giulio,
Mazzanti Andrea,
Fochi Mariafrancesca,
Bernardi Luca
Publication year - 2018
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201701484
Subject(s) - enantiopure drug , enantioselective synthesis , chemistry , catalysis , brønsted–lowry acid–base theory , phosphoric acid , ferrocene , organic chemistry , aryl , combinatorial chemistry , electrochemistry , alkyl , electrode
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 0.1 mol% of a standard Brønsted 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.