Domino dehydration/intermolecular (enantioselective) ketone-ene reactions catalysed by a simple solid in batch and in flow

The intermolecular carbonyl-ene reaction of ketones is still considered a challenge in organic chemistry, particularly with reusable solid catalysts, and implemented in a domino reaction. Herein, we show that the extremely cheap and non-toxic solid salt MgCl 2 catalyzes the reaction of trifluorometh...

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Bibliographic Details
Published in:RSC advances 2024-10, Vol.14 (45), p.32944-32957
Main Authors: Espinosa, Miguel, Leyva-Pérez, Antonio
Format: Article
Language:English
Subjects:
Alcohols
Alkenes
Carbonyls
Cascade chemical reactions
Catalysts
Catalytic activity
Citronellal
Dehydration
Enantiomers
Extreme values
Ketones
Magnesium chloride
Organic chemistry
Pyruvates
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Summary:The intermolecular carbonyl-ene reaction of ketones is still considered a challenge in organic chemistry, particularly with reusable solid catalysts, and implemented in a domino reaction. Herein, we show that the extremely cheap and non-toxic solid salt MgCl 2 catalyzes the reaction of trifluoromethyl pyruvates not only during the conventional carbonyl-ene reaction with various aromatic and alkyl alkenes (in very high yields, up to >99%) but also in a domino reaction with the corresponding alcohols (precursors to the alkenes) in similar good yields. The solid can be reused in both cases without any erosion of the catalytic activity and can be employed in an in-flow process to maximize the reaction throughput. Besides, the reaction can be performed under solventless reaction conditions. Addition of a catalytic amount of chiral binaphthyl hydrogen phosphate allows carrying out the reaction with a reasonable enantiomeric excess (up to >70%) and in flow, in a rare example of enantioselective solid-catalyzed domino carbonyl-ene reaction using a cheap, simple, readily available and physically mixed catalytic solid. The MgCl 2 -catalytic system is also active in the industrially relevant citronellal-to-isopulegol carbonyl-ene reaction. These results pave the way to design sustainable domino carbonyl-ene reactions with extremely cheap solid catalysts. Extremely cheap solids catalyse the one-pot dehydration/intermolecular ketone-ene reaction in batch and in flow, and also enantioselectively.
ISSN:2046-2069
2046-2069
DOI:10.1039/d4ra06449f