Chemoselective reduction of α,β-unsaturated aldehydes and ketones over mesoporous B(O i Pr)3–MCM-41 catalyst via MPV reduction process: preparation, characterization and catalytic application

AbstractCatalytic Meerwein-Ponndorf-Verley (MPV) reduction of various aliphatic, aromatic, and unsaturated aldehydes and ketones to corresponding alcohols (analyzed by GC-MS) in the presence of boron triethoxide (B(OEt)3) were studied. Kinetics of this reduction reaction was also studied and the respective rate constants were determined. It was found that B(OEt)3 catalyzes the reduction of aliphatic aldehydes and ketones to alcohols at room temperature while aromatic aldehydes and ketones were not reduced under the same conditions. In addition, MPV reduction using B(OEt)3 was found to be chemoselective as unsaturated aldehydes and ketones afforded the corresponding alcohols without affecting unsaturated groups. The mechanism proposed involves a six-membered transition state in which both the alcohol and the carbonyl are coordinated to the same boron centre of a boron alkoxide catalyst.

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Comparison of heterogeneous B(OiPr)3-MCM-41 and homogeneous B(OiPr)3, B(OEt)3 catalysts for chemoselective MPV reductions of unsaturated aldehydes and ketones

Applied Catalysis A General ◽

10.1016/j.apcata.2012.06.004 ◽

2012 ◽

Vol 435-436 ◽

pp. 204-216 ◽

Cited By ~ 18

Author(s):

Burcu Uysal ◽

Birsen S. Oksal

Keyword(s):

Unsaturated Aldehydes ◽

Aldehydes And Ketones ◽

Mcm 41

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Theoretical Insight into the Reversal of Chemoselectivity in Diels-Alder Reactions of α,β-Unsaturated Aldehydes and Ketones Catalyzed by Brønsted and Lewis Acids

Organics ◽

10.3390/org2010004 ◽

2021 ◽

Vol 2 (1) ◽

pp. 38-49

Author(s):

Lakhdar Benhamed ◽

Sidi Mohamed Mekelleche ◽

Wafaa Benchouk

Keyword(s):

Lewis Acids ◽

Major Product ◽

Diels Alder ◽

Unsaturated Ketone ◽

Unsaturated Aldehydes ◽

Aldehydes And Ketones ◽

Theoretical Insight ◽

Insight Into ◽

Good Agreement

Experimentally, a reversal of chemoselectivity has been observed in catalyzed Diels–Alder reactions of α,β-unsaturated aldehydes (e.g., (2E)-but-2-enal) and ketones (e.g., 2-hexen-4-one) with cyclopentadiene. Indeed, using the triflimidic Brønsted acid Tf2NH as catalyst, the reaction gave a Diels–Alder adduct derived from α,β-unsaturated ketone as a major product. On the other hand, the use of tris(pentafluorophenyl)borane B(C6F5)3 bulky Lewis acid as catalyst gave mainly the cycloadduct of α,β-unsaturated aldehyde as a major product. Our aim in the present work is to put in evidence the role of the catalyst in the reversal of the chemoselectivity of the catalyzed Diels–Alder reactions of (2E)-but-2-enal and 2-Hexen-4-one with cyclopentadiene. The calculations were performed at the ωB97XD/6-311G(d,p) level of theory and the solvent effects of dichloromethane were taken into account using the PCM solvation model. The obtained results are in good agreement with experimental outcomes.

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