Enantioselective Baeyer–Villiger Oxidation Catalyzed by Palladium(II) Complexes with Chiral <i>P,N</i>-Ligands

Malkov, Andrei V.; Friscourt, Frédéric; Bell, Mark; Swarbrick, Martin E.; Kočovský, Pavel

doi:10.1021/jo800246g

Cited by 76 publications

(27 citation statements)

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“…[29,30] Chemical catalysts offer an attractive alternative, especially reactions using environmentally benign oxidants such as H 2 O 2 , but they are still limited in number and are often less enantioselective than their biological counterparts. [5] Since the first reports on metal-catalyzed asymmetric B-V reactions in 1994, [31] various chiral metal catalysts based on Cu II , [32] Pt II , [33] Ti IV , [34] Co III , [35] Zr IV , [36] Mg II , [37] Al III , [38] and Pd II [39] have been developed in recent years for this transformation. However, so far, very few of them could attain enantioselectivity at a level comparable to enzymes, and wide substrate generality has not yet been achieved in each case.…”

mentioning

confidence: 99%

Mechanistic Investigation of Chiral Phosphoric Acid Catalyzed Asymmetric Baeyer–Villiger Reaction of 3‐Substituted Cyclobutanones with H₂O₂ as the Oxidant

Wang

et al. 2010

Chemistry A European J

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The mechanism of the chiral phosphoric acid catalyzed Baeyer-Villiger (B-V) reaction of cyclobutanones with hydrogen peroxide was investigated by using a combination of experimental and theoretical methods. Of the two pathways that have been proposed for the present reaction, the pathway involving a peroxyphosphate intermediate is not viable. The reaction progress kinetic analysis indicates that the reaction is partially inhibited by the gamma-lactone product. Initial rate measurements suggest that the reaction follows Michaelis-Menten-type kinetics consistent with a bifunctional mechanism in which the catalyst is actively involved in both carbonyl addition and the subsequent rearrangement steps through hydrogen-bonding interactions with the reactants or the intermediate. High-level quantum chemical calculations strongly support a two-step concerted mechanism in which the phosphoric acid activates the reactants or the intermediate in a synergistic manner through partial proton transfer. The catalyst simultaneously acts as a general acid, by increasing the electrophilicity of the carbonyl carbon, increases the nucleophilicity of hydrogen peroxide as a Lewis base in the addition step, and facilitates the dissociation of the OH group from the Criegee intermediate in the rearrangement step. The overall reaction is highly exothermic, and the rearrangement of the Criegee intermediate is the rate-determining step. The observed reactivity of this catalytic B-V reaction also results, in part, from the ring strain in cyclobutanones. The sense of chiral induction is rationalized by the analysis of the relative energies of the competing diastereomeric transition states, in which the steric repulsion between the 3-substituent of the cyclobutanone and the 3- and 3'-substituents of the catalyst, as well as the entropy and solvent effects, are found to be critically important.

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confidence: 99%

Mechanistic Investigation of Chiral Phosphoric Acid Catalyzed Asymmetric Baeyer–Villiger Reaction of 3‐Substituted Cyclobutanones with H₂O₂ as the Oxidant

Wang

et al. 2010

Chemistry A European J

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“…Prochiral cyclobutanones (1) were oxidized at low temperature (À40 C), with 5 mol % catalyst loading and the urea-H 2 O 2 complex as the stoichiometric oxidant to give lactones 2 in good yields and up to 81% ee (Eq. (10.5)) [50]. All these complexes are active towards meso or chiral cyclobutanone substrates 1, which are significantly more reactive than the larger cyclic ketones.…”

Section: Chemocatalytic Versionsmentioning

confidence: 96%

Oxidation of Carbonyl Compounds

Johnston¹,

Bäckvall²

2010

Modern Oxidation Methods

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“…The complete enantioselectivity was achieved in the reaction of a tricyclic ketone. Recently, Malkov and Ko č ovsk ý also reported chiral terpene -derived P , N -ligands for the palladium -catalyzed reaction, and a good enantioselectivity of up to 81% ee was observed in the reaction of 3 -substituted cyclobutanones [127] . Metal -free, enzyme -catalyzed reactions are also effective methods for the BaeyerVilliger reactions, and many developments have been reported [128] .…”

Section: Asymmetric Baeyer -Villiger Oxidationmentioning

confidence: 99%

Asymmetric Oxidations and Related Reactions

Matsumoto

Katsuki

2010

Catalytic Asymmetric Synthesis

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GENERAL INTRODUCTIONOxidation is a fundamental technology for converting bulk chemicals into valuable materials and is also a useful tool for sophisticated functionalization of organic molecules. Thus, intensive research efforts have been devoted to the development of selective and practical oxidation methods, and a wide variety of chiral metal -based catalysts and organocatalysts have been developed for catalytic asymmetric oxidation reactions in industry and academia in the last half -century [1] . In contrast to the rapid improvement in stereoselectivity, the enhancement of atom economy [2] falls behind. While atom effi ciency (especially active oxygen content in oxygenation reactions) of stoichiometric oxidants is a factor that should be considered, most of the catalytic asymmetric oxidations still use conventional stoichiometric oxidants of low atomeffi ciency such as peracids, alkyl hydroperoxides, hypervalent iodine reagents, hypochlorite, and N -oxide compounds (Table 11.1 ). The use of such oxidants causes the formation of large amounts of undesirable waste. From the viewpoint of ecological sustainability, oxidation with a higher atom -effi cient, safe, abundant, and preferably inexpensive oxidant is favorable. Considering the requirements, molecular oxygen and hydrogen peroxide are the oxidants of choice [3] . Molecular oxygen offers a large advantage because it is abundant in air and is inexpensive. Aerobic oxidation that directly uses ambient air as an oxidant is similar to respiration in living organisms. Hydrogen peroxide is also recognized as a green oxidant. It is almost as equally atomeffi cient as molecular oxygen, and the by -product is safe and clean water. Moreover, its aqueous solution (typically 30 -35%) is inexpensive and easy to handle. Consequently, the development of catalytic asymmetric oxidations with molecular oxygen Catalytic Asymmetric Synthesis, Third Edition, Edited by Iwao Ojima

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Enantioselective Baeyer–Villiger Oxidation Catalyzed by Palladium(II) Complexes with Chiral P,N-Ligands

Cited by 76 publications

References 76 publications

Mechanistic Investigation of Chiral Phosphoric Acid Catalyzed Asymmetric Baeyer–Villiger Reaction of 3‐Substituted Cyclobutanones with H₂O₂ as the Oxidant

Mechanistic Investigation of Chiral Phosphoric Acid Catalyzed Asymmetric Baeyer–Villiger Reaction of 3‐Substituted Cyclobutanones with H₂O₂ as the Oxidant

Oxidation of Carbonyl Compounds

Asymmetric Oxidations and Related Reactions

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Enantioselective Baeyer–Villiger Oxidation Catalyzed by Palladium(II) Complexes with Chiral P,N-Ligands

Cited by 76 publications

References 76 publications

Mechanistic Investigation of Chiral Phosphoric Acid Catalyzed Asymmetric Baeyer–Villiger Reaction of 3‐Substituted Cyclobutanones with H2O2 as the Oxidant

Mechanistic Investigation of Chiral Phosphoric Acid Catalyzed Asymmetric Baeyer–Villiger Reaction of 3‐Substituted Cyclobutanones with H2O2 as the Oxidant

Oxidation of Carbonyl Compounds

Asymmetric Oxidations and Related Reactions

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Mechanistic Investigation of Chiral Phosphoric Acid Catalyzed Asymmetric Baeyer–Villiger Reaction of 3‐Substituted Cyclobutanones with H₂O₂ as the Oxidant

Mechanistic Investigation of Chiral Phosphoric Acid Catalyzed Asymmetric Baeyer–Villiger Reaction of 3‐Substituted Cyclobutanones with H₂O₂ as the Oxidant