Highly Enantioselective Aerobic Oxidation of α-Hydroxyphosphonates Catalyzed by Chiral Vanadyl(V) Methoxides Bearing <i>N</i>-Salicylidene-α-aminocarboxylates

Pawar, Vijay D.; Bettigeri, Sampada V.; Weng, Shao-Hsing; Kao, Jun-Qi; Chen, Chien‐Tien

doi:10.1021/ja060639o

Cited by 118 publications

(43 citation statements)

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“…The oxidative kinetic resolution strategy has also shown its potential in the syntheses of biologically relevant a-hydroxy phosphonates, [8] a-hydroxy ketones [9] , enantioenriched cyclic ethers [10] and an antitumor agent -octalactin A.…”

Section: Introductionmentioning

confidence: 99%

Asymmetric Aerobic Oxidation of α‐Hydroxy Acid Derivatives Catalyzed by Reusable, Polystyrene‐Supported Chiral N‐Salicylidene Oxidovanadium tert‐Leucinates

Salunke¹,

Babu²,

Chen³

2011

Adv Synth Catal

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Abstract:The direct immobilization of two different C-5-propargyl ether-modified, chiral N-salicylidene vanadyl(V) tert-leucinates onto 4-azidomethylsubstituted polystyrene by click chemistry was examined. Among the eight different solvents investigated, the resulting polystyrene-supported catalysts promote the asymmetric, aerobic oxidation of a-hydroxy (thio)esters and amides with enantioselectivities of up to 99% ee (selectivity factor up to 41) in chloroform. These polystyrene-supported catalysts can be readily recovered by filtration and reused for at least four consecutive runs without discernible loss of reactivity and enantioselectivity.Keywords: click chemistry; direct immobilization; enantioselective aerobic oxidation; recyclable catalysts; vanadyl compounds Transition metal complex-catalyzed asymmetric aerobic oxidations [1] have recently emerged as highly efficient methods to obtain optically pure alcohols along with kinetic resolution, especially in cases where asymmetric reduction of ketones could not provide sufficiently high enantioselectivity. Significant progress in this area has been made with a variety of chiral metal catalysts.[2] In particular, enantiomerically pure a-hydroxy carboxylic acid and mandelic acid derivatives are ubiquitous building blocks in enantioselective synthesis and the synthesis of biologically active compounds such as semi-synthetic penicillin, cephalosporin, anti-thrombotic and anti-obesity agents.[3] With the extension of interest in new organic transformations by using vanadyl species, [4,5] we and Tostes group have developed highly enantioselective aerobic oxidations catalyzed by chiral N-salicylidene vanadyl(V) carboxylates [6] and alocholates, [7] respectively, for the preparation of optically enriched a-hydroxy carboxylic acid derivatives. The oxidative kinetic resolution strategy has also shown its potential in the syntheses of biologically relevant a-hydroxy phosphonates, [8] a-hydroxy ketones [9] , enantioenriched cyclic ethers [10] and an antitumor agent -octalactin A.[11] Moreover, chiral vanadyl(V) complexes are also an effective catalysts in asymmetric sulfide oxidation [12] and oxidative coupling of 2-naphthols. [13] In addition, these complexes acts as a DNA photocleavage agent [14] and metal ion-specific (e.g., K + and Ag + ) transporters. [15] Although these homogenous transition metal complexes offer high levels of reactivity and enantioselectivity, their applications in the chemical and pharmaceutical industry remain somewhat limited due to their relatively high cost, difficulties in separation and contamination of metal complexes or metal salts either in waste or the end products. Consequently, their immobilization on solid supports has attracted enormous interest, as this allows for facile separation of the heterogeneous catalysts from products, enables efficient recovery and reuse of catalysts and minimizes pollution occurring from metal complexes.[16] Despite these options and numerous applications of chiral vanadium complexes, only a few approache...

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Section: Introductionmentioning

confidence: 99%

Asymmetric Aerobic Oxidation of α‐Hydroxy Acid Derivatives Catalyzed by Reusable, Polystyrene‐Supported Chiral N‐Salicylidene Oxidovanadium tert‐Leucinates

Salunke¹,

Babu²,

Chen³

2011

Adv Synth Catal

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“…In most substrates, high k rel values ranging from 10 to > 100 are obtained. Complex 8 can be also applied to asymmetric aerobic oxidation of α -hydroxyphosphonic acid derivatives, which are attractive targets in medicinal chemistry (Scheme 11.15 ) [27] . Various dibenzyl α -hydroxy phosphonates bearing aryl or vinyl substituent at the α -position are effectively resolved, generally with excellent selectivity ( k rel > 99).…”

Section: Vanadium Catalystmentioning

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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“…The reaction can run in the absence of an amine to give, in good yields, hydroxyphosphonates (77) [72][73][74][75] which cannot be converted into aminophosphonates.…”

Section: Hydrophosphorylationmentioning

confidence: 99%

Phosphorylation of Thiophenes

Ivonin¹,

Tolmachev²,

Пинчук³

2008

COC

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This review deals with synthetic methods, chemical transformations, and some physical properties of thienyland benzothienyl substituted phosphorus compounds bearing P-Het or P-CH 2 -Het bonds.The basic synthetic approaches to these compounds include reactions of metalated thiophenes with phosphorus(III) and (V) halides, phosphorylation of thiophenes in the presence of a mild Lewis acid, use of halogenothiophenes in the Arbuzov reaction, and phosphorylation of thiophenes with phosphorus(III) halides in basic medium. Synthetic approaches to condensed heterocyclic systems of novel types are also considered.Investigation of chemical properties of phosphorylated thiophenes has revealed that, despite the great similarity with phenyl analogues, differences connected to the nature of the heterocycle are observed. The tertiary phosphines bearing at least one thienyl substituent are less active in quaternization and oxidation reactions. At the same time, basic hydrolysis leading to C-P bond cleavage is facilitated, as compared to benzene derivatives.

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Highly Enantioselective Aerobic Oxidation of α-Hydroxyphosphonates Catalyzed by Chiral Vanadyl(V) Methoxides Bearing N-Salicylidene-α-aminocarboxylates

Abstract: An unprecedented vanadyl(V) methoxide complex 4 derived from 3,5-dibromo-N-salicylidene-l-tert-leucinate enables highly enantioselective aerobic oxidations of alpha-hydroxyphosphonates at ambient temperature with selectivity factors ranging from 3 to >99.

Cited by 118 publications

References 20 publications

Asymmetric Aerobic Oxidation of α‐Hydroxy Acid Derivatives Catalyzed by Reusable, Polystyrene‐Supported Chiral N‐Salicylidene Oxidovanadium tert‐Leucinates

Asymmetric Aerobic Oxidation of α‐Hydroxy Acid Derivatives Catalyzed by Reusable, Polystyrene‐Supported Chiral N‐Salicylidene Oxidovanadium tert‐Leucinates

Asymmetric Oxidations and Related Reactions

Phosphorylation of Thiophenes

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