Dinuclear chiral vanadium catalysts for oxidative coupling of 2-naphthols via a dual activation mechanism

Takizawa, Shinobu; Katayama, Tomomi; Sasai, Hiroaki

doi:10.1039/b806016a

Cited by 109 publications

(50 citation statements)

References 78 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Related to Gong's catalyst 26, Sasai and coworkers [54][55][56][57] described dinuclear vanadium (IV) catalyst (R a ,S,S)-29, which was prepared in a similar procedure as to that of 26, demonstrated much more different reactivity for promoting the oxidative coupling reaction of 2-naphthols 27 (Scheme 14). An ESR study revealed no V-O-V linkage in the structure of (R a ,S,S)-29.…”

Section: -50mentioning

confidence: 95%

See 1 more Smart Citation

Recent advances in asymmetric oxidative coupling of 2‐naphthol and its derivatives

Wang

2010

Chirality

122

View full text Add to dashboard Cite

show abstract

Section: -50mentioning

confidence: 95%

“…The two amino moieties in the catalyst affect the enantiocontrol of the coupling and the binaphthyl backone assists in aligning the two 2-naphthols with each other for the oxidative coupling. 57 Intermolecular manner coupling proceeds as a minor pathway.…”

Section: -50mentioning

confidence: 99%

Recent advances in asymmetric oxidative coupling of 2‐naphthol and its derivatives

Wang

2010

Chirality

122

View full text Add to dashboard Cite

show abstract

“…Concentration and chromatography (hexane/etherϭ15/1) gave (R)-9 with 52% ee (0. 3 ), 62% ee) in acetone (4 ml) was added under reflux a solution of potassium permanganate (0.50 g, 3.17 mmol) in hot water (4 ml). After reflux for 1.5 h, the mixture was treated with 10% HCl (2 ml) and sodium bisulfite at room temperature, and then extracted with CHCl 3 (15 mlϫ3 (R)-1,1-Binaphthalene-2-carboxylic Acid BHA Ester ((؊)-(R)-9 with 62% ee) A mixture of above 1,1Ј-binaphthalene-2-carboxylic acid (83.9 mg, 0.28 mmol), pyridine (1 drop), and thionyl chloride (2 ml) was refluxed for 1.5 h, and then concentrated to afford acid chloride (0.11 g) as a yellow oil (IR (KBr): 1780).…”

Section: Methodsmentioning

confidence: 99%

Asymmetric Construction of Binaphthyl by the Chiral Diether-Mediated Conjugate Addition of Naphthyllithium to Naphthalenecarboxylic Acid 2,6-Di-t-butyl-4-methoxyphenyl Ester

Shindo

Yamamoto

Yamada

et al. 2009

CHEMICAL & PHARMACEUTICAL BULLETIN

View full text Add to dashboard Cite

Asymmetric construction of axial chirality represented by biaryl has been the continuing interest of organic chemistry. 1)Coupling of two naphthyl groups is the fundamental strategy for the formation of chiral biaryl bond by using chiral partner(s) or chiral mediator. Practical level of asymmetric oxidative coupling of naphthols to chiral binaphthol has been demonstrated by Nakajima et al.2,3) Transition metal-catalyzed formation of axial chirality has been proven to be in the reasonably high level of efficiency. 4,5) Other interesting way is the application of conjugate addition of naphthylmetals to chiral naphthyl acceptors and subsequent elimination process as has been demonstrated by Meyers and Lutomski,6) Wilson and Cram, 7) and Miyano and colleagues. 8) We have also developed an efficient asymmetric conjugate additionelimination of 1-napthyllithium 3 and fluoronaphthylimine 2 giving chiral binaphthyls 4 and 5 with 91% ee by setting the external chiral diether ligand 1 9,10) (5 mol%)-catalyzed methodology as shown in Chart 1.11) As part of the continuing approach toward conjugate addition-elimination protocol, we selected a naphthyl ester as a directing group in place of an imine. 12) We describe herein the comparison of two approaches to axial chirality of binaphthyl by using asymmetric conjugate addition of 1-naphthyllithium 3 to naphthalenecarboxylic acid BHA (2,6-di-t-butyl-4-methoxyphenol) ester 6 under the steric control of chiral diether 1.Asymmetric conjugate addition reaction of 3 to 6 is controlled by a chiral diether 1-chelated complex to give addition intermediate 7 as an initial product. Protonation would give us a chiral addition product 8 if X (ϭH) is not a leaving group (Chart 2). Subsequent oxidative aromatization of 8 is the way to binaphthyl to give target 9. Another way is the asymmetric conjugate addition and subsequent elimination of a leaving group X from 7 to give the target 9 in a one pot. It is important to point out that the central chirality in 7 and 8 should be transferred or converted to axial chirality of 9 in both of two approaches.Asymmetric Conjugate Addition and Subsequent Oxidative Aromatization to Binaphthyl We began our studies with two-step procedure, that is, asymmetric conjugate addition and subsequent oxidative aromatization to binaphthyl. The reaction of 3 eq of 3 with naphthalenecarboxylic acid BHA ester (6a) in the presence of 3.3 eq of diether ligand 1 in a mixture of toluene and diethyl ether at Ϫ45°C for 5 h gave, after protonation of an intermediate enolate 7a (XϭH) with trifluoroacetic acid, a 1 : 1 olefin isomeric mixture of addition products 8 in 66% yield (Chart 3). Since the subsequent in situ treatment of an enolate 7a successively with super-hydride, methyl iodide, and finally sodium borohydride has been confirmed to give an alcohol 10 with 95% enantiomeric excess (ee) in 40% yield, 13) the adducts 8 should have 95% enantiomeric purity. The central chirality in 8 was then transferred by treating with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) in ref...

show abstract

“…Although we independently developed dinuclear vanadium(IV) catalysts and dinuclear vanadium(V) catalysts for enantioselective oxidative coupling of 2-naphthols, [44][45][46][47][48] the preparation procedure for dinuclear vanadium(IV) catalysts is similar to that of Gong's catalysts [66][67][68] except for the use of 2.0-2.2 eq of vanadyl sulfate in EtOH-tetrahydrofuran (THF)-H 2 O for the complexation. Even though the absolute configurations of the components of the catalysts are the same, the absolute configurations of the major products were opposite to each other (Table 5).…”

Section: Comparison Of Our Dinuclear Vanadium(iv) and (V) Catalysts Wmentioning

confidence: 99%

“…43) This review presents our recent research on development of chiral dinuclear vanadium complexes which work as dual activation catalysts for oxidative coupling of 2-naphthols. [44][45][46][47][48] The synthesis of optically pure 1,1Ј-bi-2-naphthol (BINOL) derivatives is of importance because these moieties are used as chiral ligands and auxiliaries for a wide range of organic functional transformations. 49,50) Catalytic asymmetric preparation of BINOL systems has continued to attract the attention of many researchers.…”

mentioning

confidence: 99%

Development of Dinuclear Vanadium Catalysts for Enantioselective Coupling of 2-Naphthols via a Dual Activation Mechanism

Takizawa

2009

CHEMICAL & PHARMACEUTICAL BULLETIN

Self Cite

View full text Add to dashboard Cite

Catalytic asymmetric reactions are among the most powerful synthetic methods to obtain optically active compounds.1,2) Recent challenges focus on the development of asymmetric catalysts for carbon-carbon bond-forming reactions with high activity and broad substrate generality, which lead to practical, efficient, and environmentally benign chemical syntheses. Dual activation systems for substrates such as nucleophiles and electrophiles lead to enhanced reaction rates and more specific control of the transition structure with respect to the catalyst's asymmetric environment. Dual activation catalyses can be classified into three categories ( Fig. 1): Type 1) dual activation using two different kinds of catalysts [3][4][5][6][7][8][9][10][11][12] ; Type 2) conjugated-type dual activation with a functional group such as a phosphate which has both acidic and basic sites in one functionality [13][14][15] ; and Type 3) dual activation by two catalytic sites in a single catalyst. For efficient dual activation of the substrates, a balance between these two functionalities in the catalyst is required. For example, in an acid-base type catalyst the selfquenching reaction of acidic and basic moieties on the catalyst can lead to its inactivation.We postulated that a chiral complex possessing two identical metal centers in a single molecule, which could activate two substrates simultaneously in a homolytic coupling reaction of 2-naphthol molecules, would enhance the reaction rate with high enantioselectivity. To achieve the new dual activation catalysis in an oxidative coupling reaction, we designed the catalyst (R a ,S,S)-1 42) bearing two active sites attached to a binaphthyl skeleton, taking advantage of the activation entropy (Fig. 2). Activation entropy strongly con- Development of Dinuclear Vanadium Catalysts for Enantioselective Coupling of 2-Naphthols via a Dual Activation MechanismShinobu TAKIZAWA This review describes our recent efforts in the development of chiral dinuclear vanadium complexes which work as dual activation catalysts for oxidative coupling of 2-naphthols. A chiral dinuclear vanadium(IV) complex (R a ,S,S)-1a possessing (S)-tert-leucine moieties at the 3,3 -positions of the (R)-binaphthyl skeleton was developed, and found to promote oxidative coupling of 2-naphthol to afford (S)-1,1 -bi-2-naphthol (BINOL) with 91% ee. To verify the dual activation mechanism, mononuclear vanadium(IV) complex (S)-10 was also prepared. Kinetic analysis revealed that the reaction rate of oxidative coupling of 2-naphthol promoted by (R a ,S,S)-1a is 48.3 times faster than that of (S)-10. In the coupling reaction, the two vanadium metals in the chiral complex activate two molecules of 2-naphthol simultaneously achieving a high reaction rate with high enantiocontrol. Since the dinuclear vanadium(IV) complex was found to be readily oxidized to afford a corresponding vanadium(V) species during preparation in air, a new synthetic procedure using VOCl 3 and a convenient one-pot procedure using VOSO 4 under O 2 have been applie...

show abstract

Dinuclear chiral vanadium catalysts for oxidative coupling of 2-naphthols via a dual activation mechanism

Cited by 109 publications

References 78 publications

Recent advances in asymmetric oxidative coupling of 2‐naphthol and its derivatives

Recent advances in asymmetric oxidative coupling of 2‐naphthol and its derivatives

Asymmetric Construction of Binaphthyl by the Chiral Diether-Mediated Conjugate Addition of Naphthyllithium to Naphthalenecarboxylic Acid 2,6-Di-t-butyl-4-methoxyphenyl Ester

Development of Dinuclear Vanadium Catalysts for Enantioselective Coupling of 2-Naphthols via a Dual Activation Mechanism

Contact Info

Product

Resources

About