Asymmetric Activation of Chiral Alkoxyzinc Catalysts by Chiral Nitrogen Activators for Dialkylzinc Addition to Aldehydes: Super High-Throughput Screening of Combinatorial Libraries of Chiral Ligands and Activators by HPLC-CD/UV and HPLC-OR/RIU Systems

Mikami, Kōichi; Angelaud, Rémy; Ding, Kuiling; Ishii, Akihiro; Tanaka, Akito; Sawada, Naotaka; Kudo, Kenichi; Senda, Masaaki

doi:10.1002/1521-3765(20010202)7:3<730::aid-chem730>3.3.co;2-t

Cited by 14 publications

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“…Modern advanced asymmetric catalysis demands both maximum efficiency in terms of yield and enantioselectivity and minimal waste derived from catalysts, reagents, solvents, salts, etc. , Catalytic enantioselective dialkylzinc addition to aldehydes is one of the most important reactions involving carbon−carbon bond formation, in which optically active secondary alcohols are obtained as synthetically and pharmaceutically useful compounds . To date, numerous efficient chiral ligands such as amino alcohols ( N , O -ligands), diamines ( N , N -ligands), and diols ( O , O -ligands) have been developed. − We can classify organometal alkylation into three types: (a) double activation by only Lewis acidic organometal reagents, (b) double activation by a Lewis acid−Lewis base, and (c) double activation by a conjugate Lewis acid−Lewis base (Figure ). Usually, organomagnesium and organoaluminum reagents belong to type a.…”

Section: Introductionmentioning

confidence: 99%

3,3‘-Diphosphoryl-1,1‘-bi-2-naphthol−Zn(II) Complexes as Conjugate Acid−Base Catalysts for Enantioselective Dialkylzinc Addition to Aldehydes

2006

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A highly enantioselective dialkylzinc (R(2)(2)Zn) addition to a series of aromatic, aliphatic, and heteroaromatic aldehydes (5) was developed based on conjugate Lewis acid-Lewis base catalysis. Bifunctional BINOL ligands bearing phosphine oxides [P(=O)R(2)] (7), phosphonates [P(=O)(OR)(2)] (8 and 9), or phosphoramides [P(=O)(NR(2))(2)] (10) at the 3,3'-positions were prepared by using a phospho-Fries rearrangement as a key step. The coordination of a NaphO-Zn(II)-R(2) center as a Lewis acid to a carbonyl group in a substrate and the activation of R(2)(2)Zn(II) with a phosphoryl group (P=O) as a Lewis base in the 3,3'-diphosphoryl-BINOL-Zn(II) catalyst could promote carbon-carbon bond formation with high enantioselectivities (up to >99% ee). Mechanistic studies were performed by X-ray analyses of a free ligand (7) and a tetranuclear Zn(II) cluster (21), a 31P NMR experiment on Zn(II) complexes, an absence of nonlinear effect between the ligand (7) and Et-adduct of benzaldehyde, and stoichiometric reactions with some chiral or achiral Zn(II) complexes to propose a transition-state assembly including monomeric active intermediates.

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Section: Introductionmentioning

confidence: 99%

3,3‘-Diphosphoryl-1,1‘-bi-2-naphthol−Zn(II) Complexes as Conjugate Acid−Base Catalysts for Enantioselective Dialkylzinc Addition to Aldehydes

2006

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“…Intense research efforts employing (BINOLate)TiX 2 catalysts have resulted in development of an impressive number of highly enantioselective processes, − , including the cyanosylation of aldehydes, Diels−Alder cycloadditions, − hetero Diels−Alder cycloaddition, − carbonyl−ene reaction, − Mukaiyama aldol condensation, , nitro−aldol condensation, ,, allylation of aldehydes − and ketones, , asymmetric sulfide oxidation, and asymmetric addition of alkyl groups to aldehydes, to name a few. − Despite the remarkable versatility and enantioselectivity of the titanium−BINOL-derived catalysts, investigations into the structure of these species and their reaction mechanisms have been scarce. The very features that make the titanium−BINOL and related titanium−diol systems , efficient catalysts, such as the kinetic lability of titanium alkoxide ligands and the Lewis acidic nature of the titanium center, also complicate mechanistic studies.…”

Section: Introductionmentioning

confidence: 99%

Insight into the Mechanism of the Asymmetric Addition of Alkyl Groups to Aldehydes Catalyzed by Titanium−BINOLate Species

et al. 2002

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The asymmetric addition of alkyl groups to aldehydes catalyzed by BINOLate-titanium complexes has become the testing grounds to evaluate the potential of new BINOL-based ligands. We have investigated the mechanism of this reaction and report our findings here. Model systems for the open form of the catalyst, (BINOLate)[Ti(O-i-Pr)(3)](2), based on mono-oxygen-alkylated BINOL ligands have been examined. Comparison of the reactivity and enantioselectivity of the mono-alkyl BINOL derivatives with those of BINOL indicate that the open form of the catalyst, (BINOLate)[Ti(O-i-Pr)(3)](2), is not active in the asymmetric addition reaction. Several BINOLate-titanium complexes have been synthesized and characterized by X-ray crystallography. These include the dinuclear (BINOLate)Ti(O-i-Pr)(2).Ti(O-i-Pr)(4), which contains a bridging naphtholate and isopropoxy group, trinuclear (BINOLate)Ti(O-i-Pr)(2).[Ti(O-i-Pr)(4)](2), and trimeric [(BINOL)Ti(O-i-Pr)(2)](3). The solid-state and solution structures reported here indicate that (BINOLate)Ti(O-i-Pr)(2) prefers to bind to titanium tetraisopropoxide rather than to itself, explaining why no nonlinear effects are observed in the catalytic reaction. Additionally, experimental evidence suggests that the BINOLate-titanium species responsible for the catalytic and stoichiometric asymmetric addition reactions are different, indicating that the proposed intermediate, (BINOLate)Ti(R)(aldehyde)(O-i-Pr), is not involved in either of these processes. Reactions were examined using different sources of the alkyl group [ZnMe(2) or MeTi(O-i-Pr)(3)]. Under similar conditions, it was found that the product ee's were the same, independent of whether ZnMe(2) or Me-Ti(O-i-Pr)(3) was used as the source of the alkyl groups. This indicates that the role of the dialkylzinc is not to add the alkyl group to the carbonyl but rather to transfer the alkyl group to titanium. On the basis of these results, we hypothesize that the intermediate in the asymmetric addition involves (BINOLate)Ti(O-i-Pr)(2)(aldehyde).MeTi(O-i-Pr)(3).

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“…124 It also induced only modest enantioselectivity during the reaction of lithiated α-(arylthio)benzyl precursors with electrophiles (ee 12-16%), 125 and in the α-methylation of isochromane (ee 5%). 140,141 Several miscellaneous examples of enantioselective reactions mediated by (Ϫ)-sparteine merit brief mention. 128 Other examples of asymmetric deprotonations induced by (Ϫ)-sparteine in combination with organolithium bases include the following: deprotonation and electrophilic trapping of tert-butyl(phenyl)phosphine-borane 129 and aryldimethylphosphine-borane complexes (ee 75-99%); 130 asymmetric lithiation and substitution of various arenetricarbonylchromium() complexes to form planar chiral products (ee up to 92%); 131 and the deprotonation and silylation of terminal epoxides.…”

Section: Stereoselective Transformations Mediated By (؊)-Sparteinementioning

confidence: 99%

Indolizidine and quinolizidine alkaloids

Michael

2002

Nat. Prod. Rep.

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This review covers the isolation, structure determination, synthesis and biological activity of indolizidine and quinolizidine alkaloids from microbial, plant and animal sources. Included in the review are slaframine; hydroxylated indolizidines and their analogues; alkaloids from ants and amphibians; metabolites of the genera Prosopis, Streptomyces and Nuphar and the Lythraceae; phenanthroindolizidines and related alkaloids; lupin alkaloids; and alkaloids from sponges. tunicates and coccinellid beetles. The literature from July 2000 to June 2001 is reviewed, and 172 references are cited.

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Asymmetric Activation of Chiral Alkoxyzinc Catalysts by Chiral Nitrogen Activators for Dialkylzinc Addition to Aldehydes: Super High-Throughput Screening of Combinatorial Libraries of Chiral Ligands and Activators by HPLC-CD/UV and HPLC-OR/RIU Systems

Cited by 14 publications

References 0 publications

3,3‘-Diphosphoryl-1,1‘-bi-2-naphthol−Zn(II) Complexes as Conjugate Acid−Base Catalysts for Enantioselective Dialkylzinc Addition to Aldehydes

3,3‘-Diphosphoryl-1,1‘-bi-2-naphthol−Zn(II) Complexes as Conjugate Acid−Base Catalysts for Enantioselective Dialkylzinc Addition to Aldehydes

Insight into the Mechanism of the Asymmetric Addition of Alkyl Groups to Aldehydes Catalyzed by Titanium−BINOLate Species

Indolizidine and quinolizidine alkaloids

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