In Search of New Approaches to Asymmetric Conjugate Addition: Screening Studies on the Use of [Zn(bpy*)X(R)] Reagents and α,β-Unsaturated Amide Michael Acceptors

2007 ◽  
Vol 72 (8) ◽  
pp. 1107-1121 ◽  
Author(s):  
Alexander J. Blake ◽  
Daniela Giunta ◽  
Jonathan Shannon ◽  
Maurizio Solinas ◽  
Francesca Walzer ◽  
...  
Keyword(s):  
Ligand Exchange ◽  
Conjugate Addition ◽  
Nmr Studies ◽  
Conjugate Additions ◽  
New Approaches ◽  
Michael Acceptors ◽  
Derivatives Of ◽  
Moderate Yield ◽  
C Nmr

Conjugate additions of [Zn(bpy*)Cl(Et)] (bpy* = 4,4'-di-tert-butyl-2,2'-bipyridine) to cyclohex-2-en-1-one are promoted by ZnMe2 in 88% ee but in moderate yield under CuI phosphoramidite catalysis. In the absence of ZnMe2 the [Zn(bpy*)Cl(Et)] is inactive indicating a Schlenk-type equilibrium. Other derivatives of [Zn(bpy*)Cl(R)] (R = Bu, 4-methylbenzyl), prepared in situ from [ZnCl(R)] and the bipyridine give low yields due to competing chloride abstraction. 13C NMR studies indicate facile organo-ligand exchange between [Zn(bpy*)(Et)2] and [Zn(bpy*)Cl2] complexes. In the presence of the bipyridine, [ZnBr(allyl)] disproportionates into [Zn(bpy*)Br2] and [Zn(bpy*)(allyl)2] species. In separate studies, simple (E)-MeCH=CHCONMeR (R = Me, OMe) α,β-unsaturated amides undergo asymmetric 1,4-addition of EtMgBr in 75-99% yield and 48-79% ee in the presence of the diphosphines JosiPhos or MeDuPhos and copper(I) sources.

ChemInform Abstract: In Search of New Approaches to Asymmetric Conjugate Addition: Screening Studies on the Use of [Zn(bpy*)X(R)] Reagents and α,β-Unsaturated Amide Michael Acceptors.

ChemInform ◽  
2008 ◽  
Vol 39 (2) ◽  
Author(s):  
Alexander J. Blake ◽  
Daniela Giunta ◽  
Jonathan Shannon ◽  
Maurizio Solinas ◽  
Francesca Walzer ◽  
...  
Keyword(s):  
Conjugate Addition ◽  
New Approaches ◽  
Michael Acceptors

Tricarbonylferrole iron tricarbonyl derivatives: formation from thiophenes and iron atoms in a CO atmosphere and fluxional behaviour

1977 ◽  
Vol 55 (20) ◽  
pp. 3509-3514 ◽  
Author(s):  
Tristram Chivers ◽  
Peter L. Timms
Keyword(s):  
Nmr Studies ◽  
Warm Up ◽  
Metal Atoms ◽  
Iron Tricarbonyl ◽  
Derivatives Of ◽  
C Nmr

Co-condensation of metal atoms (Cr, Fe) with thiophenes [Formula: see text] (R = R′ = H, Me; R = H, R' = Me) at −196 °C leads to desulphurization of the thiophene. Warm-up of the iron–thiophene co-condensate in a CO atmosphere produces derivatives of tricarbonylferrole iron tricarbonyl, C4H2RR′Fe2(CO)6. 13C nmr studies of these complexes show that the tricarbonyl ferrole unit is static from −95 °C to +60 °C, while the π-Fe(CO)3 group exhibits fluxional behaviour. Addition of dienes or Me3P in hexane to the iron–thiophene co-condensate at −196 °C yields thermally unstable red solutions on melting.

Seven-coordinate metal carbonyl derivatives of cis-(CH3)2AsC(CF3)=C(CF3)As(CH3)2

1976 ◽  
Vol 54 (16) ◽  
pp. 2548-2556 ◽  
Author(s):  
William R. Cullen ◽  
Lynn M. Mihichuk
Keyword(s):  
Metal Carbonyl ◽  
Activation Parameters ◽  
Nmr Studies ◽  
H Nmr ◽  
Carbonyl Derivatives ◽  
Derivatives Of ◽  
C Nmr

The seven-coordinate complexes (L—L)M(CO)3X2 (M = Mo, W; X = Br, I; (L—L) = cis-(CH3)2AsC(CF3)=C(CF3)As(CH3)2) were prepared and characterized. 1H and 13C nmr studies at 25 and −70 °C suggest that the complexes are nonrigid. Similarly 1H nmr studies indicate the seven-coordinate (L—L)LMo(CO)2Br2 complexes are also nonrigid. The (L—L)L2Mo(CO)Br2 complexes (L is a monodentate phosphite or phosphine) are rigid at 25 °C and nonrigid at higher temperatures. Activation parameters are calculated for the motion of two of the complexes and possible mechanisms are discussed.

scholarly journals Synthesis, Characterisation and Hydrolytic Reactions of the First Pentaisopropoxostannate Derivatives of Magnesium, Zinc and Cadmium

2007 ◽  
Vol 2007 (8) ◽  
pp. 458-460
Author(s):  
Jayshree Shahanl ◽  
Anirudh Singh
Keyword(s):  
Molecular Weight ◽  
Nmr Studies ◽  
Molar Ratios ◽  
Derivatives Of ◽  
C Nmr

Pentaisopropoxostannate derivatives of the types [{M[Sn(OPri)5](μ–Cl)}2] and [M{Sn(OPri)5}2] have been prepared by the reactions of MCl2 (M = Mg, Zn, and Cd) with NaSn(OPri)5 in 1:1 and 1:2 molar ratios, respectively, in benzene. All these derivatives have been characterised by elemental and isopropoxo group analyses, spectroscopic (IR, 1H and 13C NMR) studies, and molecular weight determinations. Two typical hydrolytic reactions of [Zn{Sn(OPri)5}2] have also been investigated.

Chiral Amine-Mediated Asymmetric Conjugate Additions to Vinyl Sulfones

2009 ◽  
Vol 62 (9) ◽  
pp. 951 ◽  
Author(s):  
Qiang Zhu ◽  
Yixin Lu
Keyword(s):  
Organic Synthesis ◽  
Recent Progress ◽  
Conjugate Addition ◽  
Chiral Molecules ◽  
Conjugate Additions ◽  
Chiral Amine ◽  
Michael Acceptors

Chiral molecules containing sulfone groups are useful intermediates and have found wide applications in organic synthesis. In this account, recent progress in the use of vinyl sulfones as Michael acceptors in the asymmetric organocatalytic conjugate addition is summarized.

Identification des configurations relatives d'alcools secondaires α-cyclopropylidéniques et α-vinylcyclopropaniques. Attribution de structure aux éthyl-6 diméthyl-2,4 oxa-3 bicyclo [3.1.01,5]hexanes

1979 ◽  
Vol 57 (17) ◽  
pp. 2314-2320 ◽  
Author(s):  
Maurice Vincens ◽  
Claude Dumont ◽  
Michel Vidal
Keyword(s):  
Basic Medium ◽  
Secondary Alcohols ◽  
Nmr Studies ◽  
Derivatives Of ◽  
C Nmr

During a stereochemical study of α-cyclic secondary alcohols, the relative configurations of the E, R*, and S* isomers of 1-(2-ethyl-3-ethylidene(1R*,2R*)cyclopropyl)ethanol was determined. Treatment in a basic medium of these secondary diastereomeric alcohols leads to the R* and S* isomers of 1-(2-ethyl-3-vinyl(1R*,2S*,3S*)cyclopropyl)ethanol. Cyclic oxymercuration of these cyclopropanoic derivatives yields the di-endo, di-exo, and exo–endo derivatives of 6-ethyl-2,4-dimethyl-3-oxabicyclo[3.1.0.1,5]hexane. The determination of the structure as bicyclic ethers, based on ir and 1H and 13C nmr studies, permits the assignment of the relative configurations of the vinylcyclopropanoic and cyclopropylidene alcohols. [Journal translation]

New approaches for Mars in-situ resource utilization based on the reverse water gas shift

1997 ◽  
Author(s):  
Robert Zubrin ◽  
Mitchell Clapp ◽  
Tom Meyer ◽  
Robert Zubrin ◽  
Mitchell Clapp ◽  
...  
Keyword(s):  
Resource Utilization ◽  
Water Gas Shift ◽  
New Approaches ◽  
Reverse Water Gas Shift ◽  
Water Gas

Thermal cyclocondensations of 3-N(4- and 5-benzimidazolyl and benztriazolyl)amino derivatives of 2-propenoic acid

1987 ◽  
Vol 52 (12) ◽  
pp. 2918-2925 ◽  
Author(s):  
Viktor Milata ◽  
Dušan Ilavský
Keyword(s):  
Uv Spectra ◽  
Propenoic Acid ◽  
Amino Derivatives ◽  
Derivatives Of ◽  
C Nmr ◽  
Ir And Uv Spectra

The cyclization of 3-N(4- and 5-benzimidazolyl and benztriazolyl)amino-2-cyano- and 2-ethoxycarbonyl-2-propenoate esters Ia, b-IVa, b under the conditions of the Gould-Jacobs reaction leads to angularly ring-fused substituted imidazo or triazolo[4,5-f] (V, VI) and [4,5-h] (VII, VIII) quinolines, respectively. The esters Vb-VIIIb have been transformed into the corresponding chloroderivatives Vc-VIIIc. 3-N(5-Benzimidazolyl and 5-benztriazolyl)amino-2-cyano-2-propenenitriles are cyclized in the presence of aluminium(III) chloride to give the aminoquinolines Vd, VId. The structure of the products has been characterized by their 1H, 13C NMR, IR, and UV spectra.

Mechanistische Untersuchungen zum reversiblen Gleichgewicht von metallorganischen Tripeldecker- und Sandwichkomplexen des Typs [Bis{(η5-CpR)Co}-μ-{η4:η4-aren}] und [(η5-CpR)Co(η6-aren)] / Mechanistic Studies towards the Reversible Equilibrium between Metal Organic Triple Decker and Sandwich Complexes [Bis{(η5 -CpR)Co}-μ-{η4 :η4-arene}] and [{(η5-CpR)Co(η6-arene)]

1998 ◽  
Vol 53 (11) ◽  
pp. 1267-1272 ◽  
Author(s):  
Jörg J. Schneider ◽  
Dirk Wolf
Keyword(s):  
Ligand Exchange ◽  
Sandwich Complexes ◽  
Valuable Metal ◽  
H Nmr ◽  
Synthetic Utility ◽  
Metal Organic ◽  
Arene Ligand ◽  
Benzene Toluene

The arene ligand exchange mechanism of slipped arene triple deckers [Bis{(η5-CpR)Co}-μ-{η4:η4-arene}] (R = Me5, 1,2,4 tri-tert butyl, arene = benzene, toluene) 1 was studied by 1H-NMR spectroscopy for different concentrations and solvents. It has been found that triple deckers of type 1 decompose slowly in solution. A unique equilibrium, between these triple deckers and the mixed sandwich complexes [(η6-arene)Co(η5-CpR)] and 14 e [(η5-Cp)Co]solv fragments generated in situ by decomposition o f 1 exists. In addition to this equilibrium arene lability of the thus formed mixed sandwich complex type has been detected by NMR making slipped triple deckers 1 ideal single source compounds for the generation of two [(η5-Cp)Co] fragments in one reaction step. Such fragments are valuable metal ligand components with high synthetic utility in organometallic chemistry.

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