Copper Reagents Research Articles

An Enantioselective Total Synthesis of (-)-Stemoamide

An enantioselective synthesis of (-)-stemoamide has been achieved in 14 steps starting from pyroglutamyl alcohol in ca. 7% overall yield. The key steps in the strategy are a conjugate addition of a vinyl copper reagent and a ring closing metathesis (RCM) reaction to form the seven-membered ring.

Consecutive double 1,2-migration of two different groups in silyl(dichloromethyl)cuprates.

Very different reactivity of two types of cuprates: Treatment of a silyldichloromethyllithium compound with a copper reagent prepared from BuMgBr and CuCN gives the product of consecutive dibutylation. On the other hand, Bu2CuLi⋅LiCN affords the butylation/cyanation product (see scheme, Si=Ph2MeSi).

The use of a chiral borate counteranion as a 1H NMR shift reagent for cationic copper(I) complexes

The chiral borate counteranion bis[(R)-1,1′-bi-2-naphtholato]borate (1–) has been found to be a competent chiral 1H NMR shift reagent for cationic copper(I) complexes. This has been demonstrated by the addition of the Cu(NCMe)4+ salt of 1– to two classes of common chiral ligands in asymmetric catalysis: 2,2′-bis(di-p-tolylphosphino)-1,1′-binaphthyl (tol-BINAP) (2) and 2,2′-isopropylidenebis(4-phenyl-2-oxazoline) (3). In the case of ligand 2, the addition of 1 equiv. of either (R,R)-2 or (S,S)-2 to Cu(NCMe)4+1– results in well-resolved 1H NMR resonances for the two enantiomers. Examination of standard solutions of non-enantiopure 2 shows that the copper complex can be an effective NMR shift reagent of a wide range of enantiomeric compositions. Cu(NCMe)4+1– also generates distinct 1H NMR resonances for the two separate enantiomers of 2,2′-isopropylidenebis(4-phenyl-2-oxazoline) (3). However, attempts to employ this copper salt as a chiral NMR shift reagent for rac-3 led to the discovery of a new and unexpected equilibrium: [(R,R)-3]Cu+ + [(S,S)-3]Cu+ [Formula: see text] [(R,R)-3][(S,S)-3]Cu+ + Cu+. Key words: chiral counteranion, copper, chiral NMR shift reagent, ion pairing.

Copper Reagents: A New and Efficient Solution for the Selective Addition of Metalated Propargylic Amines to Aldehydes.

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Chiral lithiothiophenes as non-transferable ligands in organocuprate conjugate addition reactions

Non-transferable carbon bound homochiral ligands have been developed for the asymmetric transfer of an alkyl or an aryl group to a prochiral α,β-unsaturated enone with copper reagents. These ligands are based on thiophene and chiral amino alcohols derived from l-proline and ephedrine.

Highly Stereoselective anti SN2′ Substitutions of (Z)‐Allylic Pentafluorobenzoates with Polyfunctionalized Zinc—Copper Reagents.

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The remarkable ability of lithium ion to reverse the stereoselectivity in the conjugate addition of Li[BuCuI] to a chiral N-crotonyl-2-oxazolidinone.

[reaction: see text] The influence of lithium ions on the conjugate addition of the monoorganocuprate reagent, Li[BuCuI], to a chiral crotonate has been investigated. The results show that iodotrimethylsilane (TMSI) is crucial for the asymmetric conjugate addition of the copper reagent, but only in THF or when 12-crown-4 is used. The reaction is thought not to involve any halosilane in any critical steps in the organocopper mechanisms conducted in Et(2)O.

Highly anti‐Selective SN2′ Substitutions of Chiral Cyclic 2‐Iodo‐allylic Alcohol Derivatives with Mixed Zinc—Copper Reagents.

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Copper reagents: a new and efficient solution for the selective addition of metallated propargylic amines to aldehydes.

[reaction: see text] Anti alpha-amino-homopropargylic alcohols are prepared by addition of metallated propargylic amines to aldehydes. Among the four organometallic (LI, Zn, Ti, Cu) derivatives used, the most effective are the copper reagents.

The first conjugate addition reaction of terminal alkynes catalytic in copper: conjugate addition of alkynes in water.

We document that alkynyl copper reagents generated under aqueous conditions from terminal acetylenes, catalytic Cu(OAc)2, and sodium ascorbate undergo additions to Meldrum's acid-derived Michael acceptors at room temperature (Scheme 1). The additions are not only novel, but also constitute the first example of the conjugate addition reaction of an acetylide catalytic in copper.

Structure of Self-assembled Magnetic FePtCu Nanoparticles Arrays

AbstractIn this study, a series of FexPtyCu100-x-y nanoparticles were chemically synthesized by solution-phase reduction of platinum and copper reagents and thermal decomposition of iron pentacarbonyl in the presence of stabilizers oleic acid and oleyl amine. As-prepared particles had a chemically disordered face-centered cubic (fcc) lattice with an average diameter of 3.5 nm. The particle size, and the corresponding size distribution were controlled by varying the organic surfactant (oleic acids, etc.), its concentration, and the reaction temperature. These particles were well dispersed in hydrocarbon solvents and self-assembled into two or three dimensions particles arrays with a variety of closepacking arrangements. Domain of monolayers, bilayers and multilayers of particles arrays were frequently detected in TEM specimens. Both cubic close-packed (ccp) and honeycomb arrays were also uniquely observed. It was also demonstrated that the controlled organic surfactant layer (organic capping) play a crucial role in determining assembly dimensions and symmetry as well as particle packing arrays.

An Attempt for Biaryl Coupling Reaction of Benzyl Benzoate Derivatives under Ullmann Conditions

The biaryl coupling reaction of benzyl benzoate derivatives (3) and (4) was examined with copper(0) reagent. A dimerized product (9) was mainly obtained whereas the desired intramolecularly coupled product (11) was not detected when 3 was employed as the substrate. On the other hand, the reaction of 4 afforded a small amount of the desired lactone (14) although the main product was the dimerized 12.

Alkylation of 4‐Substituted 1‐Acetoxy‐2‐cyclopentenes by Using Copper Reagents Derived from Alkylmagnesium Halides and Copper(I) Cyanide.

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Regio‐ and Stereo‐Controlled Copper Organometallic Addition to a Piperidinyl Aziridine: Synthesis of trans 3‐Amino‐4‐alkyl‐piperidines.

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ChemInform Abstract: The Preparation of Nonracemic Secondary α‐(Carbamoyloxy)alkylzinc and Copper Reagents. A Versatile Approach to Enantioenriched Alcohols.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Recent Advances in Ullmann Reaction:Copper ( II ) Diacetate C at alysed N - ,O - and S - ArylationInvolving Polycoordinate Hetero atomic Derivatives

Copper-catalyzed O- and N-arylation reactions involving triarylbismuth diacetates or aryllead triacetates are ligand coupling reactions which were discovered in the eighties independently by Bartons and Dodonovs groups. These reagents lead generally to efficient arylation under mild neutral conditions (room temperature or 40 dgree C, no added basic reagent). Recently, the scope of these main group metal mediated reactions was broadened when Chan and Evans reported that organoboron compounds can be used as the source of the organic aryl ligand. Subsequently, organosiloxanes, organostannanes and diaryliodonium salts proved also to be efficient reagents for these mild copper catalyzed O- and N-arylation reactions. Organoantimony compounds were also used but appeared to be less efficient reagents. Keywords: ullmann reaction, polycoordinate derivative, organosiloxane, organostannanes, diaryliodonium

Alkylation of 4-substituted 1-acetoxy-2-cyclopentenes by using copper reagents derived from alkylmagnesium halides and copper(I) cyanide

Alkylation of the acetates derived from 4-phenyl- and 4-butyl-2-cyclopenten-1-ols 2 was investigated with copper reagents derived from n-BuMgX (X=Cl, Br) and CuCN in 2:1 and 1:1 ratios in THF and in Et 2O. cis 1,4-Isomers 4a, b (R=Ph, n-Bu) were produced regioselectively from the corresponding trans acetates 3a, b with the reagent in a 2:1 ratio of BuMgCl and CuCN in THF, while the BuMgBr-based reagents of 2:1 and 1:1 ratios in Et 2O furnished cis 3,4-isomers 5a, b . A similar tendency was obtained with cis acetates 6a, b (R=Ph, n-Bu).

Regio- and stereo-controlled copper organometallic addition to a piperidinyl aziridine: synthesis of trans 3-amino-4-alkyl-piperidines

3,4-Piperidinyl aziridine N-phosphonate underwent ring opening in Grignard addition catalyzed by a copper reagent to yield trans 3-amino-4-alkyl-piperidines. The nucleophilic addition occurred trans to the aziridine group and regioselectively at C-4 position of the piperidine ring. The high regioselectivity was rationalized by steric argument based on conformational analysis.

New Aspects of Organocopper Reagents: 1,3- and 1,2-Chiral Induction and Reaction Mechanism

Recent advances in chemo-, regio- and stereoselective reactions of α,β-unsaturated carbonyl compounds with organocoppers and their trifluoroborane complexes are described. Organocopper-Lewis acid reagents are utilized in many key steps for the synthesis of medicinally important natural products. Transition-state models have been proposed to explain the observed regio- and stereochemistries. 1. Introduction 2. Reductive Cleavage by means of Organocopper Reagents 3. Organocyanocopper-Lewis Acid Mediated 1,3-Chirality Transfer of Acyclic (E)-γ-Mesyloxy-α,β-enoates. 3.1 Synthesis of α-Alkyl-β,γ-enolates with High Optical Purity 3.2 (E)-Alkene Dipeptide Isostere Synthesis 3.3 Will Methylcopper Reagents React with γ,δ-Epoxy(E)-α,β-Unsaturated Esters in the Same Manner? 3.4 Determination of Stereochemistry at the α-Position to the Carboxy Group by Circular Dichroism 4. "Higher Order" Zinc Cuprates: The Latest Copper Reagent for the 1,3-Chirality Transfer 5. Rationale of 1,2-Chiral Induction in the Conjugate Addition to γ-Alkoxy α,β-Unsaturated Systems 6. Conclusion

Transmetalation of palladium enolate and its application in palladium-catalyzed homocoupling of alkynes: a room-temperature, highly efficient route to make diynes.

A novel pathway for the homocoupling reaction has been achieved using a similar protocol as the cross-coupling reaction. Ethyl bromoacetate is chosen to initiate the coupling reaction through oxidative addition to a Pd(0) species, and an PdBr(enolate) intermediate is formed. This intermediate can undergo double transmetalation with an alkynyl copper reagent, and reductive elimination produces a variety of diynes in high yields.