Stereoselective Copper Research Articles

Copper (I)-catalyzed ‘Quick Click’ generated 1,2,3-triazole anthraquinone linkers for selective detection of Fe (II) ions

The current report describes a fast and high yielding synthesis of 1,4-dihydroxyanthraquinone based 1,2,3-triazole linkers T1 and T2 through a stereoselective Copper (I) – catalyzed alkyne azide cycloaddition (CuAAC) reaction and their sensing behavior for the selective detection of Fe(II) ions by UV–Visible spectroscopy. UV–Visible absorption studies were performed using 0.5 mM solution of testing probes in 4:1 acetonitrile/water (v/v) solvent with a set of metal ions such as Mn (II), Cd (II) Hg (II), Ni (II), Pb (II), Zn (II), Fe (II), Fe (III), Ce (III), Cr (III), Co (II), Ba (II), K (I) and Na (I). The significant change in absorption spectrum was observed for both the probes with the addition of Fe (II) ions. The spectrograms recorded with the successive increase in concentration of Fe (II) ions from 0.013 mM to 0.14 mM shows isosbestic points at two particular wavelengths along with an observable blue shift of 4 nm and 7 nm in between the isosbestic points for probes T1 and T2 respectively and the limit of detection of 10 µM for triazole derivative T1, where as it is 9.3 µM for T2.

Copper(I)-catalyzed Stereoselective Defluoroborylation of Aliphatic Gem-Difluoroalkenes

This study reports a method for the stereoselective copper(I)-catalyzed defluoroborylation of aliphatic gem-difluoroalkenes to afford (Z)-monofluoro-substituted borylalkenes. Gem-difluoroalkenes bearing a variety of functional groups were efficiently borylated with high stereoselectivity. A theoretical study of the reaction mechanism is also described.

ChemInform Abstract: Regio‐ and Stereoselective Copper(II)‐Catalyzed Hydrosilylation of Activated Allenes in Water: Access to Vinylsilanes.

By using catalytic amounts of copper(II), 4-picoline, and dimethylphenylsilylpinacol borane, a series of allenoates were silylated on the β carbon in good to excellent yields and high (E)-selectivity. The mild and efficient silylation method is conducted in water under atmospheric conditions to afford vinylsilanes.

ChemInform Abstract: Chemo‐, Regio‐, and Stereoselective Copper(II)‐Catalyzed Boron Addition to Acetylenic Esters and Amides in Aqueous Media.

AbstractThe use of unsymmetrical diboron reagent pinBBdan (II) allows a mild and efficient copper(II)‐catalyzed β‐borylation of alkynoates to give the functionalized acrylates (III) in good yield.

Regio- and Stereoselective Copper(II)-Catalyzed Hydrosilylation of Activated Allenes in Water: Access to Vinylsilanes.

By using catalytic amounts of copper(II), 4-picoline, and dimethylphenylsilylpinacol borane, a series of allenoates were silylated on the β carbon in good to excellent yields and high (E)-selectivity. The mild and efficient silylation method is conducted in water under atmospheric conditions to afford vinylsilanes.

ChemInform Abstract: Copper(I)‐Y Zeolite‐Catalyzed Regio‐ and Stereoselective [2 + 2 + 2] Cyclotrimerization Cascade: An Atom‐ and Step‐Economical Synthesis of Pyrimido[1,6‐a]quinoline.

AbstractThis regio‐ and stereoselective copper(I)‐Y zeolite‐catalyzed termolecular [2+2+2]/[NC+CC+NC] cycloaddition cascade reaction involves two molecules of the in situ generated N‐sulfonylketenimines and quinoline to afford functionalized pyrimidoquinolines.

Homogeneous and Stereoselective Copper(II)-Catalyzed Monohydration of Methylenemalononitriles to 2-Cyanoacrylamides

A facile and efficient route for the homogeneous and highly stereoselective monohydration of substituted methylenemalononitriles to (E)-2-cyanoacrylamides catalyzed by copper(II) acetate monohydrate in acetic acid containing 2% water is described, and a mechanism is proposed. The protocol has proved to be suitable for the monohydration of dicyanobenzenes and 2-substituted malononitriles.

ChemInform Abstract: Regioselective and Stereoselective Copper(I)‐Promoted Allylation and Conjugate Addition of N‐Boc‐2‐lithiopyrrolidine and N‐Boc‐2‐lithiopiperidine.

AbstractThe reactions allow formation of 2‐substituted pyrrolidines and piperidines as useful precursors of alkaloids such as norhygrine (IV) and coniine (XVII).

Regioselective and Stereoselective Copper(I)-Promoted Allylation and Conjugate Addition of N-Boc-2-lithiopyrrolidine and N-Boc-2-lithiopiperidine

Copper salts have been screened for transmetalation and electrophilic quench of N-tert-butoxycarbonyl-2-lithiopyrrolidine (N-Boc-2-lithiopyrrolidine) and N-Boc-2-lithiopiperidine, formed by deprotonation of N-Boc-pyrrolidine and N-Boc-piperidine, respectively. Transmetalation with zinc chloride then (lithium chloride solubilized) copper cyanide followed by allylation typically gives mixtures of regioisomers (S(N)2 and S(N)2' products), whereas transmetalation with copper iodide.TMEDA then allylation occurs regioselectively (S(N)2 mechanism). Addition to an enone or alpha,beta-unsaturated ester occurs by 1,4-addition. Asymmetric deprotonation of N-Boc-pyrrolidine or dynamic resolution in the presence of a chiral ligand of N-Boc-2-lithiopiperidine followed by the zinc/copper chemistry was successful and gave the allylated pyrrolidine and piperidine products with good enantioselectivity, although use of the copper iodide chemistry resulted in some loss of enantiopurity. The chemistry provides formal syntheses of (+)-allosedridine, (+)-lasubine II, and (+)-pseudohygroline and has been used for the synthesis of (+)-coniine, (-)-pelletierine, (+)-coniceine, (-)-norhygrine, and the ant extract alkaloids cis- and trans-2-butyl-5-propylpyrrolidine.

Highly Regio‐ and Stereoselective Copper(I) Chloride‐Mediated Carbometallation of 2,3‐Allenols with Grignard Reagents.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Highly Regio‐ and Stereoselective Copper(I) Chloride‐Mediated Carbometallation of 2,3‐Allenols with Grignard Reagents

AbstractAn efficient highly regio‐ and stereoselective copper(I) chloride‐mediated carbometallation of differently substituted 2,3‐allenols with primary or secondary alkyl or aromatic Grignard reagents followed by iodination to synthesize fully‐substituted allylic alcohols has been developed. This protocol introduces the R4 group from the Grignard reagent to the terminal position of the 2,3‐allenols.

Chiral Allylic Cyanohydrins as Versatile Substrates for Diastereoselective Copper(I)-mediated SN2′ Allylic Substitutions

2,6-Difluorobenzoated derivatives bearing a protected cyanohydrin function undergo highly stereoselective copper(I)-mediated SN2′ allylic substitution reactions with diorganozinc reagents leading to chiral unsaturated nitriles.

Structure Identification of Precatalytic Copper Phosphoramidite Complexes in Solution

1+1 is more than 2: A binuclear copper phosphoramidite precatalyst with mixed trigonal/tetrahedral coordination environments (see picture) is proposed based on NMR spectroscopy, mass spectrometry, and elemental analysis. The precatalyst represents a new structural motif for stereoselective copper catalysts and explains ligand acceleration and salt sensitivity in highly enantioselective 1,4-additions to enones.

Asymmetric Michael Addition Using N‐Cinnamoyl‐ and N‐Crotonyl‐trans‐hexahydrobenzoxazolidin‐2‐ones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Asymmetric Michael addition using N-cinnamoyl- and N-crotonyl- trans-hexahydrobenzoxazolidin-2-ones

Preparation of N-cinnamoyl- and N-crotonyl-oxazolidin-2-ones 2 and 3 or ent - 2 and ent - 3 from (4 S,5 S)- and (4 R,5 R)- trans-hexahydrobenzoxazolidin-2-ones 1 or ent - 1 are reported. Stereoselective copper promoted conjugated additions of Grignard reagents to chiral N-enoyl amides 2 and 3 or ent - 2 and ent - 3 in the presence of Zn(II) salts afforded the 1,4-addition products 4– 11 and the corresponding enantiomers.

New efficient and totally stereoselective copper allylic benzoyloxylation of sterol derivatives

A new efficient and totally stereoselective copper allylic benzoyloxylation of sterol derivatives has been developed. This methodology has been successfully applied to the synthesis of 7α-hydroxy DHEA and 7α-hydroxy cholesterol in a two-step synthesis with high chemical yields (77% and 61% overall yield, respectively). A mechanistic rationale justifying the total stereoselectivity encountered has been proposed.

Asymmetric synthesis of cis-2,4-disubstituted azetidin-3-ones from metal carbene chemistry

Several chiral cis-2,4-disubstituted azetidin-3-ones were prepared as single diastereoisomers from N-protected amino acids, employing a highly stereoselective copper carbenoid N–H insertion reaction of diazoketones. These azetidin-3-ones were then converted into fully substituted azetidines in a few steps in good to high yields.

A stereoselective synthesis of the C(1)–C(16) fragment of the bryostatins

A synthesis of the C(1)–C(16) fragment of the brysostatins has been developed. Key steps are the stereoselective copper(I) catalysed addition of allylmagnesium bromide to an alkynyl ester, a condensation of a βγ-unsaturated aldehyde with a ketophosphonate, and the formation of the B-ring under mild conditions by stereoselective intramolecular conjugate addition.

Asymmetric hydroboration with new chiral monoalkylboranes bearing a non-stereogenic, chirotopic center

Enantiomerically pure 2,5-diorganocyclopentanecarboxylic acids bearing a non-stereogenic, chirotopic center were prepared via stereoselective copper catalyzed carbon-carbon bond forming reactions. These compounds serve as intermediates in the synthesis of new chiral monoalkylboranes which lead to enantio-selectivities of up to 64% ee in the asymmetric hydroboration of cyclic olefins.

Synthesis of the AB spiroketal subunit of spongistatin 1 (altohyrtin A): The Pyrone approach

The synthesis of the AB spiroketal fragment of spongistatin 1 (altohyrtin A) has been accomplished utilizing the addition of a metalated pyrone to an aldehyde followed by acid catalyzed spirocyclization. A stereoselective copper ( I) promoted conjugate addition of vinylmagnesium bromide was used to establish the C11 stereogenic center.