Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

NHC-Cu-catalyzed protoboration of monosubstituted allenes. Ligand-controlled site selectivity, application to synthesis and mechanism.

ABSTRACT: Two types of NHC-Cu complexes catalyze protoborations of terminal allenes to afford valuable 1,1- or trisubstituted vinylboron species with high site selectivity and stereoselectivity. The scope of the method, application to natural product synthesis, and mechanistic basis for the observed selectivity trends are presented.

SUBMITTER: Meng F

PROVIDER: S-EPMC3625862 | biostudies-literature | 2013 Mar

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

NHC-Cu-catalyzed protoboration of monosubstituted allenes. Ligand-controlled site selectivity, application to synthesis and mechanism.

Meng Fanke F Jung Byunghyuck B Haeffner Fredrik F Hoveyda Amir H AH

Organic letters 20130305 6

Two types of NHC-Cu complexes catalyze protoborations of terminal allenes to afford valuable 1,1- or trisubstituted vinylboron species with high site selectivity and stereoselectivity. The scope of the method, application to natural product synthesis, and mechanistic basis for the observed selectivity trends are presented. ...[more]

PMID: 23461762

Similar Datasets

Platinum(II)-catalyzed intermolecular hydroamination of monosubstituted allenes with secondary alkylamines.

Project description:A 1:1 mixture of (dppf)PtCl(2) and AgOTf (5 mol%) catalyzed the intermolecular hydroamination of monosubstituted allenes with secondary alkylamines at 80 degrees C to form allylic amines in good yield with selective formation of the E-diastereomer.

| S-EPMC2924659 | biostudies-literature

Synthesis of cross-conjugated trienes by rhodium-catalyzed dimerization of monosubstituted allenes.

Project description:A rhodium(I)/dppe catalyst promoted dimerization of monosubstituted allenes in a stereoselective manner to give cross-conjugated trienes, which are different from those obtained by a palladium catalyst.

| S-EPMC3107559 | biostudies-literature

Ligand-Controlled Regioselective Copper-Catalyzed Trifluoromethylation To Generate (Trifluoromethyl)allenes.

Project description:"Cu-CF3" species have been used historically for a broad spectrum of nucleophilic trifluoromethylation reactions. Although recent advancements have employed ligands to stabilize and harness the reactivity of this key organometallic intermediate, the ability of a ligand to differentiate a regiochemical outcome of a Cu-CF3-mediated or -catalyzed reaction has not been previously reported. Herein, we report the first example of a Cu-catalyzed trifluoromethylation reaction in which a ligand controls the regiochemical outcome. More specifically, we demonstrate the ability of bipyridyl-derived ligands to control the regioselectivity of the Cu-catalyzed nucleophilic trifluoromethylation reactions of propargyl electrophiles to generate (trifluoromethyl)allenes. This method provides a variety of di-, tri-, and tetrasubstituted (trifluoromethyl)allenes, which can be further modified to generate complex fluorinated substructures.

| S-EPMC4433581 | biostudies-other

Vicinal diboronates in high enantiomeric purity through tandem site-selective NHC-Cu-catalyzed boron-copper additions to terminal alkynes.

Project description:A Cu-catalyzed protocol for conversion of terminal alkynes to enantiomerically enriched diboronates is reported. In a single vessel, a site-selective hydroboration of an alkyne leads to the corresponding terminal vinylboronate, which undergoes a second site-selective and enantioselective hydroboration. Reactions proceed in the presence of 2 equiv of commercially available bis(pinacolato)diboron [B(2)(pin)(2)] and 5-7.5 mol % loading of a chiral bidentate imidazolinium salt, affording diboronates in 60-93% yield and up to 97.5:2.5 enantiomeric ratio (er). The enantiomerically enriched products can be functionalized to afford an assortment of versatile organic molecules. Enynes are converted to unsaturated diboronates with high chemo- (>98% reaction of alkyne; <2% at alkene) and enantioselectivity (e.g., 94.5:5.5 er).

| S-EPMC2797564 | biostudies-literature

Site- and enantioselective formation of allene-bearing tertiary or quaternary carbon stereogenic centers through NHC-Cu-catalyzed allylic substitution.

Project description:Catalytic enantioselective allylic substitutions that result in addition of an allenyl group (<2% propargyl addition) and formation of tertiary or quaternary C-C bonds are described. Commercially available allenylboronic acid pinacol ester is used. Reactions are promoted by a 5.0-10 mol % loading of sulfonate-bearing chiral bidentate N-heterocyclic carbene (NHC) complexes of copper, which exhibit the unique ability to furnish chiral products arising from the S(N)2' mode of addition. Allenyl-containing products are generated in up to 95% yield, >98% S(N)2' selectivity, and 99:1 enantiomeric ratio (er). Site-selective NHC-Cu-catalyzed hydroboration of enantiomerically enriched allenes and conversion to the corresponding ?-vinyl ketones demonstrates the method's utility.

| S-EPMC3267425 | biostudies-literature

Scope and mechanism of the Pt-catalyzed enantioselective diboration of monosubstituted alkenes.

Project description:The Pt-catalyzed enantioselective diboration of terminal alkenes can be accomplished in an enantioselective fashion in the presence of chiral phosphonite ligands. Optimal procedures and the substrate scope of this transformation are fully investigated. Reaction progress kinetic analysis and kinetic isotope effects suggest that the stereodefining step in the catalytic cycle is olefin migratory insertion into a Pt-B bond. Density functional theory analysis, combined with other experimental data, suggests that the insertion reaction positions platinum at the internal carbon of the substrate. A stereochemical model for this reaction is advanced that is in line both with these features and with the crystal structure of a Pt-ligand complex.

| S-EPMC3805123 | biostudies-literature

Ligand-controlled cobalt-catalyzed regiodivergent hydroboration of aryl,alkyl-disubstituted internal allenes.

Project description:We report a stereoselective regiodivergent hydroboration of aryl,alkyl-disubstituted internal allenes with pinacolborane (HBpin) in the presence of cobalt catalysts generated from bench-stable Co(acac)2 and bisphosphine ligands. An interesting correlation between the regioselectivity of this hydroboration and the bite angles of bisphosphine ligands was identified. When hydroboration was conducted with cobalt catalysts containing bisphosphines with medium bite angles (e.g. 98° for dppb and 96° for dppf), HBpin was selectively added to the alkyl-substituted double bond. However, HBpin was selectively added to the aryl-substituted double bond when the reactions were conducted with cobalt catalysts containing bisphosphines with large bite angles (e.g. 111° for xantphos and 114° for Nixantphos). A range of internal allenes underwent these Co-catalyzed hydroboration reactions in a regiodivergent manner to yield the corresponding (Z)-alkenylboronates in high isolated yields and with high regioselectivity. These reactions show good functional group compatibility and can be readily scaled up to gram scales without using a dry box. In addition, the comparison of regioselectivity between the Co-catalyzed hydrosilylation and hydroboration reactions of the same allene substrate suggests that this Co-catalyzed regiodivergent hydroboration of allenes proceeds through a Co-Bpin intermediate. Deuterium-labeling experiments suggest that the Co-Bpin intermediates react with allenes to form allylcobalt species which then react with HBpin to release (Z)-alkenylboronate products.

| S-EPMC8157611 | biostudies-literature

NHC-Cu-catalyzed addition of propargylboron reagents to phosphinoylimines. Enantioselective synthesis of trimethylsilyl-substituted homoallenylamides and application to the synthesis of S-(-)-cyclooroidin.

Project description:A catalytic method for the efficient and enantioselective addition of a 1-trimethylsilyl-substituted allene moiety to phosphinoylimines is presented. Transformations are promoted by 5.0 mol % of a copper complex of an N-heterocyclic carbene in the presence of a propargylboron reagent that can be readily prepared in multigram quantities. Within 10 min of reaction, products are obtained in up to 91% yield, 98% allene (vs propargyl) selectivity, and 98:2 enantiomeric ratio. An assortment of aldimines serve as suitable substrates. The phosphinoyl and silyl groups can be removed efficiently and orthogonally. The silylallene moiety may be transformed to versatile derivatives that are difficult to access via nonsilylated allenes. The special features and utility of the approach are highlighted through a succinct enantioselective synthesis of marine alkaloid S-(-)-cyclooroidin.

| S-EPMC3954525 | biostudies-literature

A Computational Investigation of the Ligand-Controlled Cu-Catalyzed Site-Selective Propargylation and Allenylation of Carbonyl Compounds.

Project description:A copper-catalyzed site-selective propargylation/allenylation reaction toward carbonyl compounds has been mechanistically investigated using a computational approach. Different reaction pathways and catalytic cycles were investigated. Control of the site selectivity arises from a destabilizing interaction introduced by the phenyl-substituted ligand.

| S-EPMC5718194 | biostudies-literature

Accelerating the insertion reactions of (NHC)Cu-H <i>via</i> remote ligand functionalization.

Project description:Most ligand designs for reactions catalyzed by (NHC)Cu-H (NHC = N-heterocyclic carbene ligand) have focused on introducing steric bulk near the Cu center. Here, we evaluate the effect of remote ligand modification in a series of [(NHC)CuH]2 in which the para substituent (R) on the N-aryl groups of the NHC is Me, Et, t Bu, OMe or Cl. Although the R group is distant (6 bonds away) from the reactive Cu center, the complexes have different spectroscopic signatures. Kinetics studies of the insertion of ketone, aldimine, alkyne, and unactivated α-olefin substrates reveal that Cu-H complexes with bulky or electron-rich R groups undergo faster substrate insertion. The predominant cause of this phenomenon is destabilization of the [(NHC)CuH]2 dimer relative to the (NHC)Cu-H monomer, resulting in faster formation of Cu-H monomer. These findings indicate that remote functionalization of NHCs is a compelling strategy for accelerating the rate of substrate insertion with Cu-H species.

| S-EPMC8409461 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data