Showing papers on "Alkylation published in 2006"
TL;DR: The mechanistic aspects considered when designing reactions with DPPBA-based ligands are highlighted and a working model for the a priori prediction of their stereochemical outcome is presented.
Abstract: Palladium-catalyzed asymmetric allylic alkylation has proven to be a powerful method for the preparation of a wide variety of chiral compounds and the rapid assembly of complex molecular architecture from simple starting materials. While many types of catalyst systems have been successfully employed with certain systems, diphenylphosphino benzoic acid (DPPBA) based ligands have found use over a broad range of substrate classes. This Account highlights the mechanistic aspects considered when designing reactions with DPPBA-based ligands and presents a working model for the a priori prediction of their stereochemical outcome.
415 citations
TL;DR: It is demonstrated that substituted benzofurans can be prepared efficiently via a Pd-catalyzed phenol formation/cyclization protocol starting from 2-chloroaryl alkynes.
Abstract: The direct and selective synthesis of phenols from aryl/heteroaryl halides and KOH has been achieved through the use of highly active monophosphine-based catalysts derived from Pd(2)dba(3) and ligands L1 or L2 and the biphasic solvent system 1,4-dioxane/H(2)O We have also demonstrated a one-pot method of phenol formation/alkylation for the preparation of alkyl aryl ethers from aryl halides In many instances, this protocol overcomes limitations in existing Pd-catalyzed coupling reactions of aliphatic alcohols with aryl halides Finally, we demonstrate that substituted benzofurans can be prepared efficiently via a Pd-catalyzed phenol formation/cyclization protocol starting from 2-chloroaryl alkynes
400 citations
TL;DR: The combination of directed C-H activation, batch-wise addition of tetraalkyltin reagents, and rate enhancement by benzoquinone and microwave irradiation provides a promising strategy for the direct coupling of C- H bonds with organometallic reagents.
Abstract: The combination of directed C−H activation, batch-wise addition of tetraalkyltin reagents, and rate enhancement by benzoquinone and microwave irradiation provides a promising strategy for the direct coupling of C−H bonds with organometallic reagents. A variety of tetraalkyltins were coupled to C−H bonds to give the alkylated products in good yields by using 5 mol % Pd(OAc)2 as the catalyst. Benzoquinone was shown to be essential for the C−H activation when substrates containing non-π-conjugated chelating groups are used. Monitoring the formation and reductive elimination of the Pd(Ar)(Me)L2 complex also revealed that benzoquinone promotes the reductive elimination step. Microwave irradiation enhances the reaction rate drastically. The versatility of this protocol was demonstrated by using substrates containing either oxazoline or pyridine as directing groups.
362 citations
TL;DR: An efficient, transition-metal-free procedure for the N-arylation of amines, sulfonamides, and carbamates and O-arylations of phenols and carboxylic acids has been achieved by allowing these substrates to react with a variety of o-silylaryl triflates in the presence of CsF.
Abstract: An efficient, transition-metal-free procedure for the N-arylation of amines, sulfonamides, and carbamates and O-arylation of phenols and carboxylic acids has been achieved by allowing these substrates to react with a variety of o-silylaryl triflates in the presence of CsF. Good to excellent yields of arylated products are obtained under very mild reaction conditions. This chemistry readily tolerates a variety of functional groups.
247 citations
TL;DR: A new protein modification reaction has been developed based on a palladium-catalyzed allylic alkylation of tyrosine residues that provides convenient access to synthetic lipoproteins.
Abstract: A new protein modification reaction has been developed based on a palladium-catalyzed allylic alkylation of tyrosine residues. This technique employs electrophilic pi-allyl intermediates derived from allylic acetate and carbamate precursors and can be used to modify proteins in aqueous solution at room temperature. To facilitate the detection of modified proteins using SDS-PAGE analysis, a fluorescent allyl acetate was synthesized and coupled to chymotrypsinogen A and bacteriophage MS2. The tyrosine selectivity of the reaction was confirmed through trypsin digest analysis. The utility of the reaction was demonstrated by using taurine-derived carbamates as water solubilizing groups that are cleaved upon protein functionalization. This solubility switching technique was used to install hydrophobic farnesyl and C(17) chains on chymotrypsinogen A in water using little or no cosolvent. Following this, the C(17) alkylated proteins were found to associate with lipid vesicles. In addition to providing a new protein modification strategy targeting an under-utilized amino acid side chain, this method provides convenient access to synthetic lipoproteins.
247 citations
TL;DR: This methodology provides a direct way to use allylic sp3 C-H bonds for forming C-C bonds in the presence of an oxidizing reagent, t-BuOOH.
Abstract: A catalytic allylic alkylation was developed via the cross-dehydrogenative-coupling reaction of allylic sp3 C-H and methylenic sp3 C-H catalyzed by copper bromide and cobalt chloride in the presence of an oxidizing reagent, t-BuOOH. This methodology provides a direct way to use allylic sp3 C-H bonds for forming C-C bonds.
239 citations
TL;DR: In this article, the authors present the significant advances which were made in the last decade in the understanding of the transformation over acid and bifunctional zeolite catalysts of the cheap and readily available C2-C4 alkanes into more valuable products: mechanism of activation, reaction scheme, nature of the active sites.
Abstract: This review paper presents the significant advances which were made in the last decade in the understanding of the transformation over acid and bifunctional zeolite catalysts of the cheap and readily available C2–C4 alkanes into more valuable products: mechanism of activation, reaction scheme, nature of the active sites. Both the transformations of pure alkanes: n-butane isomerization, C2–C4 alkane aromatization and of alkanes in mixture with alkenes: isobutane–butene alkylation or with aromatic hydrocarbons: benzene alkylation with ethane or propane are considered.
216 citations
TL;DR: In this paper, the catalytic activity of Bronsted acid sites in zeolites was studied by the monomolecular conversion of propane over zeolite with varying framework topologies and Si/Al ratios.
197 citations
TL;DR: In this article, the electrophilic α-alkylation of ketones with alcohols is accomplished by a hydrogen autotransfer process catalyzed by RuCl 2 (DMSO) 4.
194 citations
TL;DR: This work presents the first examples of Cu-catalyzed enantioselective conjugate additions of alkyl- and arylzinc reagents to unactivated cyclic beta-substituted enones, affording the desired products bearing all-carbon quaternary stereogenic centers in 67-->98% yield and in up to 97% ee.
Abstract: We present the first examples of Cu-catalyzed enantioselective conjugate additions of alkyl- and arylzinc reagents to unactivated cyclic beta-substituted enones. Transformations are promoted in the presence of 2.5-15 mol % of a readily available chiral NHC-based Cu complex, affording the desired products bearing all-carbon quaternary stereogenic centers in 67-->98% yield and in up to 97% ee. Catalytic enantioselective reactions can be carried out on a benchtop, with undistilled solvent and commercially available (not further purified) Cu salts. Mechanistic models, accounting for the observed levels and trends in enantioselectivity are provided.
188 citations
TL;DR: A novel asymmetric Friedel-Crafts alkylation of indoles with nitroalkenes catalyzed by Zn(II)-bisoxazoline complexes has been developed and is synthesized in excellent yields and high enantioselectivities.
Abstract: A novel asymmetric Friedel−Crafts alkylation of indoles with nitroalkenes catalyzed by Zn(II)−bisoxazoline complexes has been developed. The nitroalkylated indoles are synthesized in excellent yields and high enantioselectivities (up to 90% ee). The effects of ligand structure, metal salt, and solvent on the reaction are discussed. The substrates of the reaction can be aromatic, heteroaromatic, and even aliphatic nitroalkenes. The high reactivity and selectivity of the reaction are presumptively attributed to the activation and asymmetric induction of chiral Lewis acids coordinated by nitroalkene substrates through a 1,3-metal bonding model.
TL;DR: A highly efficient alkylation to ketones and aldimines with Grignard reagents in the presence of catalytic trialkylzinc(II) ate complexes derived from ZnCl2 (10 mol %) in situ was developed.
Abstract: A highly efficient alkylation to ketones and aldimines with Grignard reagents in the presence of catalytic trialkylzinc(II) ate complexes derived from ZnCl2 (10 mol %) in situ was developed This simple Zn(II)-catalyzed alkylation could minimize the well-known but serious problems with the use of only Grignard reagents, which leads to reduction and aldol side products, and the yield of desired alkylation products could be improved
Patent•
20 Oct 2006TL;DR: In this article, a method for producing alkylated hydrocarbons is described, in which formation fluid is produced from a subsurface in situ heat treatment process and a liquid stream and a first gas stream are separated to produce at least a second gas stream.
Abstract: A method for producing alkylated hydrocarbons is disclosed. Formation fluid is produced from a subsurface in situ heat treatment process. The formation fluid is separated to produce a liquid stream and a first gas stream. The first gas stream includes olefins. The liquid stream is fractionated to produce at least a second gas stream including hydrocarbons having a carbon number of at least 3. The first gas stream and the second gas stream are introduced into an alkylation unit to produce alkylated hydrocarbons. At least a portion of the olefins in the first gas stream enhance alkylation.
TL;DR: In this paper, the electrophilic β-alkylation of secondary alcohols with primary alcohols is accomplished by a hydrogen autotransfer process catalyzed by RuCl2(DMSO)4.
TL;DR: The chiral Pt catalyst precursor Pt((R,R)-Me-Duphos)(Ph)(Cl) mediated alkylation of racemic secondary phosphines PHR(R') with benzyl halides in the presence of base to give enantioenriched tertiary phosphines PR(R')(CH2Ar).
Abstract: The chiral Pt catalyst precursor Pt((R,R)-Me-Duphos)(Ph)(Cl) mediated alkylation of racemic secondary phosphines PHR(R‘) with benzyl halides in the presence of base to give enantioenriched tertiary...
TL;DR: A novel solid-phase self-organized catalyst of palladium nanoparticles was prepared from PdCl(2) with main-chain viologen polymers via complexation and reduction that efficiently promoted alpha-alkylation of ketones with primary alcohols in the presence of Ba(OH)(2)O under atmospheric conditions without organic solvents.
TL;DR: In this article, a more efficient catalytic asymmetric Friedel-Crafts alkylation of indoles with nitroalkenes using bifunctional tridentate bis(oxazoline)-Zn(OTf)(2) as catalyst has been developed.
TL;DR: A catalytic alkylation reaction was developed using an achiral ruthenium complex, which was then elaborated into a catalytic enantioselective synthesis of P-stereogenic phosphines, which can now be accessed in a single step from simple secondary phosphines and alkyl halides.
Abstract: Ruthenium phosphido complexes have been shown to be excellent nucleophiles, reacting via two-electron processes with a variety of electrophiles. A catalytic alkylation reaction was developed using an achiral ruthenium complex, which was then elaborated into a catalytic enantioselective synthesis of P-stereogenic phosphines. These useful and synthetically challenging phosphines can now be accessed in a single step from simple secondary phosphines and alkyl halides. Optimization and scope of the enantioselective alkylation are discussed.
TL;DR: New classes of nucleophiles, pyrroles, and N-methoxyamides were developed for Pd-catalyzed AAA reactions, and the feasibility of accessing (-)-agelastatin A from the same enantiomer of the chiral catalyst from the other regioisomeric piperazinone is indicated.
Abstract: New classes of nucleophiles, pyrroles, and N-methoxyamides were developed for Pd-catalyzed AAA reactions By varying the functional groups at the 2-position of pyrroles, either regioisomer of the piperazinone is available Using one regioisomer, the total synthesis of (+)-agelastatin A in 10 total steps is accomplished For this synthesis, a new copper-catalyzed aziridination and an indium-catalyzed oxidative ring opening of a N-tosylaziridine were developed The feasibility of accessing (−)-agelastatin A from the same enantiomer of the chiral catalyst from the other regioisomeric piperazinone is indicated
TL;DR: A series of group 10 bis(benzimidazolylidene) complexes featuring chelating N-(o-phenol) moieties were synthesized and characterized as discussed by the authors.
TL;DR: Crystalline Si(111) surfaces have been alkylated in a two-step chlorination/alkylation process using sterically bulky alkyl groups such as (CH3)2CH- (iso-propyl), ( CH3)3C- (tert-butyl), and C6H5- (phenyl) moieties to produce Si-H bonds on the surface.
Abstract: Crystalline Si(111) surfaces have been alkylated in a two-step chlorination/alkylation process using sterically bulky alkyl groups such as (CH3)2CH− (iso-propyl), (CH3)3C− (tert-butyl), and C6H5− (phenyl) moieties. X-ray photoelectron spectroscopic (XPS) data in the C 1s region of such surfaces exhibited a low energy emission at 283.9 binding eV, consistent with carbon bonded to Si. The C 1s XPS data indicated that the alkyls were present at lower coverages than methyl groups on CH3-terminated Si(111) surfaces. Despite the lower alkyl group coverage, no Cl was detected after alkylation. Functionalization with the bulky alkyl groups effectively inhibited the oxidation of Si(111) surfaces in air and produced low (<100 cm s-1) surface recombination velocities. Transmission infrared spectroscopy indicated that the surfaces were partially H-terminated after the functionalization reaction. Application of a reducing potential, −2.5 V vs Ag+/Ag, to Cl-terminated Si(111) electrodes in tetrahydrofuran resulted in t...
TL;DR: In this article, a 3-alkyl indole derivatives at room temperature with moderate yields and high regioselectivity using nanocrystalline titanium(IV) oxide catalyst is described.
TL;DR: The stereoselective alkylation of α, β-unsaturated imines via C−H activation followed by imine hydrolysis produces tri- and tetrasubstituted α,β-uns saturated aldehydes.
Abstract: The stereoselective alkylation of alpha,beta-unsaturated imines via C-H activation followed by imine hydrolysis produces tri- and tetrasubstituted alpha,beta-unsaturated aldehydes. In the presence of a rhodium catalyst, alpha,beta-unsaturated N-benzyl imines derived from methacrolein, crotonaldehyde, and tiglic aldehyde undergo directed C-H activation at the beta-position and react with terminal alkenes and alkynes to form the tri- and tetrasubstituted alpha,beta-unsaturated imines with very high stereoselectivity. Hydrolysis to provide alpha,beta-unsaturated aldehydes can be performed under carefully controlled conditions that maintain the stereochemistry of the beta-alkylated imine products. Alternatively, for beta-alkylation products of the N-benzyl imine of methacrolein, hydrolysis can be performed under conditions that provide complete isomerization to the E isomer.
TL;DR: A variety of zeolites, including MOR, MCM-22, SAPO-34, SOPO-11 and ZSM-5 with different SiO2/Al2O3 ratio, were used for catalyzing toluene alkylation with methanol to produce xylene.
TL;DR: Aluminumdodecatungstophosphate (AlPW12O40) is a highly water tolerant, green Lewis acid has been applied as an efficient catalyst for the preparation of indole derivatives as bis(indolyl)methanes from carbonyl compounds via Friedel-Crafts alkylation and 3-substituted indoles via Michael addition of indoles to α,β-unsaturated carbonyls compounds in CH3CN at room temperature as discussed by the authors.
Abstract: Aluminumdodecatungstophosphate (AlPW12O40) a highly water tolerant, green Lewis acid has been applied as an efficient catalyst for the preparation of indole derivatives as bis(indolyl)methanes from carbonyl compounds via Friedel–Crafts alkylation and 3-substituted indoles via Michael addition of indole to α,β-unsaturated carbonyl compounds in CH3CN at room temperature
TL;DR: Gold chloride and BF 3. etherate were tested as Friedel-Crafts catalysts in the propargylation of electron-rich arenes as mentioned in this paper, showing that gold catalysts exhibited a pronounced selectivity, whereas p-toluenesulfonic acid as catalyst opened up a competing pathway to a structural isomer.
Abstract: Gold chloride and BF 3 . etherate were tested as Friedel-Crafts catalysts in the propargylation of electron-rich arenes: differences in reactivity of the catalysts can be used to achieve high selectivity either for monoalkylation or for multiple alkylation products. In the case of a macrocyclization towards a heterocalixarene, gold catalysts exhibited a pronounced selectivity, whereas p-toluenesulfonic acid as catalyst opened up a competing pathway to a structural isomer.
TL;DR: It is demonstrated that Fe(III) salts are effective precatalysts for the carbometalation of alkynes through an unusual addition/cyclization reaction to generate cyclic dienes.
Abstract: Nucleophilic addition to alkynes represents an attractive approach to the synthesis of olefins. Obstacles to this strategy include the low reactivity of alkynes toward many organometallic reagents and difficulties associated with controlling the regioselectivity of addition. Here we demonstrate that Fe(III) salts are effective precatalysts for the carbometalation of alkynes. Primary and secondary propargylic and homopropargylic alcohols react with alkyl and aryl Grignard reagents to provide Z-allylic and -homoallylic alcohols as single stereo and regioisomers. Alkylation and arylation occur distal to the alcohol. Common oxygen protecting groups and tertiary nitrogens are tolerated. The intermediate vinyl magnesium or iron species can be trapped with a variety of electrophiles including aldehydes, allyl bromide, and N-bromosuccinimide. Diyne substrates undergo an unusual addition/cyclization reaction to generate cyclic dienes. A brief discussion of mechanism is included.
TL;DR: A ruthenium complex of Xantphos has been shown to be a good catalyst for the alkylation of active methylene compounds with a range of alcohols.