Markovnikov Addition Research Articles

Selective Ruthenium‐Catalyzed Hydrochlorination of Alkynes: One‐Step Synthesis of Vinylchlorides

An unprecedented ruthenium-catalyzed direct and selective alkyne hydrochlorination is reported and leads to vinylchlorides in excellent yields with atom economy. The reaction proceeds at room temperature from terminal alkynes and provides a variety of chloroalkenes. Only the regioisomer resulting from the formal Markovnikov addition is selectively formed. Mechanistic studies show the stereoselective syn addition of HCl to alkynes at room temperature and suggest a chloro hydrido Ru(IV) species as a key intermediate of the reaction.

ChemInform Abstract: Hydroxyamination of Olefins Using Br—N—(CO2Me)2.

The hydroxyamination reagent Br-N-(CO2Me)2 underwent Markovnikov addition to various olefins in the presence of catalytic BF3·OEt2 and provides efficient access to aminoalcohols. The reaction provided the trans-1-bromo, 2-N-bis-carbamate adduct stereoisomer in all cases. The resulting adduct underwent cyclization to give an oxazolidinone, which could be readily hydrolyzed to an oxazolidin-2-one or an amino alcohol.

ChemInform Abstract: Early Steps of Homogeneous Catalysis in Rennes: Carbon Dioxide Incorporation, Alkyne Activation and Ruthenium Catalysis

AbstractReview: 109 refs.

Role of ligands in controlling the regioselectivity in ruthenium-catalysed addition of carboxylic acids to terminal alkynes: A DFT study

Density functional studies are performed to understand the role of chelating bi-phosphine ligands [(Ph 2P(CH 2) m PPh 2); m = 1–4] in modulating the regio-selectivity of benzoic acid addition to 1-hexyne, in presence of ruthenium(II) catalyst [(Ph 2P(CH 2)mPPh 2)Ru(methallyl) 2]. The Markovnikov addition to 1-hexyne is observed when catalyst 1 a [(Ph 2P(CH 2)PPh 2)Ru(methallyl) 2] is employed, whereas a reverse regio-selectivity is witnessed in presence of 1 d [(Ph 2P(CH 2)4PPh 2)Ru(methallyl) 2]. Anti-Markovnikov addition occurs via the neutral vinylidene intermediates (5 a / d ) formed after 1,2-hydrogen shift in hexyne coordinated ruthenium(II) complexes 3 a / d . The energy profile shows clear preference for Markovnikov addition by 15.0 kcal/mol (\({\Delta } G_{\mathrm {L}}^{S})\) in case of catalyst system 1 a . In contrast, anti-Markovnikov pathway following neutral vinylidenes are more favourable by 9.1 kcal/mol (\({\Delta } G_{\mathrm {L}}^{S})\) for catalyst system 1 d . The Z-enol ester formation is more predominant in the anti-Markovnikov pathway since the activation barrier for this step requires less energy (5.9 kcal/mol, \({\Delta } G_{\mathrm {L}}^{S})\) than the one furnishing the E-product. The calculated results are in good agreement with the reported experimental findings. Preliminary DFT studies are performed to explore the mechanistic pathway of the benzoic acid addition to 1-hexyne in presence of Ru(II) catalyst. Our calculations emphasized on the understanding of the regio-selectivity controlled by the chelating bi-phosphine ligand present in catalysts. Markovnikov product formation is the lower energy pathway in case of least spacer group (CH2) whereas it is anti-Markovnikov product for the highest spacer group, {(CH2)4} in bi-phosphine ligands.

Hydroxyamination of olefins using Br-N-(CO2Me)2.

The hydroxyamination reagent Br-N-(CO2Me)2 underwent Markovnikov addition to various olefins in the presence of catalytic BF3·OEt2 and provides efficient access to aminoalcohols. The reaction provided the trans-1-bromo, 2-N-bis-carbamate adduct stereoisomer in all cases. The resulting adduct underwent cyclization to give an oxazolidinone, which could be readily hydrolyzed to an oxazolidin-2-one or an amino alcohol.

Rhenium-catalyzed anti-Markovnikov addition reaction of methanetricarboxylates to unactivated terminal acetylenes.

A novel anti-Markovnikov addition reaction of methanetricarboxylates with terminal acetylenes under neutral conditions was achieved using a rhenium complex. This transformation represents a rare example of intermolecular anti-Markovnikov addition of carbon nucleophiles to unactivated terminal acetylenes. 1,3-Diesters having bulky substituents at the active methylene carbon are also applicable as substrates to provide anti-Markovnikov adducts as single regio- and stereoisomers. Preliminary mechanistic studies imply that the rhenium vinylidene species is the key intermediate in the current catalytic cycle.

Synthesis of Dithiocarbamates by Markovnikov Addition Reaction in PEG and Their Application in Amidoalkylation of Naphthols and Indoles

Synthesis of dithiocarbamates by the one-pot three-component Markovnikov addition reaction of an amine, carbon disulfide and an alkyl vinyl ether or N-vinylpyrrolidone is reported in polyethylene glycol (PEG) under a mild and green procedure with high yields and completely regiospecific. Also, the products were used as efficient starting materials for amidoalkylation of electron-rich arenes such as naphthols and indoles.

Rapid Markovnikov addition of HCl to a pendant alkyne: evidence for a quinoidal cumulene

Reaction of cis-[RuCl2(dppm)2]BF4 with TlBF4 and 1,4-diethynyl-benzenes results in the formation of the vinylidene cations trans-[Ru([double bond, length as m-dash]C[double bond, length as m-dash]CH-C6H2-2,5-R2-4-C[triple bond, length as m-dash]CH)Cl(dppm)2](+) (R = H, Me). Subsequent reaction with [N(n)Bu4]Cl results in nucleophilic attack at the coordinated organic ligand, but not at the expected metal-bound carbon atom. Instead, trans-[Ru(C[triple bond, length as m-dash]C-C6H2-2,5-R2-4-CCl[double bond, length as m-dash]CH2)Cl(dppm)2] was generated which, when coupled with DFT calculations, provides evidence for an intermediate quinoidal cumulene complex.

Early Steps of Homogeneous Catalysis in Rennes: Carbon Dioxide Incorporation, Alkyne Activation and Ruthenium Catalysis

This review reports the first discoveries in homogeneous catalysis in Rennes. Ruthenium(II) catalysts are shown to promote the activation of terminal alkynes and the synthesis of vinylcarbamates on addition of CO2 and amines. The ruthenium–vinylidene are the key catalytic species. Applications to the addition of carboxylic acids to alkynes have opened the access to various enolesters and dienylesters via controlled catalyzed Markovnikov or anti-Markonikov additions. The catalytic synthesis of α-methylene cyclic carbonates and oxazolidinones from propargylic alcohols and CO2 is presented and shown to lead to allene derivatives via palladium catalysis. Cp*RuX(COD) catalyst promote the head to tail oxidative couplings of alkene with alkyne, and the synthesis of functional dienes via 1,4 addition of H-nucleophiles to the biscarbene-ruthenium intermediate arising from head to head couplings of alkynes, whereas Cp*RuL2 + catalysts favour activation of alkynes via vinylidene intermediate. This historical review presents the first steps in homogeneous catalysis in Rennes starting in 1985 with ruthenium(II) catalysts promoting the activation of terminal alkynes via ruthenium–vinylidene or oxidative couplings for the synthesis of CO2 derivatives: vinylcarbamates, carbonates or oxazolidinones, enolesters and functional dienes.

ChemInform Abstract: Gold‐Catalyzed Intermolecular C—S Bond Formation: Efficient Synthesis of α‐Substituted Vinyl Sulfones.

AbstractThe first gold‐catalyzed Markovnikov addition of sulfinic acids to terminal alkynes is presented.

Ruthenium(II) bipyridine complexes bearing new keto–enol azoimine ligands: Synthesis, structure, electrochemistry and DFT calculations

The novel azoimine ligand, PhNHNC(COCH3)NHPh(CCH) (H2L), was synthesized and its molecular structure was determined by X-ray crystallography. Catalytic hydration of the terminal acetylene of H2L in the presence of RuCl3·3H2O in ethanol at reflux temperature yielded a ketone (L1=PhNNC(COCH3)NPh(COCH3) and an enol (L2=PhNNC(COCH3)NPhC(OH)CH2) by Markovnikov addition of water. Two mixed-ligand ruthenium complexes having general formula, trans-[Ru(bpy)(Y)Cl2] (1–2) (where Y=L1 (1) and Y=L2 (2), bpy is 2.2′-bipyrdine) were achieved by the stepwise addition of equimolar amounts of (H2L) and bpy ligands to RuCl3·3H2O in absolute ethanol. Theses complexes were characterized by elemental analyses and spectroscopic (IR, UV–Vis, and NMR (1D 1H NMR, 13C NMR, (DEPT-135), (DEPT-90), 2D 1H–1H and 13C–1H correlation (HMQC) spectroscopy)). The two complexes exhibit a quasi-reversible one electron Ru(II)/Ru(III) oxidation couple at 604mV vs. ferrocene/ferrocenium (Cp2Fe0/+) couple along with one electron ligand reduction at −1010mV. The crystal structure of complex 1 showed that the bidentate ligand L1 coordinates to Ru(II) by the azo- and imine-nitrogen donor atoms. The complex adopts a distorted trans octahedral coordination geometry of chloride ligands. The electronic spectra of 1 and 1+ in dichloromethane have been modeled by time-dependent density functional theory (TD-DFT).

ChemInform Abstract: Tandem Regio‐ and Diastereo‐Selective Synthesis of Halogenated C‐Vinyl Glycosides from Unactivated Arylacetylenes.

A highly regio- and diastereo-selective synthesis of halogenated C-vinyl glycosides has been achieved from glycals and unactivated aryl acetylenes in the presence of halogenated Lewis acids via a tandem glycosylation–halogenation reaction. The Lewis acid used served the dual purpose of activating the allylic acetoxy group of glycals and serving as halogen source for Markovnikov addition across the triple bond, which makes the process atom economic. The synthesized glycosyl vinyl halides have been used as precursors for various Pd catalyzed C–C cross coupling reactions.

Prins cyclization of α-bromoethers under basic conditions

α-Bromoethers have been found to undergo Prins-type cyclization under basic conditions and without the need to add a promoter. The products are those derived from a Markovnikov addition on the pendant alkene. However, the stereochemistry and even the structure of the products sometimes differ from those expected with the classical Lewis-acid-catalyzed Prins reaction of acetals.

ChemInform Abstract: Three‐Component Reaction Between Secondary Phosphine Sulfides, Elemental Selenium and Vinyl Ethers: The First Examples of Markovnikov Addition of Thioselenophosphinic Acids to Double Bond.

Abstract Thioselenophosphinic acids, R2P(Se)SH, generated in situ from secondary phosphine sulfides and elemental selenium, easily add to various vinyl ethers (equimolar ratio, 100 °C, 1,4-dioxane, up to 40 min) to give earlier unknown S- and Se-[1-(organyloxy)ethyl]thioselenophosphinates, i.e., R2P(Se)SCH(Me)OR′ and R2P(S)SeCH(Me)OR′ (R, R′=alkyl, aralkyl, hetaralkyl and aryl), the S-esters being predominant (73–95% total yield).

MARKOVNIKOV ADDITION OF CHLOROSULFURIC ACID TO EUGENOL ISOLATED FROM CLOVE OIL

The objective of this research was to synthesize new compounds with potential biological activity from readily accessed natural products. Eugenol has been reported to posses antioxidant and anticancer properties and was prepared by extracting from clove buds with dichloromethane and followed by isolation using column chromatography to afford pure eugenol (73%). In an attempt to enhance intrinsic activity of this natural compound, some derivatives were possible to synthesize. The main aim of this preliminary research was to transform eugenol to become sulfonic derivative. Eugenol was transformed to its sulfonic derivative in moderate yield (64%) by treatment with chlorosulfuric acid which undergoes Markovnikov addition. This product was rapidly confirmed by GC-MS and NMR analyses. Selective inhibition was performed by cyclic sulfonic ester derivative which could inhibit Eschericia coli and Staphylococcus aureus but not for Bacillus cereus.

Three-component reaction between secondary phosphine sulfides, elemental selenium and vinyl ethers: the first examples of Markovnikov addition of thioselenophosphinic acids to double bond

Thioselenophosphinic acids, R2P(Se)SH, generated in situ from secondary phosphine sulfides and elemental selenium, easily add to various vinyl ethers (equimolar ratio, 100 °C, 1,4-dioxane, up to 40 min) to give earlier unknown S- and Se-[1-(organyloxy)ethyl]thioselenophosphinates, i.e., R2P(Se)SCH(Me)OR′ and R2P(S)SeCH(Me)OR′ (R, R′=alkyl, aralkyl, hetaralkyl and aryl), the S-esters being predominant (73–95% total yield).

DESIGN AND SYNTHESIS OF POLYPROPYLENE b POLYPHOSPHATE BLOCK COPOLYMERS

Novel phosphorus-containing polypropylene diblock copolymers were synthesized and their thermal decomposing behaviors and flammability were characterized by thermo-gravimetric analysis(TGA) and micro-scale combustion calorimetry(MCC).First,a reactive polypropylene precursor with a terminal styryl group(PP-t-St) at polymer chain end was synthesized via controlled chain transfer reaction to 1,4-divinylbenzene and hydrogen in metallocene-mediated propylene polymerization.Then PP-t-St was reacted with hydrogen bromide through Markovnikov addition in a quasi-quantitative manner,affording 1-bromoethylbenzene group-terminated polypropylene(PP-t-BzBr).ATRP of phosphorous-containing vinyl monomer such as diethyl-(4-vinylbenzyl)phosphonate(DEVBP) was carried out in toluene at elevated temperatures with PP-t-BzBr suspending in the reactant solution,with CuCl/1,1,4,7,10,10-hexamethyltriethylenetetramine(HMTETA) as catalyst.Diblock copolymers containing different amounts of DEVBP units(up to 64.3 wt%) were obtained by adjusting polymerization durations.Differential scanning calorimetry(DSC) experiments indicated that both the crystallinity and crystallization rate of PP were largely retained in PP-b-PDEVBP diblock copolymers.TGA and MCC results showed that char residues increased while heat release rates reduced upon forming the diblock copolymers as compared to the precursory PP-t-BzBr as well as PP-t-St.Overall,this research may lead to a new solution to inherently flame-retardant polypropylene.

ChemInform Abstract: AgOTf Catalyzed Hydration of Terminal Alkynes.

AbstractThis is the first report of gold‐free silver catalysis for hydration of terminal alkynes to the Markovnikov addition product.

Ubiquitous Alkyne Activity

Chemistry Over the past decade, the coupling of terminal alkynes with azides—so efficient it's been termed a “click” reaction—has become a prevalent means of linking together larger molecular fragments. One advantage of the scheme was that the alkynes appeared to be otherwise inert in cellular environments, thereby enabling high specificity in the design of various biochemical probes. Two studies now report that terminal alkynes do in fact react with certain enzymes. Ekkebus et al. show that appending the alkyne to the C terminus of ubiquitin leads to inhibition of deubiquitinating enzymes. Crystallography revealed covalent linkage to an active site cysteine, the product of formal Markovnikov addition of the thiol group across the carbon-carbon triple bond (though no reaction was observed with free thiol). Sommer et al. observed the same reaction of C-terminally propargylated small ubiquitin-like modifier (SUMO) with its protease. Scavenger experiments in both studies disfavor a radical mechanism. Both studies leveraged the observation for selective labeling of lysates and suggest that this reaction could have broad application in selective inhibition. J. Am. Chem. Soc. 135 , 2867; Bioorg. Med. Chem. 21 , 10.1016/j.bmc.2013.02.039 (2013).

Potassium carbonate as a green catalyst for Markovnikov addition of azoles to vinyl acetate in PEG

A novel strategy to effect the Markovnikov addition between azoles and vinyl-acetate is described. The main attractive features of this process are a mild base catalyst, recyclability of solvent PEG, excellent yields of products, and easy workup procedure.