Silver-Mediated anti-Markovnikovand Markovnikov-Selective Hydrotrifluoromethylthiolationof Terminal Alkynes
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Markovnikov's rule
Abstract Palladium acetate efficiently catalyzes the addition of an H-spirophosphorane (pinacolato)2PH to alkynes to give Markovnikov addition products highly selectively. The addition products can be easily converted to the corresponding alkenylphosphonates and phosphonic acids via simple hydrolysis or thermal decomposition. This new reaction is a general method for the introduction of phosphorus functionality to the internal carbons of terminal alkynes, resolving the problem of the regioselectivity associated with hydrophosphorylation reactions so far reported. Mechanistic studies confirmed that (a) palladium acetate was reduced to metallic palladium by H-spirophosphorane, (b) the P–H bond of H-spirophosphorane could be activated by zero-valent platinum complexes to give the corresponding hydridoplatinum complexes, and (c) an alkenylpalladium species was identified from the reaction of palladium acetate with H-spirophosphorane and diphenylacetylene. These results support a reaction mechanism that palladium acetate was first reduced by H-spirophosphorane to give zero-valent palladium. This zero-valent palladium might insert into the P–H bond of the H-spirophosphorane to give a hydridopalladium species which then added to alkyne via the addition of H–Pd bond to form an alkenylpalladium species with the hydrogen atom added to the terminal carbon of alkynes. Reductive elimination of the alkenylpalladium affords the addition product.
Markovnikov's rule
Alkyne
Reductive elimination
Hypervalent molecule
Diphenylacetylene
Triple bond
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Against the grain: The anti-Markovnikov addition of hydrazines to terminal alkynes in the presence of [TpRh(C2H4)2]/P(2-furyl)3 (Tp=trispyrazolylborate) as a catalyst system has been developed. N-alkyl- and N,N-dialkyl-substituted hydrazines are applicable to this highly regioselective hydrohydrazination, which affords aldimine-type hydrazine derivatives.
Markovnikov's rule
Aldimine
Hydrazine (antidepressant)
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Abstract S‐(Trifluoromethyl)diarylsulfonium triflate is described as reagent for the Cu‐mediated reaction with terminal alkynes to give trifluoromethylated alkynes (III) generally in good yields,
Trifluoromethylation
Trifluoromethanesulfonate
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We have developed a method for stereospecific synthesis of E-alkenes from terminal alkynes and alkyl iodides. The hydroalkylation reaction is enabled by a cooperative action of copper and nickel catalysts and proceeds with excellent anti-Markovnikov selectivity. We demonstrate the broad scope of the reaction, which can be accomplished in the presence of esters, nitriles, aryl bromides, ethers, alkyl chlorides, anilines, and a wide range of nitrogen-containing heteroaromatic compounds. Mechanistic studies provide evidence that the copper catalyst activates the alkyne by hydrocupration, which controls both the regio- and diastereoselectivity of the overall reaction. The nickel catalyst activates the alkyl iodide and promotes cross coupling with the alkenyl copper intermediate.
Markovnikov's rule
Stereospecificity
Alkyne
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The anti-Markovnikov hydration of terminal alkynes to give aldehydes is catalyzed by complexes derived in situ from air-stable [CpRu(η6-naphthalene)]PF6 (C) and 6-aryl-2-diphenylphosphinopyridines (L). Ligands L are readily available from a modular synthesis. Increasing the size of the ligand C-6 aryl group in the order R = Ph < mesityl < 2,4,6-triisopropylphenyl < (2,4,6-triphenyl)phenyl gave hydration catalysts of highest known activity.
Markovnikov's rule
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The first catalytic addition of terminal alkynes to simple cyclic ketones in water catalyzed by silver was developed. Cyclic ketones were reacted with terminal alkynes efficiently in water to give the corresponding propargyl alcohols.
Propargyl
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Anti-Markovnikov hydroamination of both aliphatic and aromatic terminal alkynes with primary amines was achieved using an 8-quinolinolato rhodium catalyst to form aldimines and enamines in high yields. This catalytic system realized high functional group tolerance including hydroxy, bromo, cyano, and thioester groups.
Hydroamination
Markovnikov's rule
Aldimine
Thioester
Primary (astronomy)
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Terminal alkynes react with secondary amines in the presence of TpRh(C2H4)2/PPh3 (Tp = trispyrazolylborate) to give anti-Markovnikov E-enamines. Both Tp and PPh3 ligands are essential for the reaction. The reaction tolerates functional groups, such as ester, nitrile, and siloxy groups, on the terminal alkynes. Primary amines also add to terminal alkynes in anti-Markovnikov fashion, yielding the corresponding imines. The formation of a vinylidene−rhodium complex followed by the intermolecular nucleophilic attack by an amine nitrogen at the α-carbon atom of the vinylidene−metal intermediate may be involved in a key step in the catalytic reaction.
Markovnikov's rule
Primary (astronomy)
Alkyne
Nucleophilic Addition
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Abstract ChemInform 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.
Markovnikov's rule
Aqueous medium
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The first example of the metal- and solvent-free B(C6F5)3-catalyzed Markovnikov addition of indoles to aryl alkynes was disclosed. Both N-H and N-protected indoles were tolerated, leading to a wide spectrum of versatile bis(indolyl)alkanes in moderate to good yields with high regioselectivities.
Markovnikov's rule
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