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• 767-91-9 1-ethynyl-2-methoxybenzene 
• 7342-00-9 3-(2-methoxyphenyl)prop-2-ynoic acid 

Relevant academic research and scientific papers

Ligand-Controlled Diastereoselective Cobalt-Catalysed Hydroalkynylation of Terminal Alkynes to E- or Z-1,3-Enynes

A diastereoselective hydroalkynylation of terminal alkynes to form the head-to-head dimerization products by two different cobalt-phosphine catalyst system is reported. The use of the bidentate ligand dppp and additional triphenylphosphine led to the selective formation of the (E)-1,3-enynes (E:Z>99:1) in good to excellent yields, while the tridentate ligand TriPhos led to the corresponding (Z)-1,3-enynes in moderate to good yields with excellent stereoselectivities (up to E:Z=1:99). Both pre-catalysts are easy to handle, because of their stability under atmospheric conditions. The optimized reaction conditions were identified by the Design of Experiments (DoE) approach, which has not been used before in cobalt-catalysed reaction optimisation. DoE decreased the number of required reactions to a minimum.

A practical ruthenium based catalytic system bearing a switchable selectivity between the dimerization and cyclotrimerization reactions of alkynes

In this study, a practical and inexpensive switchable catalytic system (cyclotrimerization vs. dimerization), [RuCl2(p-cymene)] 2/PR3 has been developed for the catalytic dimerization of terminal alkynes. Bulky and basic phosphine derivatives, PCy3 and P(i-Pr)3, were used with [RuCl2(p-cymene)] 2 and excess of terminal alkyne to in situ formation of vinylidenic intermediates which are active towards dimerization reactions. Effect of phosphine/ruthenium ratio has been investigated. A solvent study was carried out and toluene was found to be the most versatile solvent for both cyclotrimerization and dimerization reactions. A set of aryl and alkyl acetylenes were chosen as substrates to investigate the effect of the nature of the substrates on alkyne dimerization reactions catalyzed by [RuCl 2(p-cymene)]2/PR3. In conclusion, we have shown that [RuCl2(p-cymene)]2/PCy3 can be used as a practical and inexpensive catalytic system which has a switchable selectivity towards cyclotrimerization and dimerization reactions. Best results in means of regioselectivity and yield were observed by using arylacetylene derivatives in these reactions. This catalytic system emerges as an economical method for the transformation of arylacetylenes to corresponding enyne and arene derivatives in excellent yields and selectivity.

A K-arylacetylide complex for catalytic terminal alkyne functionalization using KO: TBu as a precatalyst

Herein we report a transition metal free catalytic terminal alkyne functionalization across the C-X triple bond (X = CH and N) with E-selective homo (alkyne-alkyne) and head-to-tail selective hetero (alkyne-nitrile) dimerization. A series of stoichiometric reactions enabled us to crystallize a reactive organometallic intermediate K-arylacetylide complex which was characterized by X-ray crystallography, indicating that an ionic mechanism is operative.

Stereo- A nd regioselective dimerization of alkynes to enynes by bimetallic syn-carbopalladation

Enynes are important motifs in bioactive compounds. They can be synthesized by alkynea'alkyne couplings for which a number of mechanisms have been suggested depending on catalyst type and dominant product isomers. Regarding bimetallic pathways, hydrometalations and anti-carbopalladations have been discussed to account for the formation of geminally substituted and (Z)-configured enynes, respectively. Here we report a bimetallic alkynea'alkyne coupling that yields (E)-configured enynes. An unusual type of acetylide Pd bridging was found in putative catalytic intermediates which is arguably responsible for the regio- A nd stereochemical reaction outcome. Mechanistic studies suggest that a double μa'κ:η2 acetylide bridging enables a bimetallic syn-carbometalation. Interestingly, depending on the reaction conditions, it is also possible to form the geminal regioisomer as major product with the same catalyst. This regiodivergent outcome is explained by bi-versus monometallic reaction pathways.

Palladium-Catalyzed Decarboxylative Homodimerization of Propiolic Acids: Synthesis of 1,3-Enynes

The 1,3-enyne product was obtained as a result of a decarboxylative homodimerization reaction when a variety aryl propiolic acids were reacted in the presence of Pd(TFA)2/i-PrPPh2 and K2CO3. It was found that aryl propiolic acids bearing an electrondonating substituent provided the desired product; however, aryl propiolic acids an bearing electron-withdrawing substituent did not give the desired product.

Cyclic (Alkyl)amino Carbene Based Iron Catalyst for Regioselective Dimerization of Terminal Arylalkynes

[(cAAC)Fe(CO)4] (1) catalyzed head-to-head dimerization of terminal arylalkynes toward conjugated enynes in very high yield and high E selectivity (up to 84:16 E:Z). The protocol can be performed under extremely low catalyst loading down to 0.01 mol %, resulting in a high TON of 6500. A mechanistic pathway for arylalkyne dimerization has been proposed on the basis of a well-defined catalyst, an isolable intermediate, and quantum chemical calculations.

Ligand mediated iron catalyzed dimerization of terminal aryl alkynes: Scope and limitations

Regioselective dimerization of terminal aryl alkynes to produce conjugated enynes has been achieved using FeCl3 and KOtBu in the presence of either DMEDA or dppe. The reaction proceeds smoothly in toluene at 145°C for 2 h to give the corresponding head-to-head dimers in good to excellent yields (54 to 99%) with high E-selectivity (67:33 to 83:17 E/Z). Both strongly electron-donating and electron-withdrawing groups are compatible with this procedure. The bidentate phosphine (dppe) ligand exhibits better catalytic activity than the bidentate amine (DMEDA). The aliphatic acetylene fails to react under this catalytic system which suggests that potassium tertiary butoxide activates the conjugated system of aryl acetylene through cation-pi interaction and pi-pi interaction. A radical inhibitor (galvinoxyl or TEMPO) completely suppresses the reaction. Employing FeCl2 as a catalyst instead of FeCl3, only phenyl acetylene afforded the corresponding head to head dimer in good yield. Mechanistic pathways for both FeCl3 catalyzed dimerization of aryl alkynes and FeCl2 catalyzed dimerization of phenyl acetylene have been proposed.

A ruthenium-based catalytic system with switchable selectivity between cyclotrimerization and enyne metathesis/Diels-Alder reactions of terminal alkynes

In this study, we report a practical catalytic system, [RuCl 2(p-cymene)]2/IPr (IPr: 1,3-bis(2,6 diisopropylphenyl) imidazol-2-ylidene), that can switch between cyclotrimerization and cross enyne metathesis. The cyclotrimerization reaction of phenylacetylene catalyzed by [RuCl2(p-cymene)]2 can be switched to enyne metathesis by the introduction of a sterically hindered N-heterocyclic carbene. The 1,3-diene formed during this reaction reacts with dienophiles to form the Diels-Alder adduct. A practical one-pot synthesis method, utilizing enyne metathesis/Diels-Alder reactions, was used to construct cyclic compounds in an efficient manner.

Dimerization of terminal arylalkynes in aqueous medium by ruthenium and acid promoted (RAP) catalysis: Acetate-assisted (sp)C-(sp2)C bond formation

The hexamethylbenzene ruthenium(II) dimer [{RuCl(m-Cl)(h6-C 6Me6)}]2 (5 mol%), tested among a series of ruthenium(II) and ruthenium(IV) complexes, represents an efficient precatalyst source for the dimerization of terminal arylalkynes ArCΞ CH [Ar=C 6H5, 3,4,5-(OMe)3C6H2, 4-MeOC 6H6, 2-MeOC6H6, 4-MeC 6H6, 2,4,5-Me3C6H2, 4-BrC 6H6, 4-ClC6H6, 4-FC 6H6, 4-HC(=O)C6H6, 4-CH 2=CHC6H6, 3-NCC6H6, 4-O2NC6H6, 4-EtO2C-(CH2)3OC6H 6, 4-HO(CH2CH2O)3C6H 6, 3-HO(CH2CH2O)3-C 6H6] in acetic acid/water mixture (1:1, v/v). The reactions proceed for 24 h at room temperature under heterogeneous conditions and afford the dimeric enyne derivatives (E)-Ar-CH=CH-C-C-Ar in high yields and stereoselectivity. The preformed acetato complex [RuCl(h6-C 6Me6)(k2-OAc)] catalyzes the dimerization of phenylacetylene under analogous conditions, with rapid substrate conversion. The presence of cosolvents of acetic acid different from water reduces dramatically the efficiency and selectivity of the reaction. The aqueous medium facilitates the activation stage of the precatalyst by assisting the splitting of the ruthenium dimer. The addition or generation in situ of acetate salts results in shorter reactions times (0.5-3 h) and excellent yields, due to the rapid formation of active acetato complexes. Circumstantial evidence indicates that the p-bound alkyne molecule is activated by intramolecular proton abstraction. This is currently the most efficient, E-selective and wide-scope catalytic system for the alkyne dimerization reaction in protic aqueous media.

Iron catalyzed highly regioselective dimerization of terminal aryl alkynes

Iron can catalyze head-to-head dimerization of terminal aryl alkynes to give the corresponding (E) selective conjugated enynes in high yields. A variety of substituted aryl acetylenes underwent smooth dimerization using catalytic FeCl3 and DMEDA in the presence of KOtBu.