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• 768-70-7 1-ethynyl-3-methoxybenzene 
• 7621-89-8 3-(3-methoxyphenyl)propiolic acid 

Relevant academic research and scientific papers

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.

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 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.

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.

CuSO4-H-phosphonate catalyzed highly stereo- and regioselective dimerization of terminal alkynes

The readily available CuSO4-H-phosphonate catalytic system can catalyze the head-to-head dimerization of terminal alkynes to give the corresponding (E) conjugated enynes selectively in high yield. The present protocol provides an efficient and

Microwave-assisted palladium-catalyzed highly regio- and stereoselective head to head dimerization of terminal aryl alkynes in water

A highly regio- and stereoselective oxime palladacycle/imidazolinium-catalyzed head to head dimerization of terminal aryl alkynes in water is presented. The reaction, which is carried out at 130 °C under microwave irradiation in the presence of 1,3-bis-(2,6-diisopropylphenyl)imidazolinium chloride as ligand, triethylamine as base, and TBAB as surfactant, allows the synthesis of (E)-1,4-enynes as single stereoisomers in good isolated yields.

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.

Hydrido-cobalt catalyst as a selective tool for the dimerisation of arylacetylenes: Scope and theoretical studies

A simple hydrido-cobalt complex efficiently catalyses the highly regio- and stereoselective dimerisation of various terminal arylacetylenes under mild conditions. The corresponding (E)-1,4-enynes are obtained as sole isomers with good to excellent yields. DFT calculations revealed that the reaction proceeds via a C-H activation/hydrocobaltation pathway. Copyright

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.