Chemoselective Cobalt(I)-Catalyzed Cyclotrimerization of (Un)Symmetrical 1,3-Butadiynes for the Synthesis of 1,2,4-Regioisomers

Weber, Sebastian M.; Hilt, Gerhard

doi:10.1021/acs.orglett.9b01281

Cited by 17 publications

(9 citation statements)

References 39 publications

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“…Our group developed a catalyst system consisting of CoBr 2 (dppp), triphenylphosphine, and zinc as reducing agent in acetonitrile. In comparison to our previous reported catalyst systems concerning cyclotrimerization reactions (Hilt et al, 2005b;Weber and Hilt, 2019), the addition of triphenylphosphine and the absence of the Lewis acid led to a complete change in the selectivity toward the head-to-head dimer 2 (Scheme 16) (Weber et al, 2020).…”

Section: E-selective Head-to-head Dimerizationcontrasting

confidence: 53%

Late 3d Metal-Catalyzed (Cross-) Dimerization of Terminal and Internal Alkynes

Weber

Hilt

2021

Front. Chem.

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This review will outline the recent advances in chemo-, regio-, and stereoselective (cross-) dimerization of terminal alkynes to generate 1,3-enynes using different types of iron and cobalt catalysts with altering oxidation states of the active species. In general, the used ligands have a crucial effect on the stereoselectivity of the reaction; e.g., bidentate phosphine ligands in cobalt catalysts can generate the E-configured head-to-head dimerization product, while tridentate phosphine ligands can generate either the Z-configured head-to-head dimerization product or the branched head-to-tail isomer. Furthermore, the hydroalkynylation of silyl-substituted acetylenes as donors to internal alkynes as acceptors will be discussed using cobalt and nickel catalysts.

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Section: E-selective Head-to-head Dimerizationcontrasting

confidence: 53%

Late 3d Metal-Catalyzed (Cross-) Dimerization of Terminal and Internal Alkynes

Weber

Hilt

2021

Front. Chem.

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“…The alkynyl arenes with substituents in meta ‐position gave yields around 48 %. Normally, ortho ‐substituted alkynyl arenes with donor‐substituents in ortho ‐position cause more problems, due to their steric demand near to the catalyst . Interestingly, the products 2 n and 2 o gave considerably better yields between 70–72 % compared to those with the same substituents in meta ‐position ( 2 l / 2 m ).…”

Section: Methodsmentioning

confidence: 99%

“…The alkynyla renes with substituents in meta-position gave yields around4 8%.N ormally, ortho-substituted alkynyl arenes with donor-substituents in ortho-position cause more problems, due to their steric demand near to the catalyst. [4,17] Interestingly, the products 2n and 2o gave considerably better yields between 70-72 %c ompared to those with the same substituents in meta-position (2l/2m). Also, pyridinyl substituted alkynesw ere tolerated and gave the desired products 2p/q in good yields, as well as the ethynylt hiophened erivative which gave the products 2r in am oderate yield.…”

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confidence: 95%

“…The transition-metal-catalysed Markovnikov-type addition (head-to-tail) leads to the conjugated enyne 1 whereas the anti-Markovnikov additiong enerates either the E-ort he Z-configured enynes 2 and 3 (head-to-head products).F or the selective formation of only one of these products the catalyst must control the regio-a nd the stereochemistry of this transformation. [2] Also, the catalyst must allow the coordination of two alkynes to the transition metal but not the incorporationo fa third alkyne which wouldl ead to the well-known cyclotrimerization [3,4] towards areneso ra nu ndesired polymerization towards polyacetylenes. In the past, excellent results for the dimerizationo ft erminal alkynes were obtained when precious metalc atalysts, for example, Pd, were applied to realize the hydroalkynylation products of type 1 in good to excellent yields.…”

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confidence: 99%

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

Weber

Queder

Hilt

2020

Chemistry A European J

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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.

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“…The reaction was achieved in the presence of 5 mol% CoBr 2 (dppe) with 10 mol% Zn and 10 mol% ZnI 2 in THF at 60 °C for 18 h (Scheme 15). 75 With respect to unsymmetrical buta-1,3-diynes, a single 1,2,4-substituted isomer was obtained in 15-97% yield and >99:1 regioselectivities (not shown). Nevertheless, a steric effect of the alkyne residue was observed toward the chemo-and regioselectivity of the cycloisomerization (R 2 = 4-FC 6 H 4 , R 1 = t-Bu, >99:1 rr, R 1 = Et, i-Pr, 7 detectable isomers).…”

Section: Review Synthesis Scheme 14mentioning

confidence: 97%

Recent Progress in Metal-Catalyzed [2+2+2] Cycloaddition Reactions

Matton¹,

Huvelle²,

Haddad³

et al. 2021

Synthesis

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Metal-catalyzed [2+2+2] cycloaddition is a powerful tool that allows rapid construction of functionalized 6-membered carbo- and heterocycles in a single step through an atom-economical process with high functional group tolerance. The reaction is usually regio- and chemoselective although selectivity issues can still be challenging for intermolecular reactions involving the cross-[2+2+2] cycloaddition of two or three different alkynes and various strategies have been developed to attain high selectivities. Furthermore, enantioselective [2+2+2] cycloaddition is an efficient means to create central, axial, and planar chirality and a variety of chiral organometallic complexes can be used for asymmetric transition-metal-catalyzed inter- and intramolecular reactions. This review summarizes the recent advances in the field of [2+2+2] cycloaddition.1 Introduction2 Formation of Carbocycles2.1 Intermolecular Reactions2.1.1 Cyclotrimerization of Alkynes2.1.2 [2+2+2] Cycloaddition of Two Different Alkynes2.1.3 [2+2+2] Cycloaddition of Alkynes/Alkenes with Alkenes/Enamides2.2 Partially Intramolecular [2+2+2] Cycloaddition Reactions2.2.1 Rhodium-Catalyzed [2+2+2] Cycloaddition2.2.2 Molybdenum-Catalyzed [2+2+2] Cycloaddition2.2.3 Cobalt-Catalyzed [2+2+2] Cycloaddition2.2.4 Ruthenium-Catalyzed [2+2+2] Cycloaddition2.2.5 Other Metal-Catalyzed [2+2+2] Cycloaddition2.3 Totally Intramolecular [2+2+2] Cycloaddition Reactions3 Formation of Heterocycles3.1 Cycloaddition of Alkynes with Nitriles3.2 Cycloaddition of 1,6-Diynes with Cyanamides3.3 Cycloaddition of 1,6-Diynes with Selenocyanates3.4 Cycloaddition of Imines with Allenes or Alkenes3.5 Cycloaddition of (Thio)Cyanates and Isocyanates3.6 Cycloaddition of 1,3,5-Triazines with Allenes3.7 Cycloaddition of Aldehydes with Enynes or Allenes/Alkenes3.8 Totally Intramolecular [2+2+2] Cycloaddition Reactions4 Conclusion

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Chemoselective Cobalt(I)-Catalyzed Cyclotrimerization of (Un)Symmetrical 1,3-Butadiynes for the Synthesis of 1,2,4-Regioisomers

Cited by 17 publications

References 39 publications

Late 3d Metal-Catalyzed (Cross-) Dimerization of Terminal and Internal Alkynes

Late 3d Metal-Catalyzed (Cross-) Dimerization of Terminal and Internal Alkynes

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

Recent Progress in Metal-Catalyzed [2+2+2] Cycloaddition Reactions

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