scholarly journals Selective Manganese-Catalyzed Dimerization and Cross-Coupling of Terminal Alkynes

2021 ◽  
Author(s):  
Stefan Weber ◽  
Luis F. Veiros ◽  
Karl Kirchner
Keyword(s):  
Dft Calculations ◽  
Precious Metal ◽  
Bond Cleavage ◽  
Cross Coupling ◽  
Metal Catalyst ◽  
Catalyst Loading ◽  
Terminal Alkynes ◽  
Migratory Insertion ◽  
Earth Abundant ◽  
First Time

<div>For the first time, an efficient manganese-catalyzed dimerization of terminal alkynes to afford 1,3-enynes is described. This reaction is atom economic, implementing an inexpensive, earth abundant non-precious metal catalyst. The pre-catalyst is the bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn-alkyl bond to yield an acyl intermediate which undergoes rapid C-H bond cleavage of the alkyne forming an active Mn(I) acetylide catalyst [Mn(dippe)(CO)2(C≡CPh)(η2-HC≡CPh)] together with liberated butanal. A range of aromatic and aliphatic terminal alkynes were efficiently and selectively converted into head-to-head Z-1,3-enynes and head-to-tail gem-1,3-enynes, respectively, in good to excellent yields. Moreover, cross-coupling of aromatic and aliphatic alkynes yields selectively head-to-tail gem-1,3-enynes. In all cases, the reactions were performed at 70 °C with a catalyst loading of 1-2 mol %. A mechanism based on DFT calculations is presented.</div><div><br></div>

scholarly journals Selective Manganese-Catalyzed Dimerization and Cross-Coupling of Terminal Alkynes

2021 ◽  
Author(s):  
Stefan Weber ◽  
Luis F. Veiros ◽  
Karl Kirchner
Keyword(s):  
Dft Calculations ◽  
Precious Metal ◽  
Bond Cleavage ◽  
Cross Coupling ◽  
Metal Catalyst ◽  
Catalyst Loading ◽  
Terminal Alkynes ◽  
Migratory Insertion ◽  
Earth Abundant ◽  
First Time

<div>For the first time, an efficient manganese-catalyzed dimerization of terminal alkynes to afford 1,3-enynes is described. This reaction is atom economic, implementing an inexpensive, earth abundant non-precious metal catalyst. The pre-catalyst is the bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn-alkyl bond to yield an acyl intermediate which undergoes rapid C-H bond cleavage of the alkyne forming an active Mn(I) acetylide catalyst [Mn(dippe)(CO)2(C≡CPh)(η2-HC≡CPh)] together with liberated butanal. A range of aromatic and aliphatic terminal alkynes were efficiently and selectively converted into head-to-head Z-1,3-enynes and head-to-tail gem-1,3-enynes, respectively, in good to excellent yields. Moreover, cross-coupling of aromatic and aliphatic alkynes yields selectively head-to-tail gem-1,3-enynes. In all cases, the reactions were performed at 70 °C with a catalyst loading of 1-2 mol %. A mechanism based on DFT calculations is presented.</div><div><br></div>

scholarly journals Rethinking Basic Concepts - Hydrogenation of Alkenes Catalyzed by Bench-Stable Alkyl Mn(I) Complexes

2019 ◽  
Author(s):  
Stefan Weber ◽  
Berthold Stöger ◽  
Luis F. Veiros ◽  
Karl Kirchner
Keyword(s):  
Dft Calculations ◽  
Molecular Hydrogen ◽  
Precious Metal ◽  
Hydrogen Pressure ◽  
Environmentally Benign ◽  
Metal Catalyst ◽  
Catalyst Loading ◽  
Migratory Insertion ◽  
Earth Abundant ◽  
Basic Concepts

An efficient additive-free manganese-catalyzed hydrogenation of alkenes to alkanes with molecular hydrogen is described. This reaction is environmentally benign and atom economic, implementing an inexpensive, earth abundant non-precious metal catalyst. The most efficient pre-catalyst is the bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn-alkyl bond to yield an acyl intermediate which undergoes rapid hydrogenolysis to form the active 16e Mn(I) hydride catalyst [Mn(dippe)(CO)2(H)]. A range of mono- and disubstituted alkenes were efficiently converted into alkanes in good to excellent yields. The hydrogenation of 1-alkenes and 1,1-disubstituted alkenes proceeds at 25 oC, while 1,2-disubstituted alkenes require a reaction temperature of 60oC. In all cases, a catalyst loading of 2 mol % and a hydrogen pressure of 50 bar was applied. A mechanism based on DFT calculations is presented.<br>

scholarly journals Rethinking Basic Concepts - Hydrogenation of Alkenes Catalyzed by Bench-Stable Alkyl Mn(I) Complexes

2019 ◽  
Author(s):  
Stefan Weber ◽  
Berthold Stöger ◽  
Luis F. Veiros ◽  
Karl Kirchner
Keyword(s):  
Dft Calculations ◽  
Molecular Hydrogen ◽  
Precious Metal ◽  
Hydrogen Pressure ◽  
Environmentally Benign ◽  
Metal Catalyst ◽  
Catalyst Loading ◽  
Migratory Insertion ◽  
Earth Abundant ◽  
Basic Concepts

An efficient additive-free manganese-catalyzed hydrogenation of alkenes to alkanes with molecular hydrogen is described. This reaction is environmentally benign and atom economic, implementing an inexpensive, earth abundant non-precious metal catalyst. The most efficient pre-catalyst is the bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn-alkyl bond to yield an acyl intermediate which undergoes rapid hydrogenolysis to form the active 16e Mn(I) hydride catalyst [Mn(dippe)(CO)2(H)]. A range of mono- and disubstituted alkenes were efficiently converted into alkanes in good to excellent yields. The hydrogenation of 1-alkenes and 1,1-disubstituted alkenes proceeds at 25 oC, while 1,2-disubstituted alkenes require a reaction temperature of 60oC. In all cases, a catalyst loading of 2 mol % and a hydrogen pressure of 50 bar was applied. A mechanism based on DFT calculations is presented.<br>

scholarly journals Iron-Catalyzed Silylation of Alcohols by Transfer Hydrosilylation with Silyl Formates

Synlett ◽  
2017 ◽  
Vol 28 (18) ◽  
pp. 2473-2477 ◽  
Author(s):  
Thibault Cantat ◽  
Timothé Godou ◽  
Clément Chauvier ◽  
Pierre Thuéry
Keyword(s):  
Transition Metal ◽  
Iron Catalyst ◽  
Metal Catalyst ◽  
Reaction Conditions ◽  
Transition Metal Catalyst ◽  
Earth Abundant ◽  
First Time

An iron catalyst is shown for the first time to promote transfer hydrosilylation with silyl formates and is utilized for the silylation of alcohols. Attractive features of this protocol include the use of an earth-abundant transition-metal catalyst, mild reaction conditions, and the release of gases as the only byproducts (H2 and CO2).

Nickel-Promoted Reductive Cyclization Cascade: A Short Synthesis of a New Aromatic Strigolactone Analogue

Synthesis ◽  
2017 ◽  
Vol 49 (16) ◽  
pp. 3576-3581 ◽  
Author(s):  
Yu Peng ◽  
Jian Xiao ◽  
Ya-Wen Wang
Keyword(s):  
Dft Calculations ◽  
Cross Coupling ◽  
Stereospecific Synthesis ◽  
Reductive Cyclization ◽  
Conformation Analysis ◽  
Short Synthesis ◽  
First Time

A stereospecific synthesis of the tetrahydro-2H-indeno[1,2-b]furan skeleton, which is embedded in bioactive aromatic strigolactones such as GR24, is realized by a nickel-mediated tandem cross-coupling for the first time. The observed cis-stereoselectivity during the intramolecular formation of the Csp3–Csp2 bond is rationalized through conformation analysis and DFT calculations.

Pd-catalyzed cross-coupling of terminal alkynes with ene-yne-ketones: access to conjugated enynes via metal carbene migratory insertion

2015 ◽  
Vol 51 (56) ◽  
pp. 11233-11235 ◽  
Author(s):  
Ying Xia ◽  
Zhen Liu ◽  
Rui Ge ◽  
Qing Xiao ◽  
Yan Zhang ◽  
...  
Keyword(s):  
Bond Formation ◽  
Cross Coupling ◽  
Terminal Alkynes ◽  
Conjugated Enynes ◽  
Migratory Insertion ◽  
Insertion Process

Pd-catalyzed oxidative cross-coupling of terminal alkynes with ene-yne-ketones has been developed, in which the ene-yne-ketones are served as carbene precursors and metal carbene migratory insertion process is the key step for C–C bond formation.

Microwave-assisted Cobalt-copper Dual Catalyzed Ligand Free C-Se Cross-coupling

2020 ◽  
Vol 7 (2) ◽  
pp. 157-163
Author(s):  
Debasish Kundu ◽  
Anup Roy ◽  
Subir Panja ◽  
Raj K. Singh
Keyword(s):  
Transition Metal ◽  
Cross Coupling ◽  
Building Blocks ◽  
Transition Metal Catalysts ◽  
Metal Catalyst ◽  
Co Catalyst ◽  
Ligand Free ◽  
Transition Metal Catalyzed ◽  
Metal Catalyzed ◽  
First Time

Background: Organoselenides are important building blocks of several biologically important molecules and natural products. Several protocols have been developed by chemists for their synthesis. Transition metal-catalyzed cross-coupling is a powerful tool for this purpose in the last two decades. Various transition metal catalysts e.g. Pd, Ni, Cu, In etc. have been used for performing C-Se cross-coupling in the presence or absence of ligands. Objective: Development of a sustainable protocol for transition metal-catalyzed C-Se cross-coupling is the main objective of this research. Recently, Cobalt has been applied as a cheap and sustainable transition metal catalyst in several organic reactions. This protocol is focused on applying cobalt salt as a catalyst for performing C-Se cross-coupling for the first time. Methods: Co(acac)2 has been successfully employed for performing Se-arylations in the presence of CuI, which acts as a co-catalyst under microwave irradiation. NMP was used as solvent and KOH as a reductant in this reaction. Results: Both iodo-and bromoarenes have been used to perform C-Se cross-coupling with diaryl diselenide under this Co/Cu dual catalytic system. The reaction was successful with both electrondonating and withdrawing groups in ortho-, meta-, and para-positions in the aromatic ring of Bromo and iodoarenes. Conclusion: This is an effective protocol for the preparation of organoselenides, catalyzed by cobalt in the presence of copper. The mechanism has been established by several experimental techniques.

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