scholarly journals Selective Manganese-Catalyzed Semihydrogenation of Alkynes with in-situ Generated H2 from KBH4 and Methanol

2021 ◽  
Author(s):  
Ronald Farrar-Tobar ◽  
Stefan Weber ◽  
Zita Csendes ◽  
Antonio Ammaturo ◽  
Sarah Fleissner ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Dft Calculations ◽  
Functional Groups ◽  
Hydrogen Gas ◽  
Terminal Alkynes ◽  
Deuterium Labelling ◽  
Reaction Proceeds ◽  
Mechanistic Investigations

The selective semihydrogenation of alkynes with the Mn(I) alkyl catalyst fac-[Mn(dippe)(CO)3(CH2CH2CH3)] (dippe = 1,2-bis(di-iso-propylphosphino)ethane) as pre-catalyst is described. Hydrogen gas required for the hydrogenation is generated in situ upon alcoholysis of KBH4 with methanol. A series of aryl-aryl, aryl-alkyl, alkyl-alkyl and terminal alkynes were readily hydrogenated to yield E-alkenes in good to excellent isolated yields. The reaction proceeds at 90°C with catalyst loadings of 0.5 -2 mol%. The implemented protocol tolerates a variety of electron donating and electron withdrawing functional groups including halides, phenols, nitriles, unprotected amines and heterocycles. The reaction can be upscaled to the gram scale. Mechanistic investigations including deuterium labelling studies and DFT calculations were undertaken to provide a reasonable reaction mechanism showing that initially formed Z-isomer undergoes fast isomerization to afford the thermodynamically more stable E-isomer.

Manganese PNP-pincer catalyzed isomerization of allylic/homo-allylic alcohols to ketones – activity, selectivity, efficiency

2019 ◽  
Vol 9 (22) ◽  
pp. 6327-6334 ◽  
Author(s):  
Tian Xia ◽  
Brian Spiegelberg ◽  
Zhihong Wei ◽  
Haijun Jiao ◽  
Sergey Tin ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Pincer Complexes ◽  
Allylic Alcohols ◽  
Deuterium Labelling ◽  
Reaction Proceeds

Manganese PNP pincer complexes are excellent catalysts for the isomerization of allylic alcohols to the ketones. The reaction proceeds via a dehydrogenation/hydrogenation mechanism as shown by DFT calculations and deuterium labelling.

Titanacyclopropanes as versatile intermediates for carbon-carbon bond formation in reactions with unsaturated compounds

2000 ◽  
Vol 72 (9) ◽  
pp. 1715-1719 ◽  
Author(s):  
O. G. Kulinkovich
Keyword(s):  
Reaction Mechanism ◽  
Bond Formation ◽  
Grignard Reagents ◽  
Allylic Alcohols ◽  
Ethylmagnesium Bromide ◽  
Carbon Bond ◽  
Unsaturated Compounds ◽  
Carbon Carbon Bond ◽  
Reaction Proceeds

Dialkoxytitanacyclopropane intermediates [or titanium (II)-olefin complexes] generated in situ from ethylmagnesium bromide and titanium (IV) isopropoxide react with allylic alcohols and allylic ethers to afford SN2' allylic ethylation products. The reaction proceeds with high regioselectivity and with low to high trans-/cis-stereoselectivity. This observation and others suggest a reaction mechanism involving an EtMgBr-initiated formation of titanacyclopentane ate complex 10 from titanacyclopropane-olefin complex 7 as a key step. Based on this assumption, a modified mechanism of titanium-mediated cyclopropanation of esters with Grignard reagents is proposed.

Intramolecular Cycloaddition Approach to Fused Pyrazoles: Access to 4,5-Dihydro-2H-pyrazolo[4,3-c]quinolines, 2,8-Dihydroindeno[2,1-c]pyrazoles, and 4,5-Dihydro-2H-benzo[e]indazoles

Synthesis ◽  
2017 ◽  
Vol 50 (07) ◽  
pp. 1511-1520 ◽  
Author(s):  
Chinmay Chowdhury ◽  
Moumita Jash ◽  
Bimolendu Das ◽  
Suparna Sen
Keyword(s):  
Reaction Mechanism ◽  
Dft Calculations ◽  
Functional Groups ◽  
Efficient Method ◽  
Diazo Compound ◽  
Dipolar Cycloaddition ◽  
Reaction Sequence ◽  
Intramolecular Cycloaddition ◽  
Aromatic Substrate ◽  
Fused Pyrazoles

A straightforward and efficient method for the synthesis of pyrazoles fused with 1,2,3,4-tetrahydroquinoline, 2,3-dihydro-1H-indene­, or 1,2,3,4-tetrahydronaphthalene involves the formation of the tosylhydrazone from an aromatic substrate carrying aldehyde and acetylenic functionalities at appropriate positions, followed by base-promoted generation of the diazo compound and subsequent intramolecular 1,3-dipolar cycloaddition. A number of functional groups were found to be compatible for this reaction sequence and yields were moderate to very good (44–95%). A plausible reaction mechanism supported by DFT calculations has been provided to explain the formation of products.

Catalytic Sulfone Upgrading Reaction with Alcohols via Ru(II)

2019 ◽  
Author(s):  
Tomas Vojkovsky ◽  
Shubham Deolka ◽  
Saiyyna P. Stepanova ◽  
Michael C. Roy ◽  
Eugene Khaskin
Keyword(s):  
Functional Groups ◽  
Secondary Alcohol ◽  
Value Added ◽  
Catalytic Dehydrogenation ◽  
Reaction Conditions ◽  
Stoichiometric Amount ◽  
Reaction Proceeds ◽  
One Step ◽  
Value Added Products

<a>Sulfones and sulfonamides with an α-CH bond can be easily alkylated by aliphatic alcohols to add the carbon skeleton of the alcohol via a one-step, Ru(II) catalyzed redox neutral reaction. The reaction requires a sub-stoichiometric amount of base and produces only water as a byproduct. A number of pharmaceutically relevant functional groups such as piperidine, morpholine, etc. are well tolerated under the reaction conditions to give higher value-added products in one step from widely available substrates. The reaction proceeds through a sulfone carbanion addition to an in-situ generated aldehyde formed via catalytic dehydrogenation and subsequent catalyst mediated replacement of the secondary alcohol by hydrogen.</a>

scholarly journals Direct C–H Alpha Arylation of Enones with ArI(O2CR)2 Reagents

2019 ◽  
Author(s):  
Felipe Cesar Sousa e Silva ◽  
Nguyen T Van ◽  
Sarah Wengryniuk
Keyword(s):  
Claisen Rearrangement ◽  
Bond Formation ◽  
Hypervalent Iodine ◽  
Enol Ethers ◽  
Silyl Enol Ethers ◽  
Metal Free ◽  
Wide Range ◽  
Reaction Proceeds ◽  
Mechanistic Investigations

Herein, we report the metal-free direct C–H arylation of enones mediated by hypervalent iodine reagents. The reaction proceeds via a reductive iodonium Claisen rearrangement of <i>in situ </i>b-pyridinium silyl enol ethers. The aryl groups are derived from ArI(O<sub>2</sub>CCF<sub>3</sub>)<sub>2</sub> reagents, which are readily accessed from the parent iodoarenes. It is tolerant of a wide range of substitution patterns and the incorporated arenes maintain the valuable iodine functional handle. Mechanistic investigations implicate arylation via an umpoled “enolonium” species and that the presence of a b-pyridinium moiety is critical for desired C–C bond formation.

scholarly journals Ge‐Substituted Hierarchical Ferrierite for n ‐Pentane Cracking to Light Olefins: Mechanistic Investigations via In‐situ DRIFTS Studies and DFT Calculations

ChemCatChem ◽  
2022 ◽  
Author(s):  
Chadatip Rodaum ◽  
Anawat Thivasasith ◽  
Ploychanok Iadrat ◽  
Pinit Kidkhunthod ◽  
Sitthiphong Pengpanich ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Light Olefins ◽  
In Situ Drifts ◽  
Mechanistic Investigations

Ge‐substituted hierarchical ferrierite for n‐pentane cracking to light olefins: Mechanistic  investigations via In‐situ DRIFTS studies and DFT calculations

ChemCatChem ◽  
2021 ◽  
Author(s):  
Chadatip Rodaum ◽  
Anawat Thivasasith ◽  
Ploychanok Iadrat ◽  
Pinit Kidkhunthod ◽  
Sitthiphong Pengpanich ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Light Olefins ◽  
In Situ Drifts ◽  
Mechanistic Investigations

Catalytic Sulfone Upgrading Reaction with Alcohols via Ru(II)

2019 ◽  
Author(s):  
Tomas Vojkovsky ◽  
Shubham Deolka ◽  
Saiyyna P. Stepanova ◽  
Michael C. Roy ◽  
Eugene Khaskin
Keyword(s):  
Functional Groups ◽  
Secondary Alcohol ◽  
Value Added ◽  
Catalytic Dehydrogenation ◽  
Reaction Conditions ◽  
Stoichiometric Amount ◽  
Reaction Proceeds ◽  
One Step ◽  
Value Added Products

<a>Sulfones and sulfonamides with an α-CH bond can be easily alkylated by aliphatic alcohols to add the carbon skeleton of the alcohol via a one-step, Ru(II) catalyzed redox neutral reaction. The reaction requires a sub-stoichiometric amount of base and produces only water as a byproduct. A number of pharmaceutically relevant functional groups such as piperidine, morpholine, etc. are well tolerated under the reaction conditions to give higher value-added products in one step from widely available substrates. The reaction proceeds through a sulfone carbanion addition to an in-situ generated aldehyde formed via catalytic dehydrogenation and subsequent catalyst mediated replacement of the secondary alcohol by hydrogen.</a>

scholarly journals Direct C–H Alpha Arylation of Enones with ArI(O2CR)2 Reagents

2019 ◽  
Author(s):  
Felipe Cesar Sousa e Silva ◽  
Nguyen T Van ◽  
Sarah Wengryniuk
Keyword(s):  
Claisen Rearrangement ◽  
Bond Formation ◽  
Hypervalent Iodine ◽  
Enol Ethers ◽  
Silyl Enol Ethers ◽  
Metal Free ◽  
Wide Range ◽  
Reaction Proceeds ◽  
Mechanistic Investigations

Herein, we report the metal-free direct C–H arylation of enones mediated by hypervalent iodine reagents. The reaction proceeds via a reductive iodonium Claisen rearrangement of <i>in situ </i>b-pyridinium silyl enol ethers. The aryl groups are derived from ArI(O<sub>2</sub>CCF<sub>3</sub>)<sub>2</sub> reagents, which are readily accessed from the parent iodoarenes. It is tolerant of a wide range of substitution patterns and the incorporated arenes maintain the valuable iodine functional handle. Mechanistic investigations implicate arylation via an umpoled “enolonium” species and that the presence of a b-pyridinium moiety is critical for desired C–C bond formation.

Mn(III)-Mediated Facile Access to Polysubstituted α-Naphthols from β-Keto Ester Derivatives and Terminal Alkynes

Synthesis ◽  
2020 ◽  
Vol 52 (13) ◽  
pp. 1959-1968
Author(s):  
Yuzhu Yang ◽  
Weidong Pan ◽  
Lisheng He ◽  
Fei Li ◽  
Xiaolan Liu
Keyword(s):  
Radical Cyclization ◽  
Terminal Alkynes ◽  
Keto Ester ◽  
Keto Esters ◽  
Mild Conditions ◽  
Cyclization Process ◽  
Reaction Proceeds ◽  
Mechanistic Investigations

A novel manganese-mediated reaction for the synthesis of polysubstituted α-naphthols has been developed from β-keto esters and terminal alkynes. This system holds the advantages of readily available starting materials and mild conditions. Mechanistic investigations revealed that this reaction proceeds via a tandem radical cyclization process.

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