Metal- and Acid-Free Methyl Triflate Catalyzed Meyer–Schuster Rearrangement

Synthesis ◽  
2017 ◽  
Vol 49 (14) ◽  
pp. 3149-3156 ◽  
Author(s):  
Qingle Zeng ◽  
Lu Yang
Keyword(s):  
Carbonyl Compounds ◽  
Reaction Times ◽  
Mild Conditions ◽  
Broad Scope ◽  
Rearrangement Process ◽  
Methyl Triflate ◽  
Propargyl Alcohols

A novel metal- and acid-free preparation of synthetically useful α,β-unsaturated carbonyl compounds from propargyl alcohols has been realized. This Meyer–Schuster rearrangement process is effectively catalyzed by methyl triflate (20 mol%) to prepare a broad scope of conjugated E-enals and E-enones generally in good to excellent yields (up to 90%). This reaction procedure operates under mild conditions (70 °C), in air, with short reaction times (1 h). Moreover, a carbocation intermediate trapped by the solvent 2,2,2-trifluoroethanol was isolated during this transformation.

scholarly journals Proline Derived Ligands for the Titanium-Catalyzed Enantioselective Synthesis of Propargyl Alcohols in Presence of Diethylzinc

2019 ◽  
Author(s):  
Prianka Chohan ◽  
Giovanni Barrera ◽  
Kimberly Valdivia ◽  
Parminder Kaur
Keyword(s):  
Addition Reaction ◽  
Reaction Times ◽  
Catalyst System ◽  
Enantioselective Synthesis ◽  
Mild Conditions ◽  
Nucleophilic Addition Reaction ◽  
Proline Derivatives ◽  
Heterocyclic Aldehydes ◽  
Reaction Profile ◽  
Propargyl Alcohols

<div>A novel titanium/proline-derived catalyst system is reported for the enantioselective synthesis of propargyl alcohols. The reaction proceeded smoothly under mild conditions with efficient reaction times. A series of proline and proline-based ligands including Lproline, L-prolinol, trans-hydroxy-L-prolinol, and substituted trans hydroxy-L-proline derivatives were used to have a better stereocontrol on the reaction. Initially, lithium acetylide was employed to carry out the nucleophilic addition reaction, however poor reaction profile was achieved with poor enantioselectivities. When diethylzinc was used instead, high product yields (>85%) and moderate to high enantioselectivities were achieved (68-82%). Three different alkynes, aromatic as well as aliphatic, phenylacetylene, n-hexyne and 3,3-diethoxy-prop-1-yne were used to carry out the reaction with a series of different aromatic and heterocyclic aldehydes. Better reaction profiles were achieved with aromatic alkynes than with aliphatic ones.</div>

scholarly journals Proline Derived Ligands for the Titanium-Catalyzed Enantioselective Synthesis of Propargyl Alcohols in Presence of Diethylzinc

2019 ◽  
Author(s):  
Prianka Chohan ◽  
Giovanni Barrera ◽  
Kimberly Valdivia ◽  
Parminder Kaur
Keyword(s):  
Addition Reaction ◽  
Reaction Times ◽  
Catalyst System ◽  
Enantioselective Synthesis ◽  
Mild Conditions ◽  
Nucleophilic Addition Reaction ◽  
Proline Derivatives ◽  
Heterocyclic Aldehydes ◽  
Reaction Profile ◽  
Propargyl Alcohols

<div>A novel titanium/proline-derived catalyst system is reported for the enantioselective synthesis of propargyl alcohols. The reaction proceeded smoothly under mild conditions with efficient reaction times. A series of proline and proline-based ligands including Lproline, L-prolinol, trans-hydroxy-L-prolinol, and substituted trans hydroxy-L-proline derivatives were used to have a better stereocontrol on the reaction. Initially, lithium acetylide was employed to carry out the nucleophilic addition reaction, however poor reaction profile was achieved with poor enantioselectivities. When diethylzinc was used instead, high product yields (>85%) and moderate to high enantioselectivities were achieved (68-82%). Three different alkynes, aromatic as well as aliphatic, phenylacetylene, n-hexyne and 3,3-diethoxy-prop-1-yne were used to carry out the reaction with a series of different aromatic and heterocyclic aldehydes. Better reaction profiles were achieved with aromatic alkynes than with aliphatic ones.</div>

scholarly journals Synthesis of All-carbon Disubstituted Bicyclo[1.1.1]pentanes by Iron-Catalyzed Kumada CrossCoupling

2020 ◽  
Author(s):  
Jeremy Nugent ◽  
Bethany Shire ◽  
Dimitri F. J. Caputo ◽  
Helena D. Pickford ◽  
Frank Nightingale ◽  
...  
Keyword(s):  
Drug Design ◽  
Reaction Times ◽  
Cross Coupling ◽  
Grignard Reagents ◽  
Mild Conditions ◽  
Broad Scope ◽  
Wide Range ◽  
Harsh Conditions ◽  
General Method

1,3-Disubstituted bicyclo[1.1.1]pentanes (BCPs) are important motifs in drug design as surrogates for p-substituted arenes and alkynes. Access to all-carbon disubstituted BCPs via cross coupling has to date been limited to use of the BCP as the organometallic component, which restricts scope due to the harsh conditions typically required for the synthesis of metallated BCPs. Here we report a general method to access 1,3-C-disubstituted BCPs from 1-iodo-bicyclo[1.1.1]pentanes (iodo-BCPs) by direct iron-catalyzed crosscoupling with aryl and heteroaryl Grignard reagents. This chemistry represents the first general use of iodoBCPs as electrophiles in cross-coupling, and of Kumada coupling of tertiary iodides in general. Benefiting from short reaction times, mild conditions, and broad scope of the coupling partners, it enables the synthesis of a wide range of 1,3-C-disubstituted BCPs including various drug analogues.

scholarly journals Synthesis of All-carbon Disubstituted Bicyclo[1.1.1]pentanes by Iron-Catalyzed Kumada CrossCoupling

2020 ◽  
Author(s):  
Jeremy Nugent ◽  
Bethany Shire ◽  
Dimitri F. J. Caputo ◽  
Helena D. Pickford ◽  
Frank Nightingale ◽  
...  
Keyword(s):  
Drug Design ◽  
Reaction Times ◽  
Cross Coupling ◽  
Grignard Reagents ◽  
Mild Conditions ◽  
Broad Scope ◽  
Wide Range ◽  
Harsh Conditions ◽  
General Method

1,3-Disubstituted bicyclo[1.1.1]pentanes (BCPs) are important motifs in drug design as surrogates for p-substituted arenes and alkynes. Access to all-carbon disubstituted BCPs via cross coupling has to date been limited to use of the BCP as the organometallic component, which restricts scope due to the harsh conditions typically required for the synthesis of metallated BCPs. Here we report a general method to access 1,3-C-disubstituted BCPs from 1-iodo-bicyclo[1.1.1]pentanes (iodo-BCPs) by direct iron-catalyzed crosscoupling with aryl and heteroaryl Grignard reagents. This chemistry represents the first general use of iodoBCPs as electrophiles in cross-coupling, and of Kumada coupling of tertiary iodides in general. Benefiting from short reaction times, mild conditions, and broad scope of the coupling partners, it enables the synthesis of a wide range of 1,3-C-disubstituted BCPs including various drug analogues.

Microwave-Assisted Decarbonylation of Biomass-Derived Aldehydes Using Pd-Doped Hydrotalcites

2019 ◽  
Author(s):  
Nan An ◽  
Diana Ainembabazi ◽  
Kavya Samudrala ◽  
Christopher Reid ◽  
Kare Wilson ◽  
...  
Keyword(s):  
Heterogeneous Catalysts ◽  
Reaction Times ◽  
Inverse Correlation ◽  
Mulliken Charge ◽  
Metal Leaching ◽  
Carbonyl Carbon ◽  
Mild Conditions ◽  
Microwave Assisted ◽  
Biomass Processing ◽  
Alcohol Dehydrogenation

<p>Here we report the synthesis, characterization and activity of tunable Pd-doped hydrotalcites (Pd-HTs) for the decarbonylation of furfural, hydroxymethylfurfural (HMF), aromatic and aliphatic aldehydes under microwave conditions. The decarbonylation activity reported is a notable improvement over prior heterogeneous catalysts for this process. Furfural decarbonylation is optimized in a benign solvent compatible with biomass processing - ethanol, under relatively mild conditions and short reaction times. HMF selectively affords excellent yields of furfuryl alcohol with no humin formation, but longer reaction can also afford furan via tandem alcohol dehydrogenation and decarbonylation. Yields of substituted benzaldehydes are related to calculated Mulliken charge of the carbonyl carbon. The activity and selectivity differences can be traced to loading-dependent differences in Pd speciation on the catalysts. Poisoning studies show inverse correlation between Pd loading and metal leaching: Pd-HTs with lowest Pd loading, which consist of highly dispersed and oxidized Pd species, operate heterogeneously with negligible metal leaching. Recycling experiments are consistent with this trend, offering potential for further optimization to improve robustness.</p>

Enantioselective Radical Functionalization of Imines and Iminium Intermediates via Visible Light Photoredox Catalysis

Synthesis ◽  
2020 ◽  
Author(s):  
Jia-Jia Zhao ◽  
Hong-Hao Zhang ◽  
Shouyun Yu
Keyword(s):  
Visible Light ◽  
Asymmetric Synthesis ◽  
Carbonyl Compounds ◽  
Asymmetric Reduction ◽  
Chemical Transformations ◽  
Photoredox Catalysis ◽  
Radical Coupling ◽  
Mild Conditions ◽  
Iminium Ions ◽  
Radical Functionalization

Visible light photoredox catalysis has recently emerged as a powerful tool for the development of new and valuable chemical transformations under mild conditions. Visible-light promoted enantioselective radical transformations of imines and iminium intermediates provide new opportunities for the asymmetric synthesis of amines and asymmetric β-functionalization of unsaturated carbonyl compounds. In this review, the advance in the catalytic asymmetric radical functionalization of imines, as well as iminium intermediates, are summarized. 1 Introduction 2 The enantioselective radical functionalization of imines 2.1 Asymmetric reduction 2.2 Asymmetric cyclization 2.3 Asymmetric addition 2.4 Asymmetric radical coupling 3 The enantioselective radical functionalization of iminium ions 3.1 Asymmetric radical alkylation 3.2 Asymmetric radical acylation 4 Conclusion

scholarly journals Homocoupling of terminal alkynes catalyzed by CuCl under solvent-free conditions

2021 ◽  
pp. 174751982110325
Author(s):  
Yan Xiao ◽  
Jiyu Gao ◽  
Peng Chen ◽  
Guangliang Chen ◽  
Zicheng Li ◽  
...  
Keyword(s):  
Functional Group ◽  
Reaction Times ◽  
Environmentally Friendly ◽  
Solvent Free ◽  
Copper Salt ◽  
Terminal Alkynes ◽  
Mild Conditions ◽  
Solvent Free Conditions ◽  
Environmentally Friendly Process

A series of symmetrical 1,4-disubstituted buta-1,3-diynes is prepared with excellent yields (up to 95%) through homocoupling of terminal alkynes catalyzed by a copper salt under solvent-free conditions. This method provides an environmentally friendly process to prepare 1,3-diynes in short reaction times under mild conditions. Furthermore, the method is suitable for a wide substrate scope and has excellent functional group compatibility. The reaction can also be scaled up to gram level.

Efficient Synthesis of 3,4-Disubstituted 7-Azaindoles Employing SEM as a Dual Protecting–Activating Group

Synlett ◽  
2019 ◽  
Vol 30 (20) ◽  
pp. 2273-2278 ◽  
Author(s):  
Piroska Gyárfás ◽  
János Gerencsér ◽  
Warren S. Wade ◽  
László Ürögdi ◽  
Zoltán Novák ◽  
...  
Keyword(s):  
Functional Groups ◽  
Efficient Method ◽  
Reaction Times ◽  
Nucleophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Efficient Synthesis ◽  
Mild Conditions

An efficient method for nucleophilic aromatic substitution on 7-azaindoles has been developed. The reaction is facilitated by the unique dual influence of SEM as both protecting and activating group, permitting mild conditions and short reaction times that are compatible with sensitive functional groups. The method is suitable for the synthesis of a broad range of products, most notably ethers.

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