Reductive Coupling Of Carbonyl Compounds Research Articles

Dual Photoredox and Titanium Catalyzed Regioselective Allenylation of Aldehydes via Reductive Radical‐Polar Crossover

Comprehensive SummaryThe direct reductive coupling of carbonyl compounds with propargyl halides is a powerful and reliable tool in the synthesis of α‐allenols. However, stoichiometric metal reductants, harsh reaction conditions and a variety of additional additives are required in the traditional strategies. Additionally, the reactivity and regioselectivity control remains an elusive challenge. Herein, we developed the Ti‐catalyzed regioselective reductive coupling of readily available aldehydes and racemic propargyl bromides to rapidly access a wide range of α‐allenols. This method proceed efficiently in a reductive radical‐polar crossover manner featuring mild conditions, excellent regioselectivity control, broad substrate scope, and eco‐friendliness. Preliminary mechanistic studies support the radical‐involved catalytic cycle. And the DFT calculations demonstrate that the regioselectivity is determined by the Zimmerman‐Traxler‐type transition states.

Photo-catalyst-free photomediated pinacol coupling of ketones/aldehydes by formate at room temperature

In this work, a highly effective metal-free and photo-catalyst-free method for the reductive coupling of carbonyl compounds to produce pinacols using formate under photoirradiation has been reported.

A versatile catalyst-free redox system mediated by carbon dioxide radical and dimsyl anions

The development of new, efficient ways to initiate redox events has long been a goal in organic synthesis. A redox system mediated by carbon dioxide radical and dimsyl anions is demonstrated and a variety of transformations, including hydrocarboxylation, hydroxycarboxylation, Birch reduction, and three-component reductive coupling of carbonyl compounds, amines, and cyanopyridines, are achieved in a catalyst-free fashion using this method, giving valuable acids, saturated skeletons, and α-pyridyl amines in high efficiency. This strategy promises wide applications in other types of reactions and complements current photoredox catalysis methodologies.

Photoinduced umpolung addition of carbonyl compounds with α,β-unsaturated esters enables the polysubstituted γ-lactone formation.

We herein report the photoinduced intermolecular umpolung addition of aromatic ketones/aldehydes with α,β-unsaturated esters via ketyl radical intermediates. Following an intramolecular transesterification, a variety of γ-lactone derivatives are readily accessed. Mechanistic investigations demonstrate the significant role of Hantzsch ester, which serves both as the electron and proton donor.

The Fascinating World of Phosphanylphosphonates: From Acetylenic Phosphaalkenes to Reductive Aldehyde Couplings

This account highlights the versatility of phosphanylphosphonates, which can be used for the preparation of phosphorus-containing π-systems and as reagents for the reductive coupling of carbonyl compounds to alkenes. Phosphanylphosphonates with metal fragments coordinated to the P-lone pair have been known for a long time and they have been used for the synthesis of phosphaalkenes by means of the phospha-Horner–Wadsworth–Emmons reaction. With the original aim of incorporating phosphorus heteroatoms into classical all-carbon ethynylethene scaffolds, we entered the field of phosphanylphosphonates with the discovery that these compounds engage in complex cascade reactions with acetylenic ketones, forming 1,2-oxaphospholes, cumulenes, and bisphospholes. Later, we synthesized the first metal-free phosphanylphosphonate, which reacts with aldehydes to yield phosphaalkenes, but gives phospholones when diacetylenic ketones are used as substrates. In the final part of the account, we outline our discovery and the development of an unprecedented carbonyl–carbonyl cross-coupling reaction. This protocol offers a straightforward method for the synthesis of nonsymmetric 1,2-disubstituted alkenes directly from two dissimilar aldehydes.1 Combining Acetylenes with Phosphaalkenes2 Synthetic Examples of Acetylenic Phosphaalkenes3 The Phospha-Horner–Wadsworth–Emmons Approach to Phosphaalkenes3.1 Metal-Coordinated Phosphanylphosphonates3.2 Mechanism of the Phospha-Horner–Wadsworth–Emmons Reaction3.3 The First Metal-Free Phosphanylphosphonate and Its Reactivity with Aldehydes4 Reactions with Acetylenic Ketones4.1 Metal-Coordinated Phosphanylphosphonate and Monoacetylenic Ketones4.2 Metal-Coordinated Phosphanylphosphonate and Diacetylenic Ketones4.3 Metal-Free Phosphanylphosphonate and Diacetylenic Ketones5 Metal-Free Phosphanylphosphonate as a Coupling Reagent for Aldehydes6 E-Alkenes by the Reductive Coupling of Two Aldehydes7 Conclusions and Outlook

Air-Stable Blue Phosphorescent Tetradentate Platinum(II) Complexes as Strong Photo-Reductant.

Strong photo-reductants have applications in photo-redox organic synthesis involving reductive activation of C-X(halide) and C=O bonds. We report herein air-stable PtII complexes supported by tetradentate bis(phenolate-NHC) ligands having peripheral electron-donating N-carbazolyl groups. Photo-physical, electrochemical, and computational studies reveal that the presence of N-carbazolyl groups enhances the light absorption and redox reversibility because of its involvement into the frontier MOs in both ground and excited states, making the complexes robust strong photo-reductant with E([Pt]+/ *) over -2.6 V vs. Cp2 Fe+/0 . The one-electron reduced [Pt]- species are stronger reductants with EPC ([Pt]0/- ) up to -3.1 V vs. Cp2 Fe+/0 . By virtue of the strong reducing nature of these species generated upon light excitation, they can be used in light-driven reductive coupling of carbonyl compounds and reductive debromination of a wide range of unactivated aryl bromides.

Air‐Stable Blue Phosphorescent Tetradentate Platinum(II) Complexes as Strong Photo‐Reductant

AbstractStrong photo‐reductants have applications in photo‐redox organic synthesis involving reductive activation of C−X(halide) and C=O bonds. We report herein air‐stable PtII complexes supported by tetradentate bis(phenolate‐NHC) ligands having peripheral electron‐donating N‐carbazolyl groups. Photo‐physical, electrochemical, and computational studies reveal that the presence of N‐carbazolyl groups enhances the light absorption and redox reversibility because of its involvement into the frontier MOs in both ground and excited states, making the complexes robust strong photo‐reductant with E([Pt]+/*) over −2.6 V vs. Cp2Fe+/0. The one‐electron reduced [Pt]− species are stronger reductants with EPC([Pt]0/−) up to −3.1 V vs. Cp2Fe+/0. By virtue of the strong reducing nature of these species generated upon light excitation, they can be used in light‐driven reductive coupling of carbonyl compounds and reductive debromination of a wide range of unactivated aryl bromides.

Reductive coupling of carbonyl compounds promoted by cobalt or titanium nanoparticles

The reaction of a series of aldehydes and ketones with readily prepared cobalt or titanium nanoparticles, under mild reaction conditions, led to the obtention of different reductive dimerization products depending on the nature of the transition metal used. Cobalt nanoparticles (CoNPs) allowed the selective transformation of the starting carbonyl compounds into vicinal diols, whereas the reaction promoted by titanium nanoparticles (TiNPs) led to the formation of the corresponding alkenes. In this last case, the use of trimethylsilyl chloride (TMSCl) as additive, at 0 oC, also allowed the obtention of vicinal diols after acidic aqueous work-up.

ChemInform Abstract: Catalytic Reductive Coupling of Carbonyl Compounds: The Pinacol Coupling Reaction and Beyond

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

SiCl4—Zn‐Induced Reductive Coupling of Carbonyl Compounds: Novel and Efficient Routes for One‐Pot Syntheses of 1,2,3‐Triaryl‐2‐propen‐1‐ones and Pinacolones at Room Temperature.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Ionic‐Liquid‐Influenced Expeditious and Stereoselective Synthesis of Olefins

1‐Butyl‐3‐methylimidazolium chloroaluminate, [bmim]Cl·.AlCl3 (molar fraction, N=0.67), ionic liquid has been used in combination with metallic Zn for the reductive coupling of carbonyl compounds to synthesize symmetrical olefins, with the Z‐isomer formed predominantly. The ionic liquid played a dual role of Lewis acid catalyst and solvent.

SiCl 4–Zn induced reductive coupling of carbonyl compounds: novel and efficient routes for one-pot syntheses of 1,2,3-triaryl-2-propen-1-ones and pinacolones at room temperature

An unprecedented one-pot reductive trimerization of aromatic aldehydes to 1,2,3-triaryl-2-propen-1-ones as well as tandem reductive coupling-rearrangements of aryl ketones to pinacolone analogues was efficiently achieved using tetrachlorosilane–zinc at room temperature.

Low‐Valent Titanium‐Mediated Reductive Coupling of Carbonyl Compounds

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Low-Valent Titanium-Mediated Reductive Coupling of Carbonyl Compounds

This account describes recent organic synthesis applications and developments in mechanistic understanding of low-valent titanium-mediated reductive coupling of carbonyl compounds. Pinacol and McMurry coupling reactions are among the most powerful methods for constructing carbon-carbon bonds, and have served as the key step in the synthesis of various natural and synthetic products. The range and selectivity of low-valent titanium reagents that mediate pinacol and McMurry reactions are discussed. The nature of their active species is discussed in conjunction with relevant chemistry of well-characterized low-valent titanium complexes, all of which serve to inform current understanding of the reaction mechanisms.

Samarium/N‐Bromosuccinimide‐Induced Reductive Dimerization of Carbonyl Compounds.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Samarium/ N-bromosuccinimide-induced reductive dimerization of carbonyl compounds

Stereoselective reductive coupling of carbonyl compounds has been achieved using samarium/ N-bromosuccinimide in methanol. The combination of these agents has proved a powerful addition to the arsenal of samarium-based reductants currently utilized.

Reductive Etherification of Carbonyl Compounds with Alkyl Trimethylsilylethers Using Polymethylhydrosiloxane (PMHS) and Catalytic B(C6F5)3.

Abstract A facile synthesis of symmetrical and unsymmetrical ethers is achieved by reductive coupling of carbonyl compounds with alkoxysilanes. This reaction is performed using inert polymethylhydrosiloxane as the hydride source and B(C 6 F 5 ) 3 as the catalytic activator of the PMHS.

Reductive etherification of carbonyl compounds with alkyl trimethylsilylethers using polymethylhydrosiloxane (PMHS) and catalytic B(C6F5)3

A facile synthesis of symmetrical and unsymmetrical ethers is achieved by reductive coupling of carbonyl compounds with alkoxysilanes. This reaction is performed using inert polymethylhydrosiloxane as the hydride source and B(C6F5)3 as the catalytic activator of the PMHS.

A Novel, Solventless Reductive Coupling of Carbonyl Compounds by Alkali Metals, Catalyzed by Bromobenzene.

A Novel, Solventless Reductive Coupling of Carbonyl Compounds by Alkali Metals, Catalyzed by Bromobenzene.

A novel, solventless reductive coupling of carbonyl compounds by alkali metals, catalysed by bromobenzene

Catalysed by bromobenzene, alkali metals including Li, Na, and K can mediate the reductive coupling of carbonyl compounds under mild, solventless conditions to furnish the corresponding pinacol products.