Crossed Pinacol Coupling Research Articles

Visible-Light-Antenna Ligand-Enabled Samarium-Catalyzed Reductive Transformations.

Although divalent Sm reagents are some of the most important single-electron transfer reagents for reductive transformations, their catalytic applications are challenging. In this study, a bidentate phosphine oxide ligand substituted with 9,10-diphenylanthracene as a visible-light antenna was designed for Sm-catalyzed reduction reactions under mild reaction conditions. Pinacol coupling of aryl ketones and aldehydes was developed with 1 mol % of Sm catalyst and organic amine (DIPEA) as a sacrificial mild reductant. Mechanistic studies suggest that the visible-light-antenna ligand coordinates to Sm(III) and reduces Sm(III) to Sm(II) under visible-light irradiation. The catalytic system is also applicable for cross-pinacol coupling and other single-electron reductive transformations, including aza-pinacol coupling, flavone dimerization, C-O bond cleavage, C-C ring-opening of cyclopropane, ketyl-olefin coupling, and cross-coupling of the ketyl radical with the α-amino radical.

Photocatalytic Cross-Pinacol Coupling Promoted by Carbon Dioxide.

Cross-pinacol coupling of two different carbonyl compounds was achieved through successive one-electron transfer processes under photocatalytic conditions. In the reaction, an umpoled anionic carbinol synthon was generated in situ to react nucleophilically with a second electrophilic carbonyl compound. We revealed that a CO2 additive promoted the photocatalytic generation of the carbinol synthon to suppress undesired radical dimerization. A wide variety of aromatic and aliphatic carbonyl substrates underwent the cross-pinacol coupling to afford the corresponding unsymmetric vicinal 1,2-diols, where even a combination of carbonyl reactants with similar structures such as two aldehydes and two ketones were also well tolerated with high cross-coupling selectivity.

Studies toward the Total Synthesis of Parvifolals A/B: An Intramolecular o-Quinone Methide [4 + 2]-Cycloaddition To Construct the Central Tetracyclic Core.

Two different approaches funded upon the intramolecular [4 + 2]-cycloaddition of in situ generated o-quinone methides have been explored to construct the central tetracyclic core of parvifolals A/B. At the outset, a cross-pinacol coupling of 2-formyl tri-O-methyl resveratrol with 4-methoxysalicylaldehyde followed by acid treatment was found to provide the desired tetracyclic core with an internal olefin. The requisite pendant aryl group has been introduced by a Pd-catalyzed direct coupling of corresponding diazonium salt.

ChemInform Abstract: A Novel Lanthanum Metal‐Assisted Reaction of Diaryl Ketones and Electrophiles.

Abstract A novel and efficient lanthanum metal-assisted carbon-carbon bond formation of diaryl ketones and various electrophiles, such as carbonyl compounds, esters, nitriles, and epoxides, has been developed. When diaryl ketones were allowed to react with dialkyl ketones in the presence of lanthanum metal and a catalytic amount of iodine, the cross pinacol coupling reaction proceeded to give the corresponding unsymmetrical 1,2-diols in moderate to good yields. α-Hydroxy ketones were prepared by the lanthanum metal-assisted reaction of diaryl ketones with esters or nitriles, followed by hydrolysis with aq HCl. It is interesting to note that for the epoxides, the coupling reaction proceeded via the Meinwald rearrangement of epoxides to give the corresponding 1,2-diols.

A novel lanthanum metal-assisted reaction of diaryl ketones and electrophiles

A novel and efficient lanthanum metal-assisted carbon-carbon bond formation of diaryl ketones and various electrophiles, such as carbonyl compounds, esters, nitriles, and epoxides, has been developed. When diaryl ketones were allowed to react with dialkyl ketones in the presence of lanthanum metal and a catalytic amount of iodine, the cross pinacol coupling reaction proceeded to give the corresponding unsymmetrical 1,2-diols in moderate to good yields. α-Hydroxy ketones were prepared by the lanthanum metal-assisted reaction of diaryl ketones with esters or nitriles, followed by hydrolysis with aq HCl. It is interesting to note that for the epoxides, the coupling reaction proceeded via the Meinwald rearrangement of epoxides to give the corresponding 1,2-diols.

Synthesis of Heterodinuclear Hemisalen Complexes on a Hexaarylbenzene Scaffold and their Application for the Cross‐Pinacol Coupling Reaction

Intermolecular cross-pinacol coupling reaction between aliphatic and aromatic aldehydes by using heterodinuclear hemisalen complexes 1cis with vanadium(V) and titanium(IV) on a hexaarylbenzene scaffold is reported. Our ligand design is based on the individual activation of two aldehydes by vanadium and titanium, which are positioned with a suitable space on the rigid scaffold. Ligands such as 1cis were synthesized by Diels-Alder addition and decarbonylation reaction, followed by condensation of dialdehyde 3cis with various aminophenols. The influence of the substituents on the ligands on the pinacol coupling reaction was investigated. As a result, the reductive coupling reaction between aliphatic and aromatic aldehydes by using a catalytic amount of 1cis in the presence of Me3 SiCl and Zn provided the corresponding cross-coupled 1,2-diol in good yields with high cross-selectivity.

The Electron-Way: Metal-Catalyzed Reductive Umpolung Reactions of Saturated and α,β-Unsaturated Carbonyl Derivatives

Reductive umpolung reactions of saturated and unsaturated carbonyl compounds enable the direct synthesis of 1,2-, 1,4-, 1,6-, etc. substituted carbon frameworks that are difficult to access by other methodologies. Herein, the evolution from stoichiometric to catalytic processes with high chemo-, regio- and stereoselectivity is discussed for each carbon–carbon bond connection type. At certain points, summaries of the known reaction conditions and discussions of the underlying mechanisms are included. 1 Introduction 1.1 Redox Umpolung 2 Catalyzed Pinacol Couplings and Related Reductive Homo-Dimerization Reactions 2.1 Evolution of Catalytic Systems 2.2 Diastereoselective Pinacol Coupling Reactions 2.3 Enantioselective Pinacol Coupling Reactions 2.4 Pinacol-Type Homo-Dimerization of Imines 2.5 Reductive Homo-Dimerization of Carboxylic Acid Derivatives 3 Cross-Coupling Reactions of Aldehydes, Ketones or Imines by Catalyzed Reductive Umpolung 3.1 Cross-Pinacol Coupling of Aldehydes and Ketones 3.2 Cross-Coupling of Carbonyl Derivatives with Michael Acceptors 3.3 Cross-Coupling of Carbonyls with a Carboxylic Acid Derivative or Nitrile 4 Reductive Coupling between α,β-Unsaturated Fragments 4.1 Reductive Cyclization Reactions 4.2 Intermolecular Reductive Homo-Coupling 4.3 Intermolecular Reductive Cross-Coupling 5 Conclusion

Samarium Diiodide Promoted Tandem β-Elimination and Cross-Pinacol Coupling: A New Access to 1-Vinyl-1,2-diols with Two Adjacent Quaternary Carbon Centers

A samarium diiodide promoted tandem β-elimination/cross-pinacol coupling was developed. A series of novel 1-vinyl-1,2-diols with two adjacent quaternary carbon centers were obtained in moderate to good yields. Possible reaction pathways are proposed.

Synthesis of three-dimensionally arranged bis-biphenol ligand on hexaaryl benzene scaffold and its application for cross-pinacol coupling reaction

The three-dimensionally arranged bis-biphenol ligand on a hexaaryl benzene scaffold for a dinuclear complex was synthesized by the Diels–Alder addition–decarbonylation reaction as a key step. Its preliminary studies on the titanium-induced cross-pinacol coupling reaction were performed based on step-by-step activation of two different aldehydes.

Electroreductive Crossed Pinacol Coupling of Aromatic Ketones with Aliphatic Ketones and Aldehydes.

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.

Electroreductive crossed pinacol coupling of aromatic ketones with aliphatic ketones and aldehydes

The intermolecular crossed pinacol coupling of aromatic ketones with aliphatic aldehydes and ketones was effected by electroreduction in the presence of chlorotrimethylsilane. The best result was obtained using a Pb cathode in Bu 4NPF 6/THF. The electroreduction of aromatic 1,4-, 1,5-, and 1,6-diketones under the same conditions gave four-, five-, and six-membered 1,2-diols with trans-stereoselectivity, while the reduction of these diketones with TiCl 4–Zn produced the cis-isomers of the same intramolecular crossed pinacol coupling products predominantly.

Trans‐Stereoselective Intramolecular Crossed Pinacol Coupling of Aromatic 1,4‐, 1,5‐, and 1,6‐Diketones by Electroreduction.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Trans-Stereoselective intramolecular crossed pinacol coupling of aromatic 1,4-, 1,5-, and 1,6-diketones by electroreduction

Electroreduction of aromatic 1,4-, 1,5-, and 1,6-diketones in the presence of chlorotrimethylsilane and triethylamine gave four-, five-, and six-membered 1,2-diols with trans-stereoselectivity.

Crossed Pinacol Coupling Reaction Between Aldehydes and Imines: A Rapid Access to 1,2‐Amino Alcohols.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Crossed Pinacol Coupling Reaction between Aldehydes and Imines:A Rapid Access to 1,2-Amino Alcohols

In the presence of zinc, boron trifluoride etherate, and methyltrichlorosilane, aldehydes and imines underwent a crossed pinacol coupling reaction to give 1,2-amino alcohols in good to excellent yields.

Asymmetric Synthesis of β-Amino Alcohols by Cross-Pinacol Coupling of Planar Chiral Ferrocenecarboxaldehydes with Imines

Asymmetric Synthesis of β-Amino Alcohols by Cross-Pinacol Coupling of Planar Chiral Ferrocenecarboxaldehydes with Imines