Chemoselective α-Methylenation of Aromatic Ketones Using the NaAuCl4/Selectfluor/DMSO System

Stereoselective Fluoroalkylacylation of Alkynes via Cooperative N-Heterocyclic Carbene/Palladium Catalysis

Herein, a cooperative N-heterocyclic carbene- and palladium-catalyzed three-component reaction of alkynes with aldehydes and fluoroalkyl iodides is developed. A series of biologically valuable CF2R-incorporated α-substituted enones was obtained in moderate to good yields. This mild catalytic method exhibits exclusive regio- and stereoselectivity, excellent functional group tolerance, and a broad substrate scope including terminal and internal alkynes. Mechanistic investigations disclose that this alkyne fluoroalkylacylation proceeds via a radical relay process in which vinyl iodides serve as putative reaction intermediates.

Efficient Approach for the Synthesis of Aryl Vinyl Ketones and Its Synthetic Application to Mimosifoliol with DFT and Autodocking Studies

An efficient and elegant method was developed for the preparation of substituted phenyl vinyl ketones using low-cost and commercially available ethyl chloroformate and diisopropylethylamine as reagents. This methodology was also applied to the synthesis of natural products such as mimosifoliol and quinolines. Frontier molecular orbital (FMO) studies on mimosifoliol were carried out to understand its chemical reactivity. Electron localization function (ELF) and localized orbital locator (LOL) analysis gave information about localized and delocalized electrons. Reduced density gradient (RDG) analysis gave information on steric, van der Waals, and hydrogen-bonding interactions. Molecular electrostatic potential (MEP) and Fukui functions gave information about nucleophilic and electrophilic attack. Nonlinear optical (NLO) analysis represented the mimosifoliol good NLO material. Molecular docking showed that the mimosifoliol compound had effectively inhibited the aspulvinone dimethylallyltransferase enzyme.

One-Pot Synthesis of Dihydropyrans via CO2 Reduction and Domino Knoevenagel/oxa-Diels-Alder Reactions

Catalytic CO₂ reduction with phenylsilane under solvent-free conditions was linked with the one-pot synthesis of 3,4-dihydropyrans from β-dicarbonyl compounds and styrenes. The synthesis includes three processes: (1) bis(silyl)acetal formation from CO₂ and phenylsilane and a domino reaction of (2) Knoevenagel condensation and (3) inverse-electron-demand oxa-Diels-Alder reaction. The first process was catalyzed by a pentanuclear Zn^II complex (0.07 mol %) to generate bis(silyl)acetals, which were hydrolyzed into formaldehyde to be used in the second step.

Synthesis of methylene-bridged α,β-unsaturated ketones: α-Csp3-H methylenation of aromatic ketones using Selectfluor as a mild oxidant

A three starting material four component reaction (3SM-4CR) is developed for the synthesis of α,β-unsaturated ketones and β-amino ketones in good yields. The reaction employs tetramethylethylenediamine (TMEDA) as a methylene and terminal olefin source, and Selectfluor as a mild oxidant. TMEDA worked as a dual synthon to provide two carbons in this metal-free transformation process. The scope and versatility of the methods have been demonstrated with 23 examples. A Selectfluor-promoted oxidative reaction mechanism is proposed based on the results of the experimental studies.

Direct α-methylenation of triazines to terminal olefins with DMA

We report an efficient metal (Cu or Ni)-catalysed α-methylenation of triazines to terminal olefins using DMA as a one-carbon source. Various substituted triazine derivatives are suitable for this reaction.

Palladium catalyzed desulfurative coupling of allyl sulfides with organoboronic acids

A palladium catalyzed desulfurative coupling of allylthioethers with organoboronic acids under mild reaction conditions is described.

Synthesis of 3-benzylidenetetrahydrofurans: Tf2O-catalyzed hydroxylation/cyclization of cyclopropanemethanols with DMSO

A formal hydroxylation/cyclization of cyclopropanemethanols with DMSO is described, which involves isomerization and cyclization under Tf₂O catalysis. This reaction undergoes ring-opening of the cyclopropane moiety to generate homoallylic alcohols, which react with DMSO to produce 3-benzylidenetetrahydrofurans. With various substituted groups on cyclopropanemethanols the reactions proceed smoothly and the desired 3-benzylidenetetrahydrofurans are obtained in moderate to good yields.

Recent Advances in the Application of Selectfluor as a "Fluorine-free" Functional Reagent in Organic Synthesis

Selectfluor, [1-chloromethyl-4-fluoro-1,4-diazoniabicyclo-[2.2.2]octane bis(tetrafluoroborate)], is not only an important electrophilic fluorinating agent but also a facile and efficient "fluorine-free" functional reagent in other organic reactions. In this Minireview, we will present a brief history of Selectfluor as a transition metal oxidant, fluorine cation and radical initiator in "fluorine-free" functionalizations over the last five years.

Palladium-Catalyzed Carbonylative Synthesis of α-Branched Enones from Aryl Iodides and Arylallenes

In this communication, an interesting carbonylation protocol for the preparation of α-branched enones has been established. Starting from readily available aryl iodides and allenes, with formic acid as the CO source and reductant, moderate to good yields of the desired enones were isolated. Although it is a carbonylation methodology, the use of a CO source can avoid the manipulation of CO gas directly. Notably, this procedure also presents the first example on carbonylative synthesis of α-branched enones.

Selectfluor™-catalyzed oxidative cyclization of ynamides enables facile synthesis of oxazolidine-2,4-diones

A Selectfluor™-catalyzed oxidative cyclization of ynamides employing DMSO as the solvent and oxidant was achieved, affording oxazolidine-2,4-diones in moderate to excellent yields with high chemo-selectivity. The method offers an attractive alternative to existing protocols.

A cascade oxidation/[4 + 1] annulation of sulfonium salts for synthesis of polyfunctional furans: DMSO as one carbon source

A novel DMSO-involved cascade reaction of stabilized sulfonium salts has been established for direct construction of polyfunctional furans.

Selectfluor-Mediated Benzo[d][1,2,3]Triazole Functionalisation of 4,4-Difluoro-4-Bora-3a,4a-Diaza-s-Indacene

8-Aryl-1-(1 H-benzo[ d][1,2,3]triazole-yl)-4,4-difluoro-4-bora-3a,4a-diaza- s-indacene and 8-aryl-3,5-di-(1 H-benzo[ d][1,2,3]triazole-yl)-4,4-difluoro-4-bora-3a,4a-diaza- s-indacene derivatives were synthesised by the reaction of 4,4-difluoro-4-bora-3a,4a-diaza- s-indacene with benzo[ d][1,2,3]triazole in the presence of Selectfluor in moderate to good yields. The reaction took placed regioselectively on the 3(5)-position carbon of 4,4-difluoro-4-bora-3a,4a-diaza- s-indacene, which was confirmed by X-ray analysis.