Transformations of Aryl Ketones via Ligand-Promoted C−C Bond Activation

The coupling of aromatic electrophiles (aryl halides, aryl ethers, aryl acids, aryl nitriles etc.) with nucleophiles is a core methodology for the synthesis of aryl compounds. Transformations of aryl ketones in an analogous manner via carbon–carbon bond activation could greatly expand the toolbox for the synthesis of aryl compounds due to the abundance of aryl ketones. An exploratory study of this approach is typically based on carbon–carbon cleavage triggered by ring-strain release and chelation assistance, and the products are also limited to a specific structural motif. Here we report a ligand-promoted β-carbon elimination strategy to activate the carbon–carbon bonds, which results in a range of transformations of aryl ketones, leading to useful aryl borates, and also to biaryls, aryl nitriles, and aryl alkenes. The use of a pyridine-oxazoline ligand is crucial for this catalytic transformation. A gram-scale borylation reaction of an aryl ketone via a simple one-pot operation is reported. The potential utility of this strategy is also demonstrated by the late-stage diversification of drug molecules probenecid, adapalene, and desoxyestrone, the fragrance tonalid as well as the natural product apocynin.     

Transformations of Aryl Ketones via Ligand‐Promoted C−C Bond Activation

The coupling of aromatic electrophiles (aryl halides, aryl ethers, aryl acids, aryl nitriles etc.) with nucleophiles is a core methodology for the synthesis of aryl compounds. Transformations of aryl ketones in an analogous manner via carbon–carbon bond activation could greatly expand the toolbox for the synthesis of aryl compounds due to the abundance of aryl ketones. An exploratory study of this approach is typically based on carbon–carbon cleavage triggered by ring‐strain release and chelation assistance, and the products are also limited to a specific structural motif. Here we report a ligand‐promoted β‐carbon elimination strategy to activate the carbon–carbon bonds, which results in a range of transformations of aryl ketones, leading to useful aryl borates, and also to biaryls, aryl nitriles, and aryl alkenes. The use of a pyridine‐oxazoline ligand is crucial for this catalytic transformation. A gram‐scale borylation reaction of an aryl ketone via a simple one‐pot operation is reported. The potential utility of this strategy is also demonstrated by the late‐stage diversification of drug molecules probenecid, adapalene, and desoxyestrone, the fragrance tonalid as well as the natural product apocynin.     

The first general palladium catalyst for the Suzuki-Miyaura and carbonyl enolate coupling of aryl arenesulfonates

The first general method for the palladium-catalyzed Suzuki-Miyaura and carbonyl enolate coupling of unactivated aryl arenesulfonates was developed utilizing XPhos, 1, and Pd(OAc)2. This is of significant interest because aryl tosylates and aryl benzenesulfonates are more easily handled and considerably less expensive than aryl triflates. This catalyst system effects the coupling of a variety of aryl, heteroaryl, and extremely hindered arylboronic acids with different aryl tosylates, under mild conditions. The same catalyst was employed in the first carbonyl enolate coupling of aryl arensulfonates.     

O,O-二烷基S-烷基(芳基)二硫代磷酸酯的异构化氯化反应——合成S-烷基S-烷基(芳基)二硫代磷酸衍生物的新方法

报道了合成S-烷基S-烷基(芳基)二硫代磷酸衍生物的一种便利的新方法。O,O-二烷基S-烷基(芳基)二硫代磷酸酯与三氯氧磷发生氯化反应的同时,伴随着P=S键异构成P-S键,生成S-烷基S-烷基(芳基)二硫代磷酰氯,在碱存在下进一步与各种亲核试剂反应,得到S-烷基S-烷基(芳基)二硫代磷酸衍生物。     

Palladium-catalyzed amination of aryl nonaflates

The first detailed study of the palladium-catalyzed amination of aryl nonaflates is reported. Use of ligands 2-4 and 6 allows for the catalytic amination of electron-rich and -neutral aryl nonaflates with both primary and secondary amines. With use of Xantphos 5, the catalytic amination of a variety of functionalized aryl nonaflates resulted in excellent yields of anilines; even 2-carboxymethyl aryl nonaflate is effectively coupled with a primary alkylamine. Moderate yields were obtained when coupling halo-aryl nonaflates with a variety of amines, where in most cases the aryl nonaflate reacted in preference to the aryl halide. Overall, aryl nonaflates are an effective alternative to triflates in palladium-catalyzed C-N bond-forming processes due to their increased stability under the reaction conditions.     

Efficient imidazolium salts for palladium-catalyzed Mizoroki-Heck and Suzuki-Miyaura cross-coupling reactions

The system, Pd(OAc)2/imidazolium salts (L2), was found as an efficient catalyst in the Heck coupling reaction of olefins with aryl halides and Suzuki reactions of various aryl halides with aryl boronic acids under aerobic condition. This catalytic system demonstrates great tolerance to a wide range of groups on all substrates of aryl halides, alkenes and aryl boronic acids.     

Valency changes of sulphur in the mass spectra of sulphones

The aryl substituent has been shown to affect the fragmentation and abundance of skeletal rearrangement ions in the spectra of aryl sulphonyl chlorides and sulphonic acids. The spectra of 2-hydroxy and 2-chloroethyl aryl sulphones contain [aryl SO]⁺ ions, suggesting that alkyl migration has competed successfully with aryl migration to the electron deficient oxygen atom.     

Highly efficient synthesis of phenols by copper-catalyzed hydroxylation of aryl iodides, bromides, and chlorides

8-Hydroxyquinolin-N-oxide was found to be a very efficient ligand for the copper-catalyzed hydroxylation of aryl iodides, aryl bromides, or aryl chlorides under mild reaction conditions. This methodology provides a direct transformation of aryl halides to phenols and to alkyl aryl ethers. The inexpensive catalytic system showed great functional group tolerance and excellent selectivity.     

Copper-mediated fluorination of aryl iodides

The synthesis of aryl fluorides has been studied intensively because of the importance of aryl fluorides in pharmaceuticals, agrochemicals, and materials. The stability, reactivity, and biological properties of aryl fluorides can be distinct from those of the corresponding arenes. Methods for the synthesis of aryl fluorides, however, are limited. We report the conversion of a diverse set of aryl iodides to the corresponding aryl fluorides. This reaction occurs with a cationic copper reagent and silver fluoride. Preliminary results suggest this reaction is enabled by a facile reductive elimination from a cationic arylcopper(III) fluoride.     

Inter- and Intramolecular Aryl–Aryl Interactions in Partially Fluorinated Ethylenedioxy-bridged Bisarenes**

Several ethylenedioxy-bridged bisarenes with a variety of type and number of aryl groups were synthesized to study non-covalent dispersion-driven inter- and intramolecular aryl–aryl interactions in the solid state and gas phase. Intramolecular interactions are preferably found in the gas phase. DFT calculations with and without dispersion correction show larger interacting aromatic groups increase the stabilization energy of folded conformers and decrease the intermolecular centroid–centroid distance. Single-molecule structures generally adopt folded conformations with short intramolecular aryl–aryl contacts. Gas electron diffraction experiments were performed exemplarily for 1-(pentafluorophenoxy)-2-(phenoxy)ethane. A new procedure for structure refinement was developed to deal with the conformational complexity of such molecules. The results are an experimental confirmation of the existence of folded conformations of this molecule with short intramolecular aryl–aryl distances in the gas phase. Solid-state structures are dominated by stretched structures without intramolecular aryl–aryl interactions but interactions with neighboring molecules.     

Palladium-catalyzed amination of aryl and heteroaryl tosylates at room temperature

Mild palladium-catalyzed aminations of aryl tosylates and the first aminations of heteroaryl tosylates are described. In the presence of the combination of L2Pd(0) (L = P(o-tol)3) and the hindered Josiphos ligand CyPF-t-Bu, a variety of primary alkylamines and arylamines react with both aryl and heteroaryl tosylates at room temperature to form the corresponding secondary arylamines in high yields with complete selectivity for the monoarylamine. These reactions at room temperature occur in many cases with catalyst loadings of 0.1 mol % and 0.01 mol % in one case, constituting the most efficient aminations of aryl tosylates by nearly 2 orders of magnitude. This catalyst is made practical by the development of a convenient method to synthesize the L2Pd(0) precursor. This complex is stable to air as a solid. In contrast to conventional relative rates for reactions of aryl sulfonates, the reactions of aryl tosylates are faster than parallel reactions of aryl triflates, and the reactions of aryl tosylates are faster than parallel or competitive reactions of aryl chlorides.     

Addition of aryl cuprates to azides: a novel approach for the synthesis of unsymmetrical diaryl amines

Aryl and benzyl azides react smoothly with aryl cuprates, generated in situ from aryl magnesium bromide and CuCN in THF to furnish a variety of unsymmetrical diaryl amines in good yields. This is the first report on the synthesis of diarylamines from aryl azides and aryl bromides via an organometallic approach.     

Tributyltin Aryl Selenides as Efficient Arylselenating Agents. Synthesis of Diaryl and Aryl Organyl Selenides

Tributyltin aryl selenides are highly efficient arylselenating agents in reactions with aryl iodides and aryl triflates under catalysis with Pd and Ni complexes respectively. They also may be used as efficient source of active arylselenolate anion in the presence of fluoride ions in reaction of arylselenation of alkyl halides and activated aryl fluorides.     

Rapid, easy cyanation of aryl bromides and chlorides using nickel salts in conjunction with microwave promotion

We report here a fast, easy, and efficient method for the preparation of aryl nitriles from aryl bromides and chlorides. The methodology for aryl bromides involves the use of either Ni(CN)(2) or NaCN and NiBr(2). With aryl chlorides, a mix of NaCN and NiBr(2) is used and the reaction proceeds via the in situ formation of the corresponding aryl bromide. The reaction can be performed in air and is complete within 10 min.     

Improved studies of cross‐coupling reactions of 5‐(tri‐n‐butystannyl)‐ and 5,5′‐bis(tri‐n‐butylstannyl)‐2,2′‐bithiophene with aryl halides

Stille coupling under standard conditions proceeds in low yield when using hindered organostannanes (1) or (2) and aryl bromide partners. The inclusion of aryl iodide instead of aryl bromide with the same organostannanes, significantly improves the efficiency of the coupling, providing a variety of desired products in good to excellent yield. The yields of Stille coupling are compared to the different reactivity of aryl halides. This study of Stille coupling with different aryl halides are documented and rationalized.     

Synthesis and photophysical properties of borondipyrromethene dyes bearing aryl substituents at the boron center

Several borondipyrromethene (Bodipy) dyes bearing an aryl nucleus linked directly to the boron center have been prepared under mild conditions. The choice of Grignard or lithio organo-metallic reagents allows the isolation of B(F)(aryl) or B(aryl)2 derivatives; where aryl refers to phenyl, anisyl, naphthyl, or pyrenyl fragments. A single crystal, X-ray structure determination for the bis-anisyl compound shows that the sp3 hybridized boron center remains pseudo-tetrahedral and that the B-C bond distances are 1.615 and 1.636 A. All compounds are electrode active but replacement of the fluorine atoms by aryl fragments renders the Bodipy unit more easily oxidized by 100 mV in the B(F)(aryl) and 180 mV in the B(aryl)2 compounds whereas reduction is made more difficult by a comparable amount. Strong fluorescence is observed from the Bodipy fluorophore present in each of the new dyes, with the radiative rate constant being independent of the nature of the aryl substituent. The fluorescence quantum yields are solvent dependent and, at least in some cases (aryl = anisyl or pyrenyl), nonradiative decay from the first-excited singlet state is strongly activated. There is no indication, however, for population of a charge-transfer state, in which the aryl substituent acts as donor and the Bodipy fragment functions as acceptor, that is strongly coupled to the ground state. Instead, it is conjectured that nonradiative decay involves a conformational change driven by the solvophobic effect. Thus, the rate of nonradiative decay in any given solvent increases with increasing surface accessibility (or molar volume) of the aryl substituent. Intramolecular energy transfer from pyrene or naphthalene residues to Bodipy is quantitative.     

Copper-mediated cross-coupling of aryl boronic acids and alkyl thiols

[reaction: see text] The cross-coupling of aryl boronic acids and alkanethiols mediated by copper(II) acetate and pyridine in anhydrous dimethylformamide affords aryl alkyl sulfides in good yield with a wide variety of substituted aryl boronic acids. The method is applicable to the synthesis of aryl sulfides of cysteine.     

Carbene adduct of cyclopalladated ferrocenylimine catalyzed α-arylation of ketones with aryl chlorides or bromides

Carbene adduct of cyclopalladated ferrocenylimine exhibited highly catalytic activity for the α-arylation of ketones with aryl halides. The corresponding products were obtained in moderate to excellent yields. Such protocol was applied to various ketones and a broad scope of aryl halides including aryl chlorides, bromides as well as unactivated and sterically hindered aryl halides.     

A general strategy for the perfluoroalkylation of arenes and arylbromides by using arylboronate esters and [(phen)CuR(F)

A versatile method for the synthesis of aryl perfluoroalkanes from arenes and aryl bromides is described. Substituted arenes or aryl bromides are converted in situ to an aryl boronate ester that readily undergoes perfluoroalkylation in air with [(phen)CuR(F)]. A broad range of aryl bromide substrates were perfluoroalkylated in good yield for the first time. [(phen)CuCF(3)] is now commercially available and has been prepared on 20?g scale.     

One-pot synthesis of acenaphtho[1,2-b]furan derivatives

New 9-(alkyl or aryl)acenaphtho[l,2-b]furan-8-(alky or aryl)amine compounds has herein been reported by one-pot reaction of (acenaphthylen-l-yloxy)trimethylsilane,alkyl and aryl aldehydes,and aryl and alky isocyanides in refluxing DMF.