An Efficient Synthesis of Thioesters Via TFA-Catalyzed Reaction of Carboxylic Acid and Thiols: Remarkably Facile C–S Bond Formation

Abstract

A general, facile, and efficient new synthetic path to thioesters was established by employing defined TFA-catalyzed reaction of carboxylic acid and thiol under mild conditions. The structure of the newly synthesized compounds was determined by infrared spectroscopy, nuclear magnetic resonance, and a single crystal X-ray crystallographic analysis.

Supplemental materials are available for this paper. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

C−S Cross-Coupling of Aryldiazonium Salts with Thiols Mediated by Gold

In this work, the coupling of aryldiazonium salts with thiols mediated by the readily accessible gold complex Me₂SAuCl is described. In the reported protocol, the addition of 2,2′-bipyridine as a ligand leads to higher yields than phosphines. The reaction proceeds at room temperature under soft mildconditions and has a broad scope in both the aryldiazonium salt and the thiol. Notably, the coupling works with aryldiazonium salts containing two additional substituents.     

Catalytic Activity of Polymetalorganosiloxanes Supported on Silica in the Metathesis of a C–Cl Bond

The catalytic activity of structurally different Cu- and Ni-containing polymetalorganosiloxanes supported on silica was studied using the reaction of C–Cl bond metathesis in the carbon tetrachloride–saturated hydrocarbon (n-decane) system as an example. Catalysts with low metal contents were found to exhibit the highest activity; an increase in the metal content resulted in a decrease in both conversion and specific activity. At the initial portions of kinetic curves, the reaction was described by first-order rate equations with respect to n-decane; the reaction was of fraction order with respect to CCl₄and catalyst. The activation energy of the process in the n-decane–carbon tetrachloride system on a copper-containing network catalyst was 23 ± 2 kcal/mol. The mechanism of catalysis on immobilized catalysts from the above class is discussed.     

Carbon–Carbon Bond Formation by Radical Cyclization: Regioselective Synthesis of Spiro Heterocyclic Compounds by n Bu3SnH‐Mediated Reaction

Several spiro heterocyclic compounds have been regioselectively synthesized in excellent yield by ⁿ Bu₃SnH‐AIBN‐mediated radical cyclization of 4‐(2′‐bromoaryloxymethyl)‐1‐methylquinolin‐2(1H)‐ones in refluxing benzene under nitrogen for 4 h.     

C‐C Bond Formation by Radical Cyclization: Regioselective Synthesis of [6,6] Pyrano pyran System

Abstract

Abstract:?A number of 4‐aryloxymethyl pyrano[3,2‐c][1]benzopyran‐5‐(2H)‐ones 3(a–f) were prepared by refluxing 4‐chloromethyl pyrano[3,2‐c][1]benzopyran‐5‐(2H)‐ones 1(a,b) with o‐bromophenols 2(a–c) in acetone in the presence of anhydrous potassium carbonate and sodium iodide in 70–80% yield. Compounds 3(a–f) were then subjected to radical cyclization by refluxing with tri‐n‐butyltin chloride, sodium cyanoborohydride, and azobisisobutyronitrile (AIBN) in dry benzene for 4–5 h to give a cis‐diastereomeric mixture of [6,6]pyranopyran derivatives in 80–85% yield.     

Electrochemical Synthesis of Thienoacene Derivatives: Transition-Metal-Free Dehydrogenative C−S Coupling Promoted by a Halogen Mediator

The first electrochemical dehydrogenative C−S bond formation leading to thienoacene derivatives is described. Several thienoacene derivatives were synthesized by dehydrogenative C−H/S−H coupling. The addition of ⁿBu₄NBr, which catalytically promoted the reaction as a halogen mediator, was essential.     

Transition-Metal-Free Aryl–Aryl Cross-Coupling: C−H Arylation of 2-Naphthols with Diaryliodonium Salts

Transition-metal-free regioselecitive C−H arylation of 2-naphthols with diaryliodonium salts has been developed. The reaction proceeds under very simple experimental conditions and affords a range of products with various substitution patterns. The method allows for the incorporation of electron-deficient aryls, which complements well currently existing metal-free aryl–aryl cross-couplings of phenols that have been so far restricted to the introduction of electron-rich aryl moieties. The mechanism of the reaction was studied by means of DFT calculations, demonstrating that the C−C bond formation occurs via a dearomatization of 2-naphthol substrate, followed by a subsequent rearomatization by tautomerization. The computations show that the use of a low polarity solvent and an insoluble inorganic base is key to securing the high selectivity of the C−C coupling over a competing C−O arylation pathway, by preventing the incipient deprotonation of 2-naphthol.     

p-Toluene Sulfonic Acid–Catalyzed,Solvent-Free Synthesis of Symmetrical Bisamides by Reaction Between Aldehydes and Amides

Reaction between aldehydes and amides catalyzed by p-toluene sulfonic acid in solvent-free conditions provided a simple and efficient one-pot route for the synthesis of symmetrical bisamide derivatives in excellent yields.     

Air-Stable,Cationic, Lewis Acid,Titanocene Perfluorooctanesulfonate–Catalyzed Reductive Cleavage of S–S Bond by Zinc and Its Application in Synthesis of Thioesters

Titanocene perfluorooctanesulfonate is air-stable complex. In the presence of 10 mol% of the complex, reductive cleavage of an S–S bond by zinc in commercial tetrahydrofuran at room temperature led to nucleophilic sulfur anion species, which reacted with acid anhydrides to afford thioesters in good to excellent yields.     

Silica Supported Perchloric Acid:A Convenient and Environmentally Friendly Catalyst for the One-pot Multicomponent Synthesis of β-Acetamido Ketones

A modified Dakin‐West one‐pot, four‐component condensation of an aryl aldehyde, aryl ketone, acetyl chloride and acetonitrile in the presence of silica supported perchloric acid as an active, inexpensive, recoverable and recyclable catalyst is reported for the synthesis of β‐acetamido ketones under mechanical stirring and ultrasonic irradiation conditions. This system has advantages of short reaction times, good to excellent yields and the ability to carry out the large scale reactions. The use of ultrasound increases the rate of reactions compared with reactions at reflux conditions.     

C–C Bond Rupture in the Oxidation of Lower (C2–C6) Alcohols with Hydrogen Peroxide Mediated by Iron-Containing Compounds

C–C bond rupture upon the oxidation of alcohols in the Fe(ClO₄)₃+ H₂O₂system in aqueous acetonitrile at room temperature is found. The relative yield of the products of C–C bond rupture is 20–30% under standard conditions for C₂and C₃alcohols and decreases in the series C₂> C₃> C₄> C₆. The alkyl radical and carboxylic acid are the products of C–C bond rupture in alcohol oxidation. Cyclohexane is a competitive inhibiting agent for C–H bond oxidation in 1-propanol, and it does not affect the yield of the products of C–C bond rupture. When H₂O₂is replaced by tert-BuOOH, the fraction of the products of C–C bond rupture decreases by an order of magnitude. Our data suggest that a non-radical intermediate, likely Fe(III) hydroperoxo complex, is responsible for C–C bond rupture in alcohol under the reaction conditions.     

Plasma-Assisted Coupling Reactions of Dinitrogen and Carbon Dioxide Mediated by Monometallic YB1–4−⋅Anions: Carbon−Nitrogen Bond Formation

Transition-metal catalyzed coupling to form C−N bonds is significant in chemical science. However, the inert nature of N₂ and CO₂ renders their coupling quite challenging. Herein, we report the activation of dinitrogen in the mild plasma atmosphere by the gas-phase monometallic YB_1–4⁻ anions and further coupling of CO₂ to form C−N bonds by using mass spectrometry and theoretical calculation. The observed product anions are NCNBO⁻ and N(BO)₂⁻, accompanied by the formation of neutral products YO and YB_0–2NC, respectively. We can tune the reactivity and the type of products by manipulating the number of B atoms. The B atoms in YB_1–4N₂⁻ act as electron donors in CO₂ reduction reactions, and the carbon atom originating from CO₂ serves as an electron reservoir. This is the first example of gas-phase monometallic anions, which are capable to realize the functionalization of N₂ with CO₂ through C−N bond formation and N−N and C−O bond cleavage.     

Zinc-Mediated Tandem-One-Pot Facile Synthesis of 1-(Arylsulfonyl) Aryl/Heteryl Methanes: A Case of C‒S Bond Formation

Reaction of arylmethyl/heteryl methyl zinc chloride (generated in situ from aryl methyl and heteryl methyl chloride and zinc metal) with aryl sulfonyl chlorides in tetrahydrofuran (THF) under mild conditions (i.e., at room temperature) furnishes the corresponding 1-(aryl sulfonyl)aryl/heteryl methanes in good yields.

C–O,C–S,C–N,and C–C Bond Formation at the Periphery of the Macrocycle during Chemical Modification of Phytochlorins: Key Methods and Synthetic Applications

Russian Journal of General Chemistry - The main methods of C-O, C-S, C-N, and C-C bond formation at the periphery of the macocrocycle during chemical modification of phytochlorins in the synthesis...     

Understanding the C−F Bond Activation Mediated by Frustrated Lewis Pairs: Crucial Role of Non-covalent Interactions

The activation of a single C−F bond in di- and trifluoromethyl groups by frustrated Lewis pairs (FLPs) has been computationally explored by means of Density Functional Theory calculations. It is found that in this activation reaction the FLP partners exhibit a peculiar cooperative action, which is markedly different from related FLP-mediated processes, and where non-covalent interactions established between the Lewis base and the substrate play a decisive role. In addition, the process proceeds through the intermediacy of a hypervalent species featuring a pentacoordinate carbon atom, which is rare in the chemistry of FLPs. The physical factors controlling this process as well as the bonding situation of these hypervalent intermediates have been quantitatively analyzed in detail by using state-of-the-art computational methods to not only rationalize the mechanism of the transformation but also to guide experimentalists towards the realization of these so far elusive hypervalent systems.     

Sulfonic Acid–Functionalized Silica (SiO2-Pr-SO3H) as a Solid and a Heterogeneous Catalyst in Green Organic Synthesis: Recent Advances

The application of sulfonic acid–functionalized silica (SBA-Pr-SO₃H) as a catalyst in organic synthesis has become an efficient and green strategy for the selective construction of organic motifs. Therefore, the great efforts have been made by scientists to replace the conventional acid catalysts by sulfonic acid–functionalized silica used as solid, heterogeneous catalyst in various organic transformations. The sustainable advantage of sulfonic acid–functionalized silica is that it can be recovered and reused several times without loss of its efficiency. In this tutorial review, we attempt to give an overview about the use of sulfonic acid–functionalized silica as a catalyst in the synthesis of various organic compounds having industrial as well as pharmaceutical applications.     

Reductive Coupling of (Fluoro)pyridines by Linear 3d-Metal(I) Silylamides of Cr–Co: A Tale of C−C Bond Formation,C−F Bond Cleavage and a Pyridyl Radical Anion

Herein, we disclose the facile reduction of pyridine (and its derivatives) by linear 3d-metal(I) silylamides (M=Cr–Co). This reaction resulted in intermolecular C−C coupling to give dinuclear metal(II) complexes bearing a bridging 4,4′-dihydrobipyridyl ligand. For iron, we demonstrated that the C−C coupling is reversible in solution, either directly or by reaction with substrates, via a presumed monomeric metal(II) complex bearing a pyridyl radical anion. In the course of this investigation, we also observed that the dinuclear metal(II) complex incorporating iron facilitated the isomerisation of 1,4-cyclohexadiene to 1,3-cyclohexadiene as well as equimolar amounts of benzene and cyclohexene. Furthermore, we synthesised and structurally characterised a non-3d-metal-bound pyridyl radical anion. The reactions of the silylamides with perfluoropyridine led to C−F bond cleavage with the formation of metal(II) fluoride complexes of manganese, iron and cobalt along with the homocoupling or reductive degradation of the substrate. In the case of cobalt, the use of lesser fluorinated pyridines led to C−F bond cleavage but no homocoupling. Overall, in this paper we provide insights into the multifaceted behaviour of simple (fluoro)pyridines in the presence of moderately to highly reducing metal complexes.     

Synthesis of 1,3-benzothiazines by intramolecular dehydrogenative C–S cross-coupling in a flow electrolysis cell

Dehydrogenative cyclization of thioamides is an attractive approach for the synthesis of S-heterocycles. Reported herein is an electrochemical dehydrogenative cyclization reaction of N-benzyl thioamides in a flow electrolysis cell. The continuous-flow electrosynthesis has addressed the limitations associated with previously reported methods for the cyclization of alkylthioamides and provide a transition metal-and oxidizing reagent-free access to various functionalized 1,3-benzothiazines in good yields.