Synthesis of ynones by palladium-catalyzed acylation of terminal alkynes with acid chlorides

Phosphane-free oxime-derived palladacycle 2 is an efficient precatalyst for the copper-free acylation of terminal alkynes with different carboxylic acid chlorides in toluene in the presence of 3 equiv of TEA as base, giving the corresponding ynones in good yields. The coupling reaction can normally be performed under air or under inert atmosphere when very low catalyst loadings (10(-3) mol % Pd) (turnover numbers (TONs) up to 23,000, turnover frequencies (TOFs) up to 958 h(-1)) or sensitive carboxylic acid chlorides are used. In addition, Pd(OAc)(2) has been shown as an efficient catalyst for the ligandless process, although usually working under higher loading conditions. This new protocol allows one to perform the synthesis of ynones at 110 degrees C, at room temperature, or under microwave irradiation conditions.     

Glyoxylic acid as catalyst： A simple selective synthesis of 1,2-disubstituted benzimidazoles in aqueous media

Glyoxylic acid （5 mol%） performs as a novel highly water-soluble catalyst for the synthesis of 2-aryl-l-arylmethyl-lH- benzimidazoles from a wide range of substituted o-phenylenediamines and various substituted aldehydes in good to excellent isolated yields （85-95%） using water as solvent at ambient temperature. The remarkable advantages offered by this method are easily and inexpensive available catalyst, simple procedure, mild conditions, much faster （20--40 rain） reactions and excellent yields of products.     

Novel,efficient,and green procedure for the synthesis of 1,5-benzodiazepines catalyzed by MgBr_2 in aqueous media

MgBr_2 performs as a novel catalyst for the synthesis of various 1,5-benzodiazepine derivatives from wide range of substituted ophenylenediamines and various ketones in good to excellent isolated yields(93-98%)using water as solvent at ambient temperature.Several solvents were examined for this reaction;however,in terms of reaction yield and time,water was found to be the optimum solvent.The remarkable advantages offered by this method are easily and inexpensive available catalyst,simple procedure,mild c...     

Silica-supported zinc bromide (ZnBr2/SiO2): a highly efficient heterogeneous catalyst for coupling acid chlorides with terminal alkynes

Silica-supported zinc bromide (ZnBr₂/SiO₂) is an efficient heterogeneous catalyst for the rapid synthesis of ynones by cross-coupling of acid chlorides with terminal alkynes in good to excellent yields under solvent-free conditions at room temperature.     

Enantioselective Synthesis of Tertiary Propargylic Alcohols under N‐Heterocyclic Carbene Catalysis

A straightforward procedure to carry out the enantioselective benzoin reaction between aldehydes and ynones by employing a chiral N‐heterocyclic carbene (NHC) as catalyst was developed. Under the optimized reaction conditions, these ynones undergo a clean and selective 1,2‐addition with the catalytically generated Breslow intermediate, not observing any byproduct arising from competitive Stetter‐type reactivity. This procedure allows the preparation of tertiary alkynyl carbinols as highly enantioenriched materials, which have the remarkable potential to be used as chiral building blocks in organic synthesis.     

Zn-proline catalyzed selective synthesis of 1,2-disubstituted benzimidazoles in water

Zn-proline (5 mol%) performs as a novel water-soluble and recyclable Lewis acid catalyst for the selective synthesis of 1,2-disubstituted benzimidazoles from wide range of substituted o-phenylenediamines and aldehydes in moderate to excellent isolated yields (42-92%) using water as solvent at ambient temperature.     

1,3‐O‐Transposition or Trisubstituted Z‐Enol Ester? A Comparative Study of Reactions of Ynones

Ynones are useful substrates for transition‐metal‐mediated synthesis. The Au^I‐catalyzed 1,3‐O‐transposition is an important reaction of ynones. Recently, an efficient Cu^I‐catalyzed synthesis of trisubstituted Z‐enol esters via interrupting the traditional 1,3‐O‐transposition reaction of ynones was reported by Zhu's group. Herein, density functional theory studies disclosed that the hydrogen bond formed by carboxylic acid plays an important role for the reactivity and selectivity in this novel reaction. A qualitative rule was also found to explain the substituent effect in the ynone substrate, and this is consistent with experiments. The Au^I‐catalyst and Cu^I‐catalyst were further compared to interpret the essential cause of why the Au^I‐catalyst prefers the 1,3‐O‐transpostion reaction. These conclusions might be helpful for the rational design of reactions of ynones.     

Facile and efficient addition of terminal alkynes to benzotriazole esters: synthesis of d-erythro-sphingosine using ynones as the key intermediate

From the perspective of synthesis, ynones are compounds of considerable interest because of their occurrence in a wide variety of biologically active molecules and as key synthetic intermediates. In this context, a facile and highly efficient synthesis of ynones was developed based on the high reactivity of benzotriazole esters formed in situ. Lithium acetylides can alkylate various carboxylic acids in yields ranging from 60% to 92%. To determine whether our methodology is useful for synthesising complex and biologically relevant molecules, we synthesise d-erythro-sphingosine in four steps and with 33% overall yield from l-serine.     

Solvent free synthesis of ynones using magnetically recoverable Copper-ferrite nanoparticles

A general and efficient biogenic CuFe₂O₄ MNP’s catalyzed synthesis of ynones has been reported for the first time. The reaction occurs in solvent free conditions without the use of any harsh conditions. The average diameter of the nanoparticles was found to be 13.07 nm. The advantages of the protocol include heterogeneous catalysis, easy recyclability of the catalyst and short reaction time.     

Ga(ClO4)3-catalyzed Reaction of 1,2-Diamines and α-Bromoketones: Synthesis of 2-Substituted Quinoxalines

Ga(ClO₄)₃-catalyzed reaction of 1,2-aryldiamines and α-bromoketones to afford 2-substituted quinoxa- lines in good yields is described. The reaction proceeded via grinding process with 10%(molar fraction) catalyst under solvent-free conditions at room temperature. For unsymmetrical o-phenylenediamines bearing electron-with- drawing groups, regio-selective quinoxalines were obtained.     

Tributylphosphine catalyzed addition of diphenylphosphine oxide to unsubstituted and substituted electron-deficient alkenes

The PBu₃-catalyzed conjugate addition of diphenylphosphine oxide to unsubstituted and substituted electron-deficient alkenes is reported. β-Substituted α,β-unsaturated esters, trans-methyl crotonate and trans-methyl cinnamate, known for their reluctance to participate in phosphine-catalyzed transformations, also react well under the developed conditions. Mild reaction conditions, simple work-up and the ease of catalyst recovery make the proposed methodology useful for the preparation of functionalized tertiary phosphine oxides. The utility of this method was demonstrated by the gram-scale reactions of diphenylphosphine oxide with electron-deficient alkenes.     

Graphene oxide: A carbocatalyst for the one-pot multicomponent synthesis of highly functionalized tetrahydropyridines

A simple, straightforward and efficient methodology is described for the synthesis of polysubstituted tetrahydropyridine via one-pot multicomponent reaction of β-ketoester, aldehyde and aniline in presence of catalytic amount of graphene oxide in acetonitrile. Graphene oxide is a versatile carbocatalyst and this is the first report on its application in a five component reaction. Good yield, usage of readily available starting material, operational simplicity, easy work-up and eco-friendly re-usable catalyst are the key features of this protocol.     

Sulfonated graphene oxide as highly efficient catalyst for glycosylation

Heterogeneous sulfonated graphene oxide for the first time has been used as a green and efficient catalyst for atom-economic glycosylation of unprotected, unactivated glycosyl donors or 2,3,4,6-tetra-O-acetylglycosyltrichloroacetimidate with various acceptors basically in the absence of solvent. The unprotected, unactivated glycosyl donors afforded mixtures of α- and β-glycosides, while the 2,3,4,6-tetra-O-acetylglycosyltrichloroacetimidate afforded β-glycosylated products with high yields and selectivity. The main advantages of this methodology are easy catalyst preparation, no need for dry reagents and reaction conditions, easy catalyst separation and recycling, and high product yields.     

Using Pd-salen complex as an efficient catalyst for the copper-and solvent-free coupling of acyl chlorides with terminal alkynes under aerobic conditions

<正>The palladium-salen complex palladium(Ⅱ) N,N'-bis{[5-(triphenylphosphonium)-methyl]salicylidene}-1,2-ethanediamine chloride was found to be a highly active catalyst for the copper- and solvent-free coupling reaction of terminal alkynes with different acyl chlorides in the presence of triethylamine as base,giving excellent ynones under aerobic conditions.     

Efficient synthesis of 2,3-dihydroquinazolin-4(1H)-ones catalyzed by titanium silicon oxide nanopowder in aqueous media

An efficient synthesis of 2,3-dihydroquinazolin-4(1H)-one derivatives is accomplished in aqueous media by a three-component reaction of isatoic anhydride, primary amines or ammonium acetate, and aldehydes catalyzed by titanium silicon oxide nanopowder. A variety of 2,3-dihydroquinazolin-4(1H)-one derivatives were synthesized using this methodology in good to excellent yields. The catalyst was recovered and recycled up to four times without significant loss in the catalytic activity.     

Graphene oxide (GO)-catalyzed chemoselective thioacetalization of aldehydes under solvent-free conditions

An efficient method for the synthesis of open chain, cyclic, and unsymmetrical dithioacetals from aryl/hetero-aryl/aliphatic aldehydes is described. The reaction is performed using graphene oxide (GO) as the catalyst under solvent-free and aerobic conditions. High chemoselectivity is observed in the reaction as aryl/alkyl ketones do not give thioketals under the condition.     

Iron oxide and alumina nanocomposites applied to Fischer-Tropsch synthesis

Nanocomposites composed of nanoparticles of iron oxide and aluminium oxide (Fe(2)O(3)-Al(2)O(3)) with a unique structure show a remarkable catalytic performance in Fischer-Tropsch synthesis (FTS), compared with the traditional iron-based catalyst.     

An efficient synthesis of 1,5-benzodiazepine derivatives catalyzed by boric acid

1,5-Benzodiazepine derivatives have been synthesized by the condensation of o-phenylenediamines and ketones in the presence of boric acid as catalyst under mild conditions.This method is simple,environmentally benign and high yielding.     

Highly efficient transition metal-free coupling of acid chlorides with terminal alkynes in [bmim]Br: A rapid route to access ynones using MgCl2

A simple, mild, highly efficient and transition metal-free protocol for synthesis of ynones in an ionic liquid is described. In this approach, the coupling reaction of different acid chlorides with terminal alkynes was efficiently carried out using 0.05 mol% MgCl₂ in the presence of triethylamine in [bmim]Br at room temperature to afford the corresponding ynones in good to excellent yields. This method is highly efficient for various acid chlorides and alkynes including aliphatic, aromatic, and heteroaromatic substrates bearing different functional groups. The influence of some parameters in this reaction including type of ionic liquid, base and catalyst has been discussed.     

Styrene synthesis over iron oxide catalysts: from single crystal model system to real catalysts

Surface science methods originating from analysis of noble metal catalysts are increasingly applied to metal oxides. These methods provide direct access to fundamental structural properties and phase equilibria governing the catalytic properties of metal oxide surfaces. However, no systematic way existed so far for transferring this knowledge to technical catalysts. The aim of this paper is to combine surface science with chemical engineering methods to bridge this gap. Styrene synthesis over pure and K-doped iron oxides is used as an example to develop and to explain the methodology. Single crystal films (SCF), grown epitaxially on a Pt-carrier are considered as ideal model surfaces. Comprehensive UHV analyses yield the structural properties of SCF as well as their interaction with relevant components of the reaction mixture. Their results are combined with conversion experiments to derive a mechanistic catalyst model along with quantitative information on the reaction rates. The activity of SCF as well as their phase transitions under reactive conditions can be described with a continuum model depending on the macroscopic properties of the system. This model forms the crucial link towards technical catalysts. It is shown that the behaviour of a powder catalyst can be described as a superposition of the above kinetic model and an appropriate porous model. In this paper we review the developed methodology and conclude with the evaluation of the concept.