Solid-supported acids for debenzylation of aryl benzyl ethers

Solid-supported acids have been investigated for aromatic debenzylation reactions. Stoichiometric amounts of solid-supported acids in refluxing toluene with or without 4 equiv of methanol effectively provided the desired aromatic debenzylation products of various systems in moderate to excellent yields (up to 98%).     

Highly Enantioselective Henry Reactions of Aromatic Aldehydes Catalyzed by an Amino Alcohol-Copper(II) Complex

Amino alcohol-Cu(II) catalyst: Highly enantioselective Henry reactions between aromatic aldehydes and nitromethane have been developed. The reactions were catalyzed by an easily available and operationally simple amino alcohol-copper(II) catalyst. In total, 38 substrates were tested and the R-configured products were obtained in good yields with excellent enantioselectivities.     

A mild and efficient method for nucleophilic aromatic fluorination using tetrabutylammonium fluoride as fluorinating reagent

<正>Anhydrous tetrabutylammonium fluoride(TBAF_(anh).) has been found to be a highly efficient fluorinating reagent for nucleophilic aromatic fluorinations such as fluorodenitration or halogen exchange(Halex) reaction.The products were formed in high to excellent yields under surprisingly mild reaction conditions and no phenol or ether side-products were detected in these reactions.     

Synthesis of aryl ketones or ketimines by palladium-catalyzed arene C-H addition to nitriles

The unprecedented palladium-catalyzed C-H addition of arenes to nitriles provides moderate to excellent yields of aryl ketones or the corresponding hindered imines. The addition of a small amount of DMSO increases the yields dramatically. Both intermolecular and intramolecular reactions are successful, although the intramolecular reactions tend to be more sluggish. This novel chemistry is believed to involve palladium-catalyzed C-H activation of the arene by electrophilic aromatic substitution, followed by the unusual carbopalladation of a nitrile. Similar reactions have been successfully developed employing arylboronic acids and nitriles. A concise route to xanthones starting from cheap starting materials has been developed employing this synthetic protocol.     

LiOH-Catalyzed Simple Ring Opening of Epoxides Under Solvent-Free Conditions

LiOH has been found to be a very simple and selective catalyst for the rapid and mild synthesis of β-hydroxy sulfides and β-hydroxyl nitriles by ring opening of epoxides with aromatic, aliphatic, and heterocyclic thiols and trimethylsilyl cyanide at room temperature under solvent free conditions. All the reactions proceeded satisfactorily in short times and afforded the corresponding products in good to excellent yields with high regioselectivity and chemoselectivity under mild reaction conditions.     

Efficient homo-coupling reactions of heterocyclic aromatic bromides catalyzed by Pd(OAc)2 using indium

Homo-coupling reactions of heterocyclic aromatic bromides smoothly proceeded with cat-Pd(OAc)₂, indium, and LiCl in DMF to afford exclusively symmetric biaryls possessing heterocyclic aromatic ring in good to excellent yields.     

House bulb light-induced photochemical acetalization of carbonyl compounds catalyzed by Eosin Y

We have systematically studied the reactions of acetalization and found that high reaction efficiency can be achieved using cheap and readily available organic Eosin Y as catalyst. The reaction proceeds smoothly under house bulbs and shows excellent functional group tolerance. The substrates of the reaction system are compatible with aromatic aldehydes, aliphatic aldehydes, aromatic ketones, and cyclic ketones with high yields.     

Pentamethylcyclopentadienide in organic synthesis: nucleophilic addition of lithium pentamethylcyclopentadienide to aromatic aldehydes and carbon-carbon bond cleavage of the adducts affording the parent aldehydes

Treatment of aromatic aldehyde with lithium pentamethylcyclopentadienide provided the corresponding carbinol in excellent yield. The carbinol returns to the parent aldehyde and pentamethylcyclopentadiene upon exposure to an acid or due to heating. The combination of the two reactions can represent a protection of aromatic aldehyde.     

Regioselective C−H Trifluoromethylation and Its Related Reactions of (Hetero)aromatic Compounds

Fluorinated functional groups, including trifluoromethyl group, play important roles in the development of drugs, agrochemicals, and organic functional materials. Therefore, the development of highly effective and practical reactions to introduce fluorinated functional groups into (hetero)aromatic compounds is highly desirable. We have achieved several regioselective C−H trifluoromethylation and related reactions by electrophilic and nucleophilic activation of six-membered heteroaromatic compounds and steric protection of aromatic compounds. These reactions proceed in good to excellent yields, even on a gram scale, with high functional group tolerance, and are applicable to the regioselective trifluoromethylation of drug molecules. In this personal account, the background of the introduction reactions of fluorinated functional groups, our reaction designs to achieve regioselective C−H trifluoromethylation and the related reactions of (hetero)aromatic compounds are explained.     

1,4‐Diazabicyclo[2.2.2]octane‐Catalyzed One‐Pot Synthesis of Pyrazolo[1,2‐a][1,2,4]triazole‐1,3‐diones under Ultrasound Acceleration

1,4‐Diazabicyclo[2.2.2]octane has been explored as an efficient catalyst to effect the three‐component condensation reactions between malononitrile, 4‐arylurazoles, and aromatic aldehydes in ethanol under ultrasound irradiation conditions. The reactions proceeded very rapidly under mild conditions to furnish the corresponding pyrazolo[1,2‐a][1,2,4]triazole‐1,3‐dione derivatives in excellent yields.     

Regioselective Aromatic Electrophilic Bromination with Dioxane Dibromide Under Solvent‐Free Conditions

Highly regioselective ring bromination of aromatic compounds has been accomplished with high yields and good purity using dioxane dibromide (DD) under solvent‐free conditions. Notable features of this methodology include operational simplicity, rapid reactions, excellent control over the degree of bromination, and tolerance of various functional groups during the reaction.     

Facile one-pot clean synthesis of benzimidazole motifs: Exploration on bismuth nitrate accelerated subtle catalysis

In the present letter, an efficient, clean and one-pot synthesis of 2-substituted benzimidazole and 1,2-disubstituted benzimidazole derivatives has been explored by reacting o-phenylenediamine with aromatic aldehydes using bismuth nitrate as a catalyst in ethanol at ambient temperature. This methodology avails with faster reactions, excellent yield, mild reaction conditions, use of inexpensive and non-toxic catalyst compared to literature reported hitherto.     

Aldol Reactions Catalyzed by Proline Functionalized Polyacrylonitrile Fiber

A proline functionalized fiber catalyst was employed for aldol reactions in water. In the presence of the fiber catalyst, the aldol reactions proceeded smoothly at 40℃ and the products were obtained in excellent yields which were higher than those obtained for the reactions catalyzed by L-proline or trans-4-hydroxy-L-proline. This newly developed fiber catalyst is applicable to the reactions of a wide range of aromatic aldehydes and exhibits excellent reusability(up to 6 times) without any additional treatment.     

Aggregation and reactivity in aqueous solutions of cationic surfactants and aromatic anions across concentration scales

The use of aqueous solutions as solvents in synthetic chemistry is one of the pathways towards more sustainable chemical processes. To increase solubility of reactants in aqueous solutions, surfactants can be used. In particular as a result of detailed kinetic studies involving probe reactions, our current understanding of the reaction environment offered by micelles is good to excellent. However, this understanding does not always translate well to reactions on a synthetic scale because concentrations are typically very different from concentrations used in probe reactions. These high concentrations may lead to changes in aggregate morphologies, in particular where aromatic anions are used in combination with cationic surfactants. An overview of aggregation processes and aggregate morphologies across concentration scales is presented together with a discussion of the resulting effects on reactivity in solutions containing cationic surfactants and (reactive) aromatic anions.     

水介质中无催化剂下醛酮与活泼亚甲基化合物的缩合反应

报道了水相中无催化剂下各种羰基化合物与活泼亚甲基化合物的Knoevenagel缩合反应. 芳香醛与活泼亚甲基化合物如丙二腈、氰基乙酸乙酯、氰基乙酰胺的缩合在室温下即能顺利进行, 获得了很高的收率; 而对于杂环芳醛、α,β-不饱和的醛以及脂肪醛与活泼亚甲基化合物的缩合, 需在50～65 ℃下进行, 也取得了很高的收率; 对于脂肪酮、芳香酮以及二元醛与丙二腈的缩合在75～85 ℃下也能顺利地进行, 获得中等以上的收率. 反应简单、高效而且对环境友好.     

Pseudo five-component process for the synthesis of functionalized tricarboxamides using CuI nanoparticles as reusable catalyst

An efficient and multicomponent method has been developed for the synthesis of functionalized tricarboxamides at room temperature using CuI nanoparticles as catalyst. This method involved fivecomponent coupling reactions of Meldrum's acid, isocyanides with aromatic aldehydes and amines at room temperature. Atom economy, wide range of products, excellent yields in short time and mild reaction conditions are some of the important features of this protocol. Notably, this catalyst could be recycled and reused for several times without significantly decreasing the catalytic activity.     

A novel substrate controlled chemoselective synthesis of aryl bis(thiazole-2-imine)methanes from 2-aminothiazoles and aldehydes

Aryl bis(thiazole-2-imine)methanes have been synthesized chemoselectively for the first time by an unusual reaction between 5-aryl substituted 2-aminothiazoles and aromatic aldehydes with excellent yield using inexpensive and easy available acetic acid as a catalyst under mild conditions. The present protocol was constructed through N-C bond formation by the condensation and nucleophilic addition reactions.     

Catalytic asymmetric ring opening of meso-epoxides with aromatic amines in water

[reaction: see text] An operationally simple and environmentally benign protocol for the catalytic asymmetric ring opening of meso-epoxides with aromatic amines has been developed. The reactions proceeded smoothly in the presence of 1 mol % of Sc(OSO3C12H25)3 and 1.2 mol % of a chiral bipyridine ligand in water to afford beta-amino alcohols in high yields with excellent enantioselectivities.     

An Efficient and General Procedure for the Cross-Coupling of Trimethylsilylacetylene and Vinylic,Aromatic or Heteroaromatic Bromides

Coupling reactions of trimethylsilylacetylene and vinylic, aromatic or heteroaromatic bromides can be carried out in very short time and with excellent yield using piperidine as a solvent and very small amounts of tetrakis(triphenylphosphine)palladium and copper(I)iodide (0.1 to 0.3 g on 100 mmol scale) as catalysts.     

Oxazoline‐Based Organocatalyst for Enantioselective Strecker Reactions: A Protocol for the Synthesis of Levamisole

A chiral oxazoline‐based organocatalyst has been found to efficiently catalyze asymmetric Strecker reactions of various aromatic and aliphatic N‐benzhydrylimines with trimethylsilyl cyanide (TMSCN) as a cyanide source at ?20 °C to give α‐aminonitriles in high yield (96 %) with excellent chiral induction (up to 98 % ee). DFT calculations have been performed to rationalize the enantioselective formation of the product with the organocatalyst in these reactions. The organocatalyst has been characterized by single‐crystal X‐ray diffraction analysis, as well as by other analytical methods. This protocol has been extended to the synthesis of the pharmaceutically important drug molecule levamisole in high yield and with high enantioselectivity.