Bismuth triflate-catalyzed mild and efficient epoxide opening by aromatic amines under aqueous conditions

Bismuth triflate catalyzes the ring opening of epoxides with aromatic amines under aqueous conditions. The reaction proceeds rapidly and affords the corresponding β-amino alcohols in excellent yields.     

Scope and limitations of montmorillonite K 10 catalysed opening of epoxide rings by amines

Montmorillonite K 10 efficiently catalyses the opening of epoxide rings by amines in high yields with excellent regio- and diastereo-selectivities under solvent-free conditions at room temperature affording an improved process for synthesis of 2-amino alcohols. Reaction of cyclohexene oxide with aryl/alkyl amines leads to the formation of trans-2-aryl/alkylaminocyclohexanols. For unsymmetrical epoxides, the regioselectivity is controlled by the electronic and steric factors associated with the epoxide and the amine. Selective nucleophilic attack at the benzylic carbon of styrene oxide takes place with aromatic amines, whereas, aliphatic amines exhibit preferential nucleophilic attack at the terminal carbon. Aniline reacts selectively at the less hindered carbon of other unsymmetrical epoxides. The difference in the internal strain energy of the epoxide ring in cycloalkene oxides and alkene oxides led to selective nucleophilic opening of cyclohexene oxide by aniline in the presence of styrene oxide. Due to the chelation effect, selective activation of the epoxide ring in 3-phenoxy propylene oxide takes place in the presence of styrene oxide leading to preferential cleavage of the epoxide ring in 3-phenoxy propylene oxide by aniline.     

Efficient ring opening of epoxides with trimethylsilyl azide and cyanide catalyzed by erbium(III) triflate

Epoxides can be opened under neutral conditions with TMSN₃ and TMSCN in the presence of catalytic amounts of Lewis acid, affording the corresponding ring-opened compounds in high yields.     

Effect of a carboxyl group on the chemiluminescent reaction of tris(2,2′-bipyridine)ruthenium(III) with aliphatic amines

The effect of a carboxyl group beside nitrogen of aliphatic amines on the tris(2,2′-bipyridine)ruthenium(III), Ru(bpy)₃³⁺, chemiluminescent reaction was examined. It has been shown that a carboxylate anion promotes the chemiluminescent reaction at a lower pH and then the aliphatic amines with this substituent can be sensitively detected compared with corresponding aliphatic amines without this substituent. Based on this finding, preliminary studies on simultaneous determination of 4-hydroxyproline, N-methylglycine, N-methylalanine, proline, and pipecolic acid in human serum have been performed using isocratic reversed-phase ion-pair high-performance liquid chromatography (HPLC) with electrogenerated Ru(bpy)₃³⁺ chemiluminescent detection. The detection limits (signal-to-noise ratio of 3) with the proposed method were 3.0, 12, 2.7, 4.6, and 10 nM for 4-hydroxyproline, N-methylglycine, N-methylalanine, proline, and pipecolic acid, respectively.     

Kinetics and mechanism of oxidation of some aliphatic amines by ditelluratocuprate(III)

The kinetics of oxidation of some primary, secondary and tertiary aliphatic amines by ditelluratocuprate(III) was studied in alkaline medium. The order in both substrate and oxidant was found to be unity each. The reaction rate decreased with increase in ionic strength. The order of reactivity of amines was found to be secondary > primary > tertiary. A mechanism was proposed involving an adduct formation between amine and monotelluratocuprate(III), which dissociates further in a slow step followed by fast steps to give required products. TheTaft linear free energy relationship was shown to be applicable which also supports the proposed mechanism.

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Kinetik und Mechanismus der Oxidation einiger aliphatischer Amine mit Kupfer(III)-ditellurat

Zusammenfassung Die Kinetik der Oxidation einiger primärer, sekundärer und tertiärer aliphatischer Amine mit Kupfer(III)-ditellurat wurde in alkalischem Medium untersucht. Die Reaktion war jeweils erster Ordnung bezüglich Substrat und Oxidationsmittel. Die Reaktionsgeschwindigkeit nahm mit zunehmender Ionenstärke ab. Die Reaktivität stieg in der Reihenfolge sekundäre > primäre > tertiäre Amine an. Ein Mechanismus, der die Bildung eines Adduktes zwischen Amin und Kupfer(III)-monotellurat beinhaltet, wird vorgeschlagen. Dieses Addukt dissoziiert in einem langsamen Schritt, gefolgt von schnellen Schritten, in denen die gefundenen Produkte gebildet werden. Die Anwendbarkeit derTaft-Beziehung wurde getestet und unterstützt den vorgeschlagenen Mechanismus.

     

Highly efficient and versatile chemoselective addition of amines to epoxides in water catalyzed by erbium(III) triflate

Er(OTf)₃ is proposed as a highly efficient and reusable catalyst for the opening of epoxides in water with aliphatic as well as aromatic amines leading to the synthesis of β-amino alcohols. The aqueous conditions employed in the present method will make it ‘environmentally friendly’ and potentially useful for industrial applications.     

Bismuth triflate-catalyzed oxa- and thia-Pictet-Spengler reactions: access to iso- and isothio-chroman compounds

A new route to functionalized iso(thio)chromans is described. The compounds are accessible easily in a one pot-reaction by using different benzaldehydes and phenylethanethiol or phenylethanol in presence of bismuth triflate.     

Highly efficient ring opening reactions of epoxides with deactivated aromatic amines catalyzed by heteropoly acids in water

Heteropoly acid was found to be an effective and efficient catalyst for the ring opening reaction of epoxides with various aromatic amines to produce the corresponding β-amino alcohols in moderate to excellent yields in water. This method provides a new and efficient protocol in terms of mild reaction conditions, clean reaction profiles, small quantity of catalyst, and simple work-up procedure.     

Synthesis of heteroarylated ketones via bismuth(III) triflate-promoted regioselective 1,4- and 1,6-additions of electron-rich heteroarenes to cyclic enones and dienones

The development and optimization of bismuth(III) triflate-promoted regioselective 1,4- and 1,6-additions of electron-rich heteroarenes to cyclic, β,β-disubstituted enones and dienones is described. Additions of a range of heteroarenes, including furan, thiophene, pyrrole, and indole nucleophiles, to cyclic, β,β-disubstituted enones occur to form all-carbon quaternary centers in up to 88% yield. In addition, regioselective 1,6-additions of electron-rich heteroarenes to 3-vinyl-2-cyclohexenone occur to produce a variety of δ-heteroarylated, β,β-disubstituted enones in up to 93% yield. The high 1,6-selectivity for these reactions is attributed to the increased steric bulk at the β-position relative to the δ-position, and no competing 1,4-conjugate addition is observed.     

Spectroscopic study on the complex formation of chromogenic bridged calixarenes with aliphatic amines

The complex formation between chromogenic capped calix 4 arene derivatives comprising indophenol indicator group(s), and aliphatic amines has been studied by UV/Vis spectroscopy. The equilibrium constants have been determined in ethanol, and—for one ligand—also in dimethylsulfoxide. The results have been interpreted in terms of various types of host–guest interactions and of steric effects.     

Three components synthesis of homoallylic amines catalyzed by bismuth(III) nitrate pentahydrate

Bismuth (III) nitrate pentahydrate catalyzes efficiently the three-component condensation of aldehydes, amines, and allyltributylstannane at rt to afford the corresponding homoallylic amines in excellent yield.     

Aluminum(III) triflate-catalyzed selective oxidation of glycerol to formic acid with hydrogen peroxide

Glycerol is a by-product of biodiesel production and is an important readily available platform chemical. Valorization of glycerol into value-added chemicals has gained immense attention. Herein, we carried out the conversion of glycerol to formic acid and glycolic acid using H₂O₂ as an oxidant and metal (III) triflate-based catalytic systems. Aluminum(III) triflate was found to be the most efficient catalyst for the selective oxidation of glycerol to formic acid. A correlation between the catalytic activity of the metal cations and their hydrolysis constants (K_h) and water exchange rate constants was observed. At 70 °C, a formic acid yield of up to 72% could be attained within 12 h. The catalyst could be recycled at least five times with a high conversion rate, and hence can also be used for the selective oxidation of other biomass platform molecules. Reaction kinetics and ¹H NMR studies showed that the oxidation of glycerol (to formic acid) involved glycerol hydrolysis pathways with glyceric acid and glycolic acid as the main intermediate products. Both the [Al(OH)_x]ⁿ⁺ Lewis acid species and CF₃SO₃H Brønsted acid, which were generated by the in-situ hydrolysis of Al(OTf)₃, were responsible for glycerol conversion. The easy availability, high efficiency, and good recyclability of Al(OTf)₃ render it suitable for the selective oxidation of glycerol to high value-added products.     

Investigation of copper(II) tetrafluoroborate catalysed epoxide opening

We report the extension of the copper(II) tetrafluoroborate catalysed opening of epoxides with alcohols to include a wider variety of alcohols, a range of solvents and a method to purify the products from the reaction.     

Efficient and practical catalytic vinylogous aldol reaction of dioxinone-derived silyl dienol ethers with aromatic aldehydes

Vinylogous Mukaiyama-aldol reaction was realized by use of dioxinone-derived silyl dienol ethers and various aldehydes in the presence of highly catalytic amounts of bismuth triflate. The reaction proceeds rapidly and affords the corresponding β-hydroxy-1,3-dioxin-4-ones in very good to excellent yields (up to 98%).     

Direct-type catalytic three-component Mannich reaction in aqueous media

Bismuth triflate catalyzed direct-type Mannich reaction of cyclohexanone, aromatic aldehyde, and aromatic amine proceeded smoothly in water to afford the corresponding β-amino ketone with very good yield and moderate to good anti selectivity.     

Bismuth triflate catalyzed Claisen rearrangement of allyl naphthyl ethers

Bismuth triflate was found to be an efficient catalyst for the Claisen rearrangement of allyl naphthyl ethers. The reaction proceeds smoothly with a catalytic amount of bismuth triflate (20 mol %) to afford the corresponding ortho-allyl naphthol in moderate to good yields in most cases.     

Direct reductive amination using triethylsilane and catalytic bismuth(III) chloride

Direct reductive amination (DRA) using triethylsilane (TESH) and catalytic bismuth(III) chloride (BiCl₃) is described for the first time. The use of TESH and BiCl₃ provides easy handling, low cost, non-toxicity, and a mild Lewis acid activity, thereby meeting the demand for green and sustainable chemistry. The developed DRA is highly chemoselective and applicable to less-basic amines. The experimental results of this study revealed that the developed DRA could be catalyzed by BiCl₃, which was gradually reduced to Bi(0) or bismuth with a low valency by TESH, but TESCl, Bi(0), and Bi(0) with TESCl catalyzed the DRA to some extent.     

One-pot solvent-free synthesis of triaryl- and triheteroarylmethanes by Bi(OTf)3-catalyzed Friedel-Crafts reaction of arenes/heteroarenes with trialkyl orthoformates

A convenient, practical and highly efficient one-pot method has been developed for the synthesis of triaryl- and triheteroarylmethane derivatives by Bi(OTf)₃-catalyzed Friedel-Crafts alkylation of trialkyl orthoformates in combination with a wide variety of arenes/heteroarenes at room temperature under solvent-free conditions and in an air atmosphere. The methodology offers an operational simplicity, high atom economy and environmentally benign procedure. Furthermore, selected compound 3k showed promising anti-inflammatory activity with inhibition nitric oxide and did not exhibit significant cytotoxic effects on macrophage cells.     

Loss of characteristic absorption bands of C60 conjugation systems in the addition with aliphatic amines

The characteristic absorption bands disappear and the shortest band at approximately 244 nm in cyclohexane or 282 nm in toluene remained only with long smoothing tail as C60 reacts adequately with aliphatic amines under sunlight radiation at approximately 40 degrees C. Simultaneously, fluorescence emission shifts from a weak band initially at longer wavelength to another strong one finally at shorter wavelength. The results might imply that the pi-conjugation system of C60 parent molecule is isolated into smaller separated parts. Therefore, some possible isolation models associated with observed experimental results are designed under some reasonable assumptive conditions.     

Synthesis and structure of an air-stable organobismuth triflate complex and its use as a high-efficiency catalyst for the ring opening of epoxides in aqueous media with aromatic amines

An air-stable organobismuth triflate complex with a novel 5,6,7,12-tetrahydrodibenzo[c,f]-[1,5]oxabismocine framework was synthesized and characterized by spectroscopic and single-crystal X-ray diffraction techniques. The organobismuth framework is cationic, and the complex shows relatively strong Lewis acidity (0.8 < H_o ≤ 3.3). It was found to exhibit high catalytic activity towards the ring-opening reaction of epoxides in aqueous media with aromatic amines at room temperature. This catalyst shows good stability, recyclability and reusability. The catalytic system affords a simple and efficient method for the synthesis of β-amino alcohols.