Copper-catalyzed aerobic oxidative cross-dehydrogenative coupling of amine and α-carbonyl aldehyde: a practical and efficient approach to α-ketoamides with wide substrate scope

A copper-catalyzed aerobic oxidative cross-dehydrogenative coupling (CDC) of amine with α-carbonyl aldehyde has been developed. Many types of amines are tolerant in this transformation leading to various α-ketoamides compounds. Wide substrate scope, CDC strategy and using air as oxidant make this transformation highly efficient and practical. Molecular oxygen acts not only as the oxidant, but also as an initiator to trigger this catalytic process. Furthermore, mechanism studies show that carbonyl group of α-carbonyl aldehyde plays a role as the directing group to facilitate this chemical process.     

An efficient synthesis of α-hydroxyphosphonates and α-aminophosphonates in the presence of chlorotrimethylsilane

Abstract

Solvent free, and quantitative yielding synthesis of α-hydroxyphosphonates (2a–h) from 2-chloroquinolin-3-carbaldehyde (1a–h) and α-aminophosphonates (4a–p) from imines (3a–p), obtained from 2-chloroquinoline-3-carbaldehyde by using triethylphosphite in the presence of chlorotrimethylsilane at room temperature in short time.     

Sulfated polyborate catalyzed Kabachnik-Fields reaction: An efficient and eco-friendly protocol for synthesis of α-amino phosphonates

An efficient, and environmentally benign protocol for a three-component Kabachnik-Fields reaction of aldehydes, amines, and diethyl phosphite catalyzed by sulfated polyborate has been described to afford α-amino phosphonates under solvent-free reaction conditions. The major advantages of the present method are high yields, short reaction time, simple work-up procedure, inexpensive, eco-friendly and reusable catalyst and solvent-free reaction conditions and tolerance towards various functional groups present in the substrates.     

Optimization of α-amylase production for the green synthesis of gold nanoparticles

Biocompatible gold nanoparticles have received considerable attention in recent years because of their promising applications in bioimaging, biosensors, biolabels, and biomedicine. The generation of gold nanoparticles using extra-cellular α-amylase for the reduction of AuCl₄ with the retention of enzymatic activity in the complex is being reported. The enhanced synthesis of particles has been brought about by optimizing the medium components for α-amylase. Response surface methodology and central composite rotary design (CCRD) were employed to optimize a fermentation medium for the production of α-amylase by Bacillus licheniformis at pH 8. The three variables involved in the study of α-amylase were fructose, peptone and soya meal. Only fructose had a significant effect on α-amylase production. The most optimum medium (medB) containing (%) fructose: 3, peptone: 1, soya meal: 2, resulted in a amylase activity of 201.381 U/ml which is same as that of the central level. The least optimum (medA) and most optimum (medB) media were compared for the synthesis of particles indicated by difference in color formation. Spectrophotometric analysis revealed that the particles exhibited a peak at 582 nm and the A₅₈₂ for the Med B was 8-fold greater than that of the Med A. The TEM analysis revealed that the particle size ranged from 10 to 50 nm.     

Alum： An efficient catalyst for one-pot synthesis of α-aminophosphonates

Alum (KAl(SO ₄) ₂·12H ₂O) is an inexpensive, efficient, non-toxic and mild catalyst for the one-pot synthesis of α-aminophosphonates.A three component reaction of an aldehyde/ketone, an amine and triethyl phosphite was carried out under solvent-free conditions to afford the corresponding a-aminophosphonates in short reaction times and high yields with the green aspects by avoiding toxic catalysts and solvents.     

An eco-friendly procedure for the efficient synthesis of dialkyl α-aminophosphonates in aqueous media

A new, convenient and high yielding procedure for the preparation of diethyl α-aminophosphonates in water by one-pot reaction of aldehydes, amines, tri/dialkyl phosphites in the presence of a low catalytic amount of [Cu(3,4-tmtppa)](MeSO₄)₄ (0.16 mol%) as a highly stable and re-usable catalyst is described.     

An efficient synthesis of substituted alkyl acrylates using α-keto amides

The addition of α-keto amides as a NH-acid to alkyl propiolates and dialkyl acetylenedicarboxylates in the presence of a catalytic amount of triphenylphosphine gives the corresponding substituted alkyl acrylates.     

Amberlite-IR 120 catalyzed three-component synthesis of α-amino phosphonates in one-pot

A simple, efficient, and environmentally benign method for a three-component reaction of an amine, an aldehyde or a ketone, and diethyl phosphite catalyzed by Amberlite-IR 120 resin has been developed to afford α-amino phosphonates in high yields and short reaction times under solvent-free reaction conditions. The major advantages of the present method are good yields, inexpensive, ecofriendly and reusable catalyst, mild and solvent-free reaction conditions and tolerance towards various functionalities present in the substrates.     

Brønsted base-modulated regioselectivity in the aerobic oxidative amination of styrene catalyzed by palladium

Palladium(II)-catalyzed aerobic oxidative amination of styrene with oxazolidinone proceeds with catalyst-controlled regioselectivity: (CH3CN)2PdCl2 (1) and (Et3N)2PdCl2 (2) catalyze formation of the anti-Markovnikov and Markovnikov enecarbamate products, 3 and 4, respectively. Kinetic studies and deuterium kinetic isotope effects demonstrate that these two reactions possess different rate-limiting steps, and the data indicate that the product regiochemistry arises from the presence or absence of an effective Br?nsted base in the reaction. In the presence of a Br?nsted base such as triethylamine or acetate, the kinetically preferred Markovnikov aminopalladation adduct of styrene is trapped via rapid deprotonation of a zwitterionic intermediate and leads to formation of 4. In the absence of an effective Br?nsted base, however, slow deprotonation of this adduct enables aminopalladation to be reversible, and product formation proceeds through the thermodynamically preferred anti-Markovnikov aminopalladation adduct to yield 3.     

An efficient synthesis of β-aminoketone compounds through three-component Mannich reaction catalyzed by calcium chloride

Abstract  

Various β-aminoketones were synthesized in a three-component reaction of ketones, aldehydes, and amines in the presence of calcium chloride as catalyst in ethanol in high yields as compared to other synthetic methods. The advantages of this new method are a short reaction time (2 h), high yields, easy workup, convenience, low cost, and eco-friendly protocol.     

Colorimetric detection of cadmium in water using L-cysteine Functionalized gold–silver nanoparticles

Abstract

A new simple colorimetric assay was developed for the selective and sensitive detection of cadmium (II) in water samples using L-cysteine functionalized gold–silver nanoparticles. The gold–silver nanoparticles were synthesized by reducing HAuCl₄ and AgNO₃ in aqueous medium and were further functionalized with L-cysteine. The formation of homogeneous gold–silver nanoparticles was characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, particle size distribution, and ultraviolet–visible absorption methods. In the presence of cadmium (II), the aggregation of functionalized gold–silver nanoparticles caused by the interaction between cadmium (II) and L-cysteine resulted in a naked-eye visible color change of L-cysteine functionalized gold–silver nanoparticles from orange–yellow to green, which can be monitored by a simple ultraviolet–visible spectrophotometer. Under the optimal conditions, the absorbance ratio at 600–435?nm (A₆₀₀/A₄₃₅) was linear to the concentration of cadmium (II) from 0.4 to 38.6?μM, and the limit of detection of cadmium (II) was 44?nM. Interference measurements showed that the method exhibited good selectivity. The proposed method was successfully applied to the determination of cadmium (II) in environmental water samples. The results indicated that this simple, selective, and sensitive sensing system has good potential for practical applications.     

Highly efficient synthesis of α-amino amidines from ynamides by the Cu-catalyzed three-component coupling reactions

Using ynamides as one of the reacting components, the Cu-catalyzed three-component reaction of sulfonyl or phosphoryl azides and amines affords α-amino amidines in high yields under mild conditions. Synthetic utility of the produced compounds was demonstrated in the diastereoselective alkylation of α-amino amidines bearing a chiral oxazolidinone moiety. It was also shown that α-amino imidates could be readily prepared by employing alcohols instead of amines.     

Copper-catalyzed oxidative coupling of carboxylic acids with formamides for the synthesis of α,β-unsaturated amides

A novel and efficient protocol for the synthesis of α,β-unsaturated amides has been developed using catalytic amount of Cu(OAc)₂ and TBHP as an available oxidant. Oxidative coupling of various unsaturated carboxylic acids with N,N-disubstituted formamides was examined to furnish the desired products in good yields.     

K2PdCl4 catalyzed efficient multicomponent synthesis of α-aminonitriles in aqueous media

An efficient, mild and environmentally friendly method has been developed for the Strecker reaction to synthesize α-aminonitriles in the presence of K₂PdCl₄ as a catalyst. The three-component one-pot condensation of an aldehyde, amine and trimethylsilyl cyanide proceeded smoothly in water to afford the corresponding product in high yield with short reaction times.     

Aerobic ligand-free domino Suzuki coupling—Michael addition reaction catalyzed by in situ generated palladium nanoparticles in water: a general method for the synthesis of benzo[c]chromene derivatives

A general method has been developed for the synthesis of benzo[c]chromene derivatives via aerobic ligand-free domino Suzuki coupling and Michael addition reaction catalyzed by in situ generated palladium nanoparticles in water leading to C–C and C–O bond formations simultaneously.     

NBS-assisted an efficient conversion of styrenes to α-hydroxy ketones in water

An expedient, mild and environmentally benign method for the oxidation of styrenes to α-hydroxy ketones has been developed. This conversion has been achieved by employing water as a solvent as well as an oxygen source. This facile and efficient tandem process provides α-hydroxy ketones in moderate to good yields from easily accessible styrenes.     

An efficient synthesis of 2-isoxazolines from α-haloketone oximes and dimethyl sulfonium salts

2-Isoxazolines were synthesized efficiently from a formal [4+1] cycloaddition of nitrosoalkenes and sulfur ylides, which were generated in situ from α-haloketone oximes and dimethyl sulfonium salts. This approach provides a new method to synthesize a range of 2-isoxazolines in high yields and high regioselectivity.     

An efficient and general route to the synthesis of diethyl α,α-bromofluorophosphonates

An efficient and general two-step halogenation procedure to prepare diethyl α,α-bromofluorophosphonates was described, which included bromination by PPh₃, 2,3-dichloro-5,6-dicyanobenzquinone (DDQ) and n-Bu₄NBr, and electrophilic fluorination by N-fluorobisbenzenesulfonimide (NFSI). Both aromatic and aliphatic α,α-bromofluorophosphonates could be prepared by this method.