Accelerated Amination of Baylis–Hillman Acetates Under Ultrasound Irradiation

The amination of the Baylis–Hillman acetates with primary amines can be dramatically promoted with improved yields and shortened reaction time under ultrasound irradiation. The selected aromatic, heteroaromatic, and aliphatic amines were investigated as the effective candidates for the sonochemical transformation.     

Cerium(IV) ammonium nitrate (CAN) catalyzed aza-Michael addition of amines to α,β-unsaturated electrophiles

Cerium(IV) ammonium nitrate (CAN) catalyzed facile and efficient aza-Michael addition of aromatic and aliphatic amines with α,β-unsaturated electrophiles in the absence of solvent under ultrasound irradiation.     

Microwave and Ultrasound Irradiation‐Assisted Synthesis of Novel Disaccharide‐Derived Arylsulfonyl Thiosemicarbazides

The synthesis of 1‐arylsulfonyl‐4‐(1′‐N‐hepta‐O‐acetyl‐β‐lactosyl)thiosemicarbazides by reaction of hepta‐O‐acetyl‐α‐D‐lactosyl isothiocyanate with substituted phenylsulfonyl hydrazines has been shown to occur in less than 1 min under microwave activation and 8 min under ultrasound irradiation at room temperature. It is noteworthy that when ultrasound and microwaves (MW) were utilized, a cleaner reaction accompanied with higher yields was observed.     

Facile reaction of thiols and amines with alkyl 4-hydroxy-2-alkynoates in water under neutral conditions and ultrasound irradiation

This Letter describes an alternative protocol for the Michael addition of thiols to 4-hydroxy-2-alkynoates. The reaction proceeds at room temperature in water under ultrasound irradiation. With amines instead of thiols a sequential conjugate addition/lactonization reaction leads to important 4-amino-furan-2-one derivatives.     

Porous Calcium Hydroxyapatite as an Efficient Catalyst for Synthesis of Pyrazolines via 1,3‐Dipolar Cycoloaddition Under Solvent‐Free Microwave Irradiation

Adsorbed on porous calcium hydroxyapatite, 1,3‐dipolar cycloaddition of diphenylnitrilimine on olefins is readily catalyzed under solvent‐free microwaves irradiation. The pyrazolines are obtained in few minutes with high yields. Specific surface of porous calcium hydroxyapatite and microwaves effects are discussed.     

Microwaves-assisted solvent-free synthesis of N-acetamides by amidation or aminolysis

The preparation of acetamides directly from amines and an acetyl donor under microwaves without any catalyst is described. The inexpensive, solvent free, and fast reaction conditions are the important features of this procedure.     

1-取代胺甲基-7,8-二去氢-4-羟基-3,7-二甲氧基-17-甲基-9α,13α,14α-吗啡烷-6-酮的合成

超声波辐射下, 以盐酸青藤碱为原料, 在其A环1-位碳上进行Mannich反应, 合成了2个新的取代胺甲基化合物 1a, 1b. 且由化合物1a与取代芳胺及吗啉通过胺交换反应合成了8个新的取代胺甲基化合物2a～2h. 所有新化合物的结构利用IR, MS, ¹H NMR及NOE差谱进行了表征.     

Palladium‐Catalyzed Heteroaromatic Couplings Mediated by Microwave Irradiation

Nitrogen‐containing heterocycles bearing a halogen substituent have been converted to the corresponding amines by a synthetic protocol based on Buchwald methodology assisted by microwaves.     

An ultrasound-promoted green approach for the N-formylation of amines under solvent- and catalyst-free conditions at room temperature

A new environmentally benign, convenient, and facile methodology for the N-formylation of amines is reported using ultrasound irradiation under solvent- and catalyst-free conditions at room temperature. Compared with conventional methods, the main advantages of the present procedure are milder, cleaner and greener conditions, shorter reaction time, higher purity and yields, simpler work-up, and lower generation of waste or pollutions.     

Ultrasound promoted three-component synthesis of dihydroindeno[1,2-b]pyrrole derivatives

In this work, a one-pot three-component reaction of ninhydrin, primary amines, and 1,3-dicarbonyl compounds was investigated under various conditions to synthesis of diverse derivatives of dihydroindeno[1,2-b]pyrroles. Catalyst-free conditions in EtOH under ultrasound irradiation (45% of amplitude) were selected as a novel and efficient method for synthesis of these fused structures. The reactivity of different primary amines was then investigated for steric and electronic effects. Two examples of difunctional structures were also synthesized by using of 1,4-diaminobenzene under optimum conditions with high yields. The structure of all products was characterized by spectroscopic methods and elemental analysis.     

Facile synthesis of 4-nitro-N-substituted-1,8-naphthalimide derivatives using ultrasound in aqueous media

This study describes the ultrasound-assisted synthesis of 4-nitro-N-substituted-1,8-naphthalimide derivatives from 4-nitro-1,8-naphthalic anhydride and related amines by irradiating at 35 KHz in a sonic bath in aqueous media at room temperature. The results obtained by this method are comparable to those obtained by a common reflux method. The imidation reaction under ultrasound irradiation preceded 8 and 20 times faster than the common method and produced higher yields.     

Ultrasound and microwave-assisted extraction of metals from sediment: a comparison with the BCR procedure

In this paper we investigate alternatives to mechanical stirring for the extraction of the mobile fraction of metals from sediment, and analyze whether these techniques can reduce extraction time and improve reproducibility. We compare the quantities of metal extracted from BCR601 and BCR701 certified sediments using ultrasound bath, microwave-assisted extraction and the first step in the certified BCR sequential extraction procedure. Some environmentally important not-certified metals such as As, Mn, Co, Fe and Al have been included in this study. In the case of microwave-assisted extraction, we compare tests in which samples are exposed to constant, low power irradiation with tests using pulsed high power.

In the tests using the ultrasound bath, less metal was extracted than with the other extractive techniques and standard deviations were comparable to those obtained with the BCR procedure; in assays using microwaves at constant power, extraction efficiencies were different for different metals and for different reference materials and, in some cases, standard deviations were higher than those for the reference method. In contrast, tests with microwaves and constant temperature produced encouraging results: R.S.D.s lay in the 2–4% range, both for certified and not-certified metals; these values are very low compared to those for the reference method. Extraction efficiencies for certified metals were close to 100% for Cd, Zn, Cu and Ni and around 80% for Pb and Cr.     

Thiamine hydrochloride(VB1):An efficient catalyst for one-pot synthesis of α-aminophosphonates under ultrasonic irradiation

An efficient synthesis of novelα-aminophosphonates by the reaction of aldehydes and amines with triethyl phosphite in the presence of the easily available,inexpensive,and nontoxic catalyst thiamine hydrochloride(VB1).This method affords theα-aminopho-sphonates under the influence of ultrasound irradiation in aqueous medium,in short reaction times(4-6 min),high yields(85-95%), with improved purity.The process is green,mild,inexpensive and excellent yields are the main compensation of this procedure.     

Ultrasound assisted diazotization and diazo coupling reactions using trichlorotriazine

A high rate and efficient procedure for the synthesis of azo dyes has been developed. This concluded the sequential diazotization-diazo condensation of aromatic amines such as 4,4′-sulfonyldianiline with NaNO₂, or trichlorotriazine with coupling agents under ultrasound irradiation at room temperature. This method applied to several types of coupling agents led to corresponding azo dyes in high yield within short reaction time. The mild reaction conditions and inexpensive procedure are clear advantages of this method.     

Ultrasound-irradiated Michael addition of amines to ferrocenylenones under solvent-free and catalyst-free conditions at room temperature

A facile Michael addition of ferrocenylenones with aliphatic amines under ultrasound irradiation in the absence of solvent and catalyst at room temperature can afford 1-ferrocenyl-3-amino carbonyl compounds rapidly in high yields, which is also efficient in the aza-Michael reaction of other α,β-unsaturated carbonyl compounds such as chalcone, carboxylic ester, etc. However, aromatic amines do not undergo the conjugate addition at all, and the reactions under existing methods do not proceed or take place in low yield after a long reaction time. Apart from experimental simplicity, generality and selectivity, the advantages of this methodology are the rapid, environmentally benign and less expensive processes, which will contribute to the progress of green chemistry.     

Can "microwave effects" be explained by enhanced diffusion?

The "microwave effect" or non-thermal effects due to microwaves have been the subject of intense debate. This paper explores the following hypothesis: if the transport of an active species is a rate limiting step in a reaction, and if microwaves enhance the diffusion of that species, then the overall reaction rate would change under microwave heating compared with conventional heating. If the hypothesis is correct then it should be possible to pick those reactions that would speed up, slow down or stay the same, under microwave irradiation. One consequence of the hypothesis is that the equilibrium states (end point of the reactions) remain unchanged by microwave irradiation. The measurements and theory presented here strongly suggest that this hypothesis is correct.     

Microwave Assisted,Highly Efficient Solid state N- and S-Alkylation

Secondary amines and thiophenols were alkylated with alkyl and benzyl halides rapidly on alumina supported potassium carbonate under solvent-free conditions using microwaves. Equimolar amounts of the secondary amine/thiophenol and alkyl halide were used. The procedure neither required any strong base nor a PTC. Aniline was also monobenzylated with benzylchloride. Separation of the products from the reactants was very simple by using a nonpolar solvent for desorption.     

Influence of microwave irradiation on enzyme kinetics

The in vitro effect of 2.45 GHz microwave irradiation on porcine pepsin activity under controlled temperature and absorbed microwave power via kinetic parameters was evaluated. Kinetic study with respect of time of irradiation demonstrated the existence of an inactivation effect of microwaves at pH 2 on pepsin molecule. Bovine serum albumin (BSA)-bromphenol blue (BPB) complex was used as substrate for the assay of pepsin by kinetic method. Depending on absorbed microwave dose, the degree of caused inactivation varies from 39.11 to 45.91% for 5 and 20 min of pepsin MW irradiation, respectively. The V _maxapp and K _mapp were calculated for low (5 min of MW irradiation) and higher specific absorbed dose (20 min of MW irradiation), as well as for untreated enzyme, from double reciprocal Lineweaver-Burk plot. The effect of microwaves on substrate (BSA-BPB complex) was also investigated. For reaction performed with MW irradiated substrate for 5 min the reaction rate was decreased for 15.15%, while for 20 min of substrate irradiation reaction rate was decreased for 25.52% compared to the control reaction. The article is published in the original.     

Microwave-assisted cyclic amidine synthesis using TiCl4

Microwave-assisted treatment of various heterocyclic amides (benzodiazepinone, phthalazone) with TiCl(4) in the presence of primary or secondary amines provides the corresponding amidines. In addition to the interest of the microwaves for this reaction, our study highlights the higher reactivity of the cyclic acetamide moiety compared to the cyclic benzamide moiety towards this TiCl(4)-mediated reaction.     

Combined protocol for the analysis of polycyclic aromatic hydrocarbons (PAHs) and polychlorobiphenyls (PCBs) from sediments using focussed microwave assisted (FMW) extraction at atmospheric pressure

A microwave-assisted protocol has been developed using focussed microwaves at atmospheric pressure for the extraction of PAHs and PCBs from sediments. It combines extraction and purification assisted by microwaves. This protocol has been applied to the quantification of 12 individual PAHs, 8 individual PCBs and 8 PCB coeluted mixtures from two Standard Reference Materials and one natural sediment. The results for both classes of compounds (PAHs and PCBs) are good in terms of recoveries, which are always greater than 70% and in most cases around 100%. The reproducibility is also good with coefficients of variation below 10% in most cases. This protocol has the great advantage of saving time, the time dedicated to the preparation / extraction assisted by microwaves being reduced to less than half an hour.