Ultrasound-assisted synthesis of functionalized arylacetylenes

Novel carbazolyl-thiazolyl-chromone and carbazolyl-thiazolyl-pyrazole hybrids: synthesis, cytotoxicity evaluation and molecular docking studies

A simple synthetic method was performed to design a novel series of polycyclic systems consisting of carbazole-thiazolidinone-chromone hybrids 4a-e and carbazole-thiazolidinone-pyrazole hybrids 5a-e in excellent yields. The methodology depended on the one-pot four-component reaction of 3-amino-9-ethylcarbazole, substituted isothiocyanates, ethyl bromoacetate and 6-methyl-3-formylchromone in ethanol under ultrasound waves at 50 °C to give the carbazole-thiazolidinone-chromone hybrids 4a-e. The latter isolated products were treated with hydrazine hydrate in ethanol under ultrasound waves at 50 °C affording the corresponding carbazole-thiazolidinone-pyrazole hybrids 5a-e. Spectral and analytical data confirmed the structures of all the synthesized compounds. The target compounds were screened for their in vitro anticancer activities against HCT116, PC3 and HepG2 cancer cell lines using the standard SRB method. Fortunately, both compounds 5dand5e were the most active against all cancer cell lines compared with doxorubicin and can be promising anticancer agents. Both bioactive products 5band5e were studied by the molecular docking to see how they bind with VEGFR-2 receptor. The results indicated that those compounds exhibited high affinities towards VEGFR-2 and established remarkably similar interactions to those of the powerful VEGFR-2-KDR.

Direct methylthiolation of C-, S-, and P-nucleophiles with sodium S-methyl thiosulfate

A practical and efficient methylthiolation that employed the typical Bunte salt sodium S-methyl sulfothioate as the sulfur source was described. This reagent could react with a variety of compounds such as alkynes, 1,3-diketones, thiols, selenol and H-phosphine oxides, affording methylthiolated products in moderate to excellent yields. The advantages such as easy preparation, air- and moisture-stability and high tolerance of functional groups demonstrated the potential of this reagent to be widely applied in organic synthesis. Notably, the robustness of this reagent was demonstrated by the late-stage modification of drug molecules of erlotinib.

Propargylation of CoQ0 through the Redox Chain Reaction

An efficient catalytic propargylation of CoQ0 is described by employing the cooperative effect of Sc(OTf)₃ and Hantzsch ester. It is suggested to work through the redox chain reaction, which involves hydroquinone and dimeric propargylic moiety intermediates. A broad range of propargylic alcohols can be converted into the appropriate derivatives of CoQ0 containing triple bonds in good to excellent yields. The mechanism of the given transformation is also discussed.

Synthesis of ynones at room temperature catalyzed by copper chloride cryptand complex under solvent free conditions

An air-stable highly efficient reusable CuCl₂-cryptand-[2.2.Benzo] catalyst is reported first time for coupling reaction of terminal alkynes with different acyl chlorides in the presence of triethylamine acting both as base and solvent at room temperature to give the corresponding ynones. Easy-going, short reaction time, cost-effective, palladium-, phosphorus- and solvent-free, high yield and recyclability up to 5^th times make this method green procedure for ynones’ synthesis with wide substrate variety.

Intensification of paracetamol (acetaminophen) synthesis from hydroquinone using ultrasound

Paracetamol (acetaminophen) is one of the most frequently used analgesic and antipyretic drugs. This work deals with ultrasound assisted synthesis (UAS) of paracetamol from hydroquinone using ammonium acetate as an amidating agent. The optimization of various reaction and ultrasound parameters was performed to minimize the energy and time requirement. UAS of paracetamol was achieved at a lower temperature (60 °C) and the time (150 min) without formation of salt as a byproduct, making reaction green and inherently safer. On the other hand, the conventional process requires high reaction temperature (220 °C) and time (15 h). The quantification of the product was done by using high performance liquid chromatography (HPLC). Optimization of parameters revealed that the percent yield of 57.72% can be obtained in 150 min by performing the reaction in the ultrasound bath at 22 kHz frequency, 60 °C temperature, hydroquinone to ammonium acetate and acetic acid in a molar ratio of 1:6:5, 125 W power, 50% duty cycle and agitation speed of 300 RPM. Hence, ultrasound assisted synthesis can be considered as a process intensification tool for the synthesis of paracetamol and possibly other pharmaceutical compounds.

Hypervalent Iodine Mediated Chemoselective Iodination of Alkynes

Reported herein are practical approaches for the chemoselective mono-, di-, and tri-iodination of alkynes based on efficient oxidative iodinations catalyzed by hypervalent iodine reagents. The reaction conditions were systematically optimized by altering the iodine source and/or the hypervalent iodine reagent system. The tetrabutylammonium iodide (TBAI)/(diacetoxyiodo)benzene (PIDA) system is specific for monoiodination, while the KI/PIDA system results in di-iodination. Combining the TBAI/PIDA and KI/PIDA systems in one pot provided the corresponding tri-iodination products efficiently. These reaction conditions can be applied to the synthetically important iodination of aromatic and aliphatic alkynes, which was accomplished in good yield (up to 99%) and excellent chemoselectivity. These synthetic methods can also be applied to the efficient chemoselective synthesis of iodoalkyne derivatives, intermediates, and related biologically active compounds.

Rh(iii)- or Ir(iii)-catalyzed ynone synthesis from aldehydes via chelation-assisted C–H bond activation

A simple and practical synthesis of ynones directly from readily available aldehydes was developed for the first time under mild reaction conditions via a Rh(iii)- or Ir(iii)-catalyzed formyl C–H bond activation.

Ultrasound assisted efficient conversion of aromatic aldehydes from oximes

This work describes the ultrasound-assisted regeneration of aldehydes from oximes in ethanol and phosphoric acid as mediator of the reaction. The large scale regeneration of benzaldehyde was shown under similar conditions. The products were isolated in good yields after short reaction times under mild conditions.

Regio- and stereoselective synthesis of 1,4-dienes

Titanocene(II)-promoted cross-coupling between (Z)-alkenyl methyl sulfones and terminal allenes produced 1,4-dienes regioselectively via the formation of 2-alkylidenetitanacyclopentanes. Preferential formation of E,Z-dienes was observed in the reaction using aryl-, amino-, and phosphinylallenes.

Ultrasound promoted greener synthesis of 2-(3,5-diaryl-4,5-dihydro-1H-pyrazol-1-yl)-4-phenylthiazoles

A rapid and cleaner procedure for the synthesis of a series of 2-(3,5-diaryl-4,5-dihydro-1H-pyrazol-1-yl)-4-phenylthiazoles under ultrasonic irradiation in ethanol is described.

Ultrasound-assisted synthesis of dihydropyrimidine-2-thiones

Chalcone derivatives were prepared by the condensation of various substituted aryl aldehydes and acetophenone in alkaline ethanol, while pyrimidine-2-thione derivatives were prepared by the combination of chalcones and thiourea under conventional and ultrasonic conditions. Advantages of the ultrasound effect were observed and high yields of the products were obtained after 20-30 min sonication. Characterization and structural elucidation of the products was realized based on chemical, analytical and spectral analyses. The results clearly demonstrated a high efficiency of the ultrasonic systems was achieved in the chemical processes.

Efficient sonochemical synthesis of novel 3,5-diaryl-4,5-dihydro-1H-pyrazole-1-carboximidamides

An ultrasound-assisted preparation of a series of novel 3,5-diaryl-4,5-dihydro-1H-pyrazole-1-carboximidamides that proceeds via the efficient reaction of chalcones with aminoguanidine hydrochloride under clean conditions is described.

Sono-thermal oxidation of dihydropyrimidinones

Combination of ultrasound and heat has been used for the oxidation of some ethyl 3,4-dihydropyrimidin-2(1H)-one-5-carboxylates to their corresponding ethyl pyrimidin-2(1H)-one-5-carboxylates by using potassium peroxydisulfate in aqueous acetonitrile. An ultrasonic probe of 24 kHz frequency has been used for this study. Whereas the use of ultrasound increases the rate of reactions compared with reactions at reflux conditions, the nature of 4-substituent on the dihydropyrimidinone ring affects also the rate of reaction.