Letters in Organic Chemistry - Volume 19, Issue 5, 2022

A facile synthetic approach to Dakin oxidation utilizing green conditions was demonstrated. A combination of hydrogen peroxide and aqueous choline hydroxide in cooperation with various hydroxyl aryl aldehydes and ketones was used to provide the corresponding dihydric aromatic compounds. The whole procedure was conducted at ambient temperature in an aerobic environment. The scope of ChOH/H2O2 platform was also investigated, showing that the reactivity of the present platform was highly dependent on the position of the hydroxy group of the aromatic ring.

Formamidine derivatives have been synthesized in excellent yields at room temperature from primary amine and N,N-dimethylformamide dimethylacetal (DMF-DMA) in the presence of a catalytic amount of Al-MCM-41 synthesized from natural bentonite as silica and aluminum source. The advantages of this method are the use of a cheap, stable, non-toxic, and readily available catalyst, easy work-up, improved yields, and solvent-free conditions.

An unprecedented protocol for the efficient and highly chemoselective alkylation of unprotected anilines with deactivated CF3-indole-3-carbinols promoted by In(OTf)3 has been developed. A series of diversified trifluoromethylated (indolyl)phenylmethanes were produced featuring the C-alkylation in moderate to high chemical yields and with high regioselectivities.

One of the most prominent aromatic organic chemical compound is Coumarin having formula C9H6O2 which is widely known for its benefits in drug industry. Colourless crystalline solid having sweet scent is coumarin’s physical identity. It serves various purposes such as in synthesis of medicines, laser dyes, perfumes and many more. Having enormous usages, it becomes important to synthesize such compound so various reactions were performed in order to obtain coumarins. This review explicates the preparation of coumarin by Pechmann Condensation and its biological characteristics.

Bismuth (III) nitrate pentahydrate (BN) was found to be a mild and efficient catalyst for the electrophilic condensation of 5-nitroindazole with a wide range of aldehydes to obtain Bis (5-nitro indazolyl) methanes 3 (a-h) at ambient temperature. This was structurally confirmed through FTIR, NMR, and HR-MS technique. Molecular docking studies of all compounds were carried out using breast cancer-causing human estrogen receptor (ER) from Molegro Virtual Docker software. Hydroxy Bis (nitro indazolyl) methanes (3b) were shown better binding affinities and the score obtained was - 150.146 Kcal/mol compared with Tamoxifen drug. The major H-bond interactions were observed with the compound 3f and the value was -5.679. The antimicrobial activity results revealed that compounds 3b and 3d showed promising activity against bacteria Escherichia coli, Klebsiella pneumonia, Staphylococcus aureus, and Pseudomonas aeruginosa and maximum inhibition against Aspergillus niger and Aspergillus flavus. Methoxy derivatives of Bis (nitro indazolyl methanes) (3e) have shown better antioxidant activity and low MIC (6.25 μg/ml) observed for the compounds 3a and 3b. The synthesized compounds have a very promising starting point for the development and improvement of anti-breast cancer drugs.

Finding a sustainable, inexpensive way for Ag-NPs synthesis is considered as one of the most important requirements for industrial application. Oxidized starch was prepared using sodium periodate. Oxidized starch (DAS) was characterized by measuring aldehyde content and using FTIR spectroscopy. DAS was used as a reducing and stabilizing agent for the preparation of Ag nanoparticles (Ag-NPs). Factors that may affect the preparation of Ag-NPs including pH, AgNO3/DAS molar ratio, temperature and time, were studied. UV-Vis. spectroscopy and particle size analysis showed that DAS could act as a reducing and stabilizing agent for the preparation of Ag-NPs and the mean particle size was 19 nm. The so prepared Ag-NPs were used as antibacterial agent for cotton fabric using the pad dry cure method. The results of the antibacterial test showed that the presence of Ag-NPs enhanced the antibacterial properties of the treated cotton fabrics.

Tetrazoles, as one of the most important synthetic heterocyclic compounds, have so many applications in organic chemistry, the photographic industry, coordination chemistry, explosives and in particular, medicinal chemistry. Numerous methods have been reported in the literature for the synthesis of tetrazoles, but much of them have some drawbacks, including the use of strong Lewis acids or expensive and toxic metals and the employment of acidic media. Azides may react with acids to yield toxic and flammable HN3 gas. Furthermore, many methods used high polar solvents such as DMF at high temperatures and very tedious work-up. Heterogeneous catalysts are preferred because of owing to easy handling, safety, recoverability and reusability. Catalyst separation and recycling are highly desirable because catalysts are often very expensive. On the other hand, in spite of higher reactivity and selectivity of homogeneous catalysts, the difficulty of separating them from the reaction medium can lead to the problem of reusing the catalyst. Also, most homogeneous catalysts are thermally unstable. To benefit both types of catalysts, one solution is using nanoparticles. Their higher surface area is the advantage of nanoparticles, which allows them to enhance the reaction rate. Many commercially important catalysts include active nanoparticles spread on high area oxide supports. Such catalysts are highly complex materials that are optimized to work for plenty of turnovers at high reaction rates with high selectivity. Aldehyde (1 mmol), hydroxylamine hydrochloride (0.10 mg, 1.5 mmol), sodium azide (0.10 g, 1.5 mmol), distilled water (5 mL) and nano Al2O3@PCH-Cu (II) (0.01g, 1.04% mol) were added to round bottom flask (25 mL) and stirred at room temperature. After the completion of the reaction, water (10 mL) was added into the reaction mixture and filtered. Excess sodium azide and hydroxylamine hydrochloride are dissolved in water and the catalyst remains on the filter. Extraction of product with diethyl ether (3×10 mL) and then evaporation of ether afforded the product. The product was recrystallized using hot ethanol to obtain pure product. We synthesized a novel, stable, highly reactive and efficient nano-sized heterogeneous catalyst (nano Al2O3@PCH-Cu (II)). We characterized it by FT-IR, ICP, SEM, TGA and EDX analysis. This catalyst was used for the efficient one-pot three-component synthesis of 5-substituted-1H-tetrazoles. A one-pot three-component synthesis of 5-substituted-1H-tetrazoles is conducted, a reaction between various benzaldehydes, hydroxyl amine hydrochloride and sodium azide in the presence of a novel and highly efficient nano alumina supported poly(carboxylic acid hydrazide) Cu(II) complex, nano Al2O3@PCHCu( II), as heterogeneous catalyst in H2O at room temperature. This method has very mild reaction conditions as well as the advantages of easy separation and reusability of the catalyst, very short reaction times, high yields and using H2O as green solvent. Furthermore, using this method, very high TON and TOF values are obtained for all isolated products.

α-Monochlorocyclododecanone was synthesized from cyclododecane and 1,3-Dichloro-5,5- dimethylhydantoin (DCDMH) catalyzed with silica gel in MeOH. The product was obtained by crystallization with a nearly 85% yield. The presented method used cheap raw materials, mild reaction conditions, a simple separation method, and an environment-friendly process. Additionally, the current synthesis provided an ideal approach for large-scale production.

Novel pyrazole tagged pyridine derivatives 5a-n are synthesized starting from 3-cyano-4- trifluoromethyl-6- thiophenyl 2(1H) pyridone 1. Compound 1 on hydrolysis followed by decarboxylation resulted in 4-trifluoro-methyl-6- thiophenyl 2(1H)pyridone 2. Compound 2 was treated with POCl3 to get 2- chloro-4-trifluoromethyl-6- thiophenyl pyridine 3; further reaction with hydrazine hydrate resulting in the formation of compound 4. Compound 4 reacted with different substituted 1,3-diketones in ethanol reflux condition to afford pyrazole substituted pyridine derivatives 5a-n. All derivatives were tested against Gram-positive and Gram-negative bacterial strains and different Candida strains by well diffusion method; compounds 5k and 5l showed significant activity. The binding modes of 5k and 5l were also studied by molecular docking studies.