Letters in Organic Chemistry - Volume 17, Issue 4, 2020

A practical procedure for the addition of arylboronic acids to aromatic aldehydes has been developed in the presence of NiCl2(PPh3)2/1,3-bis-(2,6-diisopropylphenyl)imidazolium chloride (IPr·HCl) system with good yield. Generally, electron-rich and -neutral aryl aldehydes showed excellent reactivity and provided desired products in high yields. This procedure will provide new way to the synthesis of diarylmethanols.

Synthesis of some 1,1'-diaryl-3,3'-(p-phenylenedicarbonyl)dithioureas was accomplished in two steps. Dithioureas were prepared under inert conditions with significantly high yields. Inhibitory activity of dithiourea compounds was investigated against urease enzyme. All the synthesized compounds were evaluated for their urease inhibitory activities, and molecular docking studies were carried out to ascertain the inhibitor binding mode with the enzyme. All the compounds displayed moderate to significant urease inhibitory activities.

The selectivity and molecular mechanism of the intramolecular [3+2] cycloaddition (IMDC) reaction of nitrone-alkene generated from m-allyloxybenzaldehyde has been studied computationally using B3LYP/6-31G(d) theoretical method. The energy profiles indicate that this IMDC reaction favours kinetically the formation of the fused-endo, as observed experimentally. The solvent has no influence on the mechanism and selectivity, but it increases slightly the activation energy and decreases the exothermic character of this IMDC reaction. The analysis through electron localisation function (ELF) of the favourable fused-endo pathway shows that the formation of the C–O and C–C new bonds occurred via a non-concerted synchronous one-step mechanism. The analysis of noncovalent interaction using Non-covalent interaction (NCI) and QTAIM analyses of the structure of the fused-endo transition state indicates that the hydrogen-bond formed at this approach is the origin for the favouring of the fused-endo pathway.

Gold nanoparticle functionalized mesoporous silica-chitosan (Au NPs/silica-chitosan) as an environmentally benign and heterogeneous nanocatalyst was prepared and its properties were characterized using field emission scanning electron microscopy (FE-SEM) and fourier transform infrared (FT-IR). The catalytic activity of Au NPs/silica-chitosan was studied in the synthesis of biologically important 4H-pyran derivatives. In these reactions, efficient and green syntheses of 4H-pyrans were carried out using isatins or aldehydes, active methylene compounds, and 1,3-dicarbonyl compounds in the presence of a catalytic amount of Au NPs/silica-chitosan in water in excellent yields. Au NPs/silica-chitosan can be recovered easily and reused without any significant loss of the catalytic activity. 4H-pyran derivatives were synthesized using Au NPs/silica-chitosan as catalyst in three component reaction of isatins/aldehydes, active methylene, and 1,3-dicarbonyl compounds in water. Au NPs/Silica-Chitosan was prepared by reaction of aqueous solution of HAuCl4 (1 wt.%) and solution chitosan in deionized water and acetic acid with tetraethyl ortho silicate (TEOS) at 100ºC for 24 h. Gold nanoparticle functionalized mesoporous silica-chitosan was prepared and its catalytic activity was investigated for forming 4H-pyran derivatives. In this study, active methylene and 1,3-dicarbonyl compounds reacted with various isatins and aldehydes which afforded the corresponding spirooxindoles with 88-98% yields. This method includes the environmentally friendly reaction conditions, short reaction time, simple work-up, excellent yield, broad scope of usable substrates, recovery and reusability of heterogeneous catalyst.

Various 4-amino-5-cyanopyrimidines were readily prepared in a few minutes with good yields through a one-pot, three-component reaction of aldehydes, malononitrile and amidines in aqueous media in the presence of catalytic amounts of potassium carbonate. Short reaction times, high efficiency, generality of the method, synthesis of new derivatives, inexpensiveness, and non-toxicity of the catalyst/solvent are the interesting features of this method, which make it eco-friendly and highly attractive.

This paper presents synthesis of vancomycin derivatives modified with selected 1- and 2-aminoalditols to carboxylic function and 2,5-anhydro-D-mannose and D-talose to amino function of vancosamine via reductive alkylation. MIC and MBC of these derivatives were determined for reference strains of bacteria: Staphylococcus aureus ATCC 25923, ATCC 6538, ATCC 6538/P, S. epidemidis ATCC 14490, E. faecium PCM 1859, E. faecalis PCM 2673, S. pyogenes PCM 465, and S. pneumonia ATCC 49619 and compared with the activity of vancomycin and its aglycone. Our findings confirm that sugar fragments can play an important role in the mechanism of interaction of vancomycin with bacterial cell wall peptidoglycan.

A series of novel 5H-Thiochromeno[4,3-d]pyrimidine derivatives were synthesized, purified and characterized by different spectroscopy techniques such as 1H NMR, 13C NMR, Mass and Elemental Analysis. The new compounds were evaluated for their anti-cervical cancer activity on Human Cervical Cell Line HeLa. They were found to be potent anti-cervical cancer agents with GI50 values less than 10 μg/mL with respect to positive control drug Adriamycin.

We present an efficient method for the synthesis of quinazolin-4(3H)-ones via Pdcatalyzed carbonylation-cyclization of N′-(2-bromophenyl)benzamidines. Chloroform cleanly generated CO under mild conditions. This method allows for the carbonylation-cyclization of N′-(2- bromophenyl)benzamidines in the presence of Pd(OAc)2 to give quinazolin-4(3H)-ones in good to excellent yields.

A series of 1,2,4-triazole and 1,2,4- thiadiazole derivatives were prepared starting from ethyl 4-(3-methyl-5-oxo-1,5-dihydro-4H-1,2,4-triazol-4-yl)benzoate. Firstly, both ethyl ester groups were simultaneously transformed into hydrazide groups, then into thiosemicarbazide groups using both microwave- assisted and conventional methods. The latter products were interacted with NaOH and H2SO4 to form ring assemblies containing two 1,2,4-triazole and 1,3,4-thiadiazole fragments, respectively. Antioxidant activities of the synthesized compounds were determined with CUPRAC, ABTS, and DPPH assays. Most of the compounds showed significant antioxidant activity and especially, compound 3 exhibited very good SC50 value for DPPH method and compound 3, 4a, 5a exhibited very high scavenging activity to the ABTS method. In addition, the in silico analysis was carried out with the synthesized derivatives to understand the mode of interaction with superoxide dismutase (SOD) and human tyrosine kinase using docking protocols in order to find out the most active antioxidant drug having high inhibitory activity in cancer.

A simple and environmentally benign room temperature synthesis of 1,2,4-triazolidine-3- thiones is described using Envirocat EPZ-10R as a solid acid catalyst in the aqueous medium. The use of Envirocat EPZ-10R as a green catalyst, reusability of the catalyst, water as a universal solvent and good yields of the product are the attractive features of the present method.