Letters in Organic Chemistry - Volume 17, Issue 3, 2020

This study describes a simple multigram-scale procedure for the preparation of (E)-N-(1,7,7- trimethylbicyclo[2.2.1]heptan-2-ylidene)nitramide, nitro-imine 2, by using both classical methods and ultrasound irradiation from 1 utilizing Camphor, a natural product, as starting material. This key intermediate 2, a good building block, is useful to prepare various substances such as terpenoids, reagents for large-scale hydroxylation and amination of organic substrates, and derivatives with anticonvulsant, hypoglycemic, anti-inflammatory, antimicrobial and antiviral activities. It can be transformed into a wide range of other derivatives which can then also be employed in inorganic chemistry. In this work, another useful derivative (E)-2-((1,7,7-trimethylbicyclo[2.2.1]heptan-2-ylidene)amino)ethanol 3 has been prepared from nitro-imine 2 on multigram-scale which also allows access to a variety of products of biological interest after suitable chemical transformations.

Chemical modification of pyridazinone may lead to a potent therapeutic agent. In this study, biological properties of pyridazinone derivatives were evaluated by assessing their antimicrobial and in-vitro antioxidant activities. The reaction of a mucochloric acid and 3-chloro-phenylhydrazine hydrochloride led to the formation of 5-aryl-4-chloro-2-(3-chloro-phenyl)-2H-pyridazin-3-one derivatives 2(a-j). The target compounds were synthesized using nucleophilic substitution reaction. In-silico molecular docking studies of the synthesized compounds were carried out with the help of V-Life Science MDS 4.6 software using GRIP batch docking method to find out which derivative had a better docking. The newly synthesized compounds were characterized by FTIR, 1HNMR, 13C-NMR, MS, and elemental analysis. Antimicrobial and in-vitro antioxidant activity study of the novel synthesized compounds were screened. Compounds 2f and 2g showed good antimicrobial having an MIC 12.5 μg/mL against Staphylococcus aureus and Candida albicans and in-vitro antioxidant activities having an IC50 50.84. The experimental results were further supported by molecular docking analysis with better interaction patterns.

Novel phosphorus compounds bearing fluorine substituted 1,2,4-triazolo[3,2-c][1,2,4]triazine derivatives have been synthesized, starting from ring closure reactions of 3-hydrazino-4-(4'- fluorophenyl)-5-(prydin-4'-yl)-1,2,4-trizole (4) with 1,2-bioxygen compounds followed by the treatment with functional phosphorus compounds. The new systems obtained were evaluated as molluscicidal targets against some snails. Structures of these targets were elucidated upon their elemental and spectral data.

Twelve new 1,2,4-triazole Schiff bases bearing a fluorinated indole ring were successfully synthesized. The 1,2,4-triazole Schiff bases were synthesized from the condensation reaction of 4-amino-5-mercapto-3-[(5-fluoro-2-methyl-1H-indol-3-yl)methyl]-1,2,4-triazole with a series of benzaldehyde derivatives in the presence of (+)-tartaric acid as the catalyst. The structures of Schiff bases were elucidated by FTIR, NMR and mass spectral data. All newly synthesized Schiff bases were screened for their cytotoxic, antibacterial and free radical scavenging activities. Schiff bases 6b, 6c, 6i and 6j with hydroxyl group at ortho or meta position of the phenyl ring demonstrated higher cytotoxic activity against COLO-205 cell lines with IC50 94.0-144.3 μmol/mL. Schiff base bearing 2-OH and 5-Cl groups showed moderate antibacterial activity against Bacillus cereus at MIC 151 μmol/mL. On the other hand, compounds 6b (IC50 150.4 μmol/mL), 6e (IC50 146.4 μmol/mL), 6f (IC50 120.9 μmol/mL) and 6g (IC50 146.2 μmol/mL) displayed a better free radical scavenging activity than the standard BHT.

Various types of isatin derivatives were synthesized by reacting isatin with different reagents viz substituted acetophenones, sodium nitrate, hydroxylamine hydrochloride and hydrazine hydrate. Characterization of the synthesized compounds was done by using various spectral techniques such as IR, 1HNMR, 13CNMR, elemental analysis and mass spectrometry. Synthesized compounds were further evaluated for their antifungal activity against Helminthosporium oryzae, Rhizoctonia solani and Fusarium moniliforme using poison food technique. 3-(2-Oxo-2-phenylethylidene) indolin- 2-one showed significant mycelium inhibition against all tested rice fungi.

A phytochemical investigation of the leaves of Annona reticulata led to the isolation and structural determination of β-sitosterol (1), ent-pimara-8(14),15-dien-19-oic acid (2), ent-pimara- 8(14),15-dien-19-ol (3), quercetin (4), quercetin 3-O-α-L-arabinopyranoside (5), and a mixture of quercetin 3-O-β-D-galactopyranoside (6a) and quercetin 3-O-β-D-glucopyranoside (6b). Of these, compounds 2 and 3 were isolated from the genus Annona for the first time. Compound 3 showed strong cytotoxicity against SK-LU-1 and SW626 cell lines with IC50 values of 17.64 ± 1.07 and 19.79 ± 1.41 μg mL-1, respectively.

The Friedlander reaction is the most commonly used method to synthesis substituted quinolines, the essential intermediates in the medicine industry. A facile one-pot approach for synthesizing substituted quinolines by the reaction of isoxazoles, ammonium formate-Pd/C, concentrated sulfuric acid, methanol and ketones using Friedlander reaction conditions is reported. Procedures for the synthesis of quinoline derivatives were optimized, and the yield was up to 90.4%. The yield of aromatic ketones bearing electron-withdrawing groups was better than the ones with electron-donating substituents. The structures of eight substituted quinolines were characterized by MS, IR, H-NMR and 13CNMR, which were in agreement with the expected structures. The mechanism for the conversion was proposed, which involved the Pd/C catalytic hydrogen transfer reduction of unsaturated five-membered ring of isoxazole to produce ortho-amino aromatic ketones. Then the nucleophilic addition of with carbonyl of the ketones generated Schiff base in situ, which underwent an intermolecular aldol reaction followed by the elimination of H2O to give production of substituted quinolines. This new strategy can be readily applied for the construction of quinolines utilizing a diverse range of ketones and avoids the post-reaction separation of the o-amino aromatic ketone compounds. The conventionally used o-amino aromatic ketone compounds in Friedlander reaction to prepare substituted quinoline are laborious to synthesize and are apt to self-polymerize. While oxazole adopted in this work can be prepared at ease by the condensation of benzoacetonitrile and nitrobenzene derivatives under the catalysis of a strong base. Moreover, the key features of this protocol are readily available starting materials, excellent functional group tolerance, mild reaction conditions, operational simplicity, and feasibility for scaling up.

Cancer is one of the major causes of mortality all around the world. Globally, nearly 1 in 6 deaths is due to cancer. Researchers are trying to synthesize new anticancer agents. Previous studies demonstrated that some pyrazole derivatives could be considered as potential anticancer agents. Herein, ten novel derivatives of 1,5-diarylpyrazole were synthesized in four step reactions and cytotoxic activity was investigated by MTT cell viability assay. All of the compounds were characterized by 1H NMR and 13C NMR and their purity was confirmed by elemental analysis. The cytotoxicity was determined against three cancerous cell lines (HT-29, U87MG and MDA-MB 468) and AGO1522 as a normal cell line. Compound 5a showed the best cytotoxic activity on cancerous cell lines in comparison to paclitaxel. Annexin V/ PI staining assay also showed that compounds 5a and 5i would lead to significant apoptosis induction in MDA-MB 486 cell line.

The pyrolysis of methyl alkyl esters I to III and dithioesters IV to VI were theoretically calculated. All possible pyrolysis paths were considered. Both esters and dithioesters presented three potential paths via six-, four- and five-membered ring transition states, respectively. The calculation processes were calculated using MP2/6-31G(d) set. In-depth theoretical analyses were also presented, including NBO related analyses, synchronicities, and charge distributions, to reveal the detailed pyrolysis process.

A new procedure for the highly regioselective aerobic bromination of aromatic compounds in the presence of copper-based nanoparticles (CuO/ZnO nanocatalyst) under reflux condition is described. Mechanistic parameters are discussed and the plausible mechanism is proposed. Recyclability of the CuO/ZnO nanocatalyst has also been explored upon aerobic bromination of aromatic compounds.

A simple and green method for the synthesis of 1,5-dihydropyrano[2,3-c]chromene derivatives has been reported by three-component reaction of aromatic aldehydes, malononitrile, and 3-hydroxycoumarin in the presence of a series of novel crown ether-based ionic liquids (CE-based ILs) in H2O/EtOH (1:1), under the reflux conditions. The novel CE-based ILs have been synthesized by 18-crown-6 or dibenzo 18-crown-6 chelated with sodium benzenesulfinate derivatives and used as a green and environmental organocatalyst. This method has some advantages such as the aqueous reaction medium, stable catalysts, cleaner reaction profiles and high yield of products in short reaction time.