Letters in Organic Chemistry - Current Issue

In oxidative coupling, two molecules combine with the help of different oxidants and transition metals. It is used to form various natural and synthetic compounds. Oxidative coupling reactions catalyzed by transition metals (Pd or Cu), Iodine, Cobalt, Ti, etc, are used widely for the synthesis of pyrroles. Pyrrole is a 5-membered heterocyclic ring structure that consists of a single nitrogen. Several methods have been adopted and reported for the synthesis of pyrroles and their analogs in the recent past. Synthesis of pyrrole via oxidative coupling takes place in the presence of various catalysts, bases, and solvents and at different temperatures and times. In another method, Oxidative reactions between diols and primary amines utilizing copper/nitroxyl as the catalyst also yield pyrroles. Rhodium has also been used as a catalyst in oxidative coupling reactions between alkynes and carboxylic acid (substituted by heteroarene or arene) to obtain pyrroles. Paal-Knorr reaction is also one of the most common reactions in the synthesis of pyrrole. In the present study, we summarized different oxidative reactions that have been reported for the synthesis of pyrrole. Hopefully, the study will be helpful for the researchers.

The acyl urea functionality and related analogs are increasingly used in medicinal chemistry and drug design to prove well-defined pharmacological actions and optimal physicochemical properties. This review paper aimed to summarize information related to synthesis methods of acyl urea derivatives, marketed products, and patents to explore their applications in counteracting CNS-related diseases by multiple targeting. Comprehensive data related to acyl urea and related compounds of the last 15 years is collected from various resources to provide enormous information to the readers. The content of the study uniformly includes considerable evidence linked to the common and unique synthesis techniques of acyl urea from starting materials like benzamide, isocyanates, substituted iodoglycals, 2 chloro nicotinic acid, and methyl hydrazines, as well as patents related to the same. This work describes the reactions of several substrates that can be used to manufacture various acyl urea derivatives. An understanding of patents related to acyl urea analogs with specific targets for CNS action may also help researchers working on additional synthesis of acyl urea derivatives with potential CNS action.

A novel series of Apigenin bioisosteres [1(4-chlorophenyl)-3-phenyl prop-2-ene-1-one] non-cyclic derivatives (4a-4c) and [7-hydroxy-2-phenyl-4H-chromen-4-one] cyclic derivatives (9a- 9d) were synthesized. The newly synthesized apigenin bioisosteres were confirmed using UV, IR, NMR, and mass spectroscopic methods. The antioxidant, antibacterial, and anti-cancer activities of all newly synthesized compounds were assessed using the DPPH free radical scavenging capacity, disc diffusion method, and in vitro MTT assay on the human breast cancer MCF-7 cell line. Almost all the synthesized apigenin bioisosteres had greater antioxidant and antimicrobial activity than standard Apigenin. Out of seven compounds (4a-4c and 9a-9d), five compounds were found to exhibit notable antiproliferative activity on the breast cancer cell line (MCF-7), whereas two compounds, 9c and 9d, did not show notable activity. Our analysis suggests that synthesized Apigenin bioisosteres function as prospective antioxidant, antimicrobial, and anticancer agents.

New calamitic liquid crystals, 4-[{[4-(diethylamino)phenyl]methylidene}amino]phenyl 4- alkyloxybenzoate (nEABAA) containing mesogenic core system which made of three phenyl rings were reported. The ester and imine linkages connected the phenyl rings. At one end of the molecule, the core system was attached to an alkyloxy chain with a variable length -(CH2)n- (where n = 2-10, 12, 14, 16 and 18). At the other end of the molecule, the para position of the phenyl ring is bonded to the diethylamino group. The molecular structure of the current compounds was confirmed by using spectroscopic methods. The mesomorphic characteristics of the title compounds were studied by using a differential scanning calorimeter and a polarizing optical microscope attached to a heating stage. Through observation under microscopy, it was found that all synthesized compounds exhibited only a single (nematic) phase. The exhibition of the monophase variance (nematic) in the current compounds is caused by the presence of the diethylamino group that is attached to the terminal position of the benzylideneaniline core system. The diethylamino group has caused the molecular breadth to increase and this results in a weaker overall lateral intermolecular attraction. Subsequently, it depressed the mesophase thermal stability of the compounds. Thermal properties of the current compounds were compared with the earlier reported analogous and the structure-property relationships of the current compounds have been inferred through this comparison.

Dehydro-7,8-aryl-himachalene is a desired natural benzocycloheptene sesquiterpene found in the essential oil of Atlas cedar (Cedrus atlantica) in minor quantities. Herein, we report a simple and environmentally benign synthesis of this molecule via the aromatization of himachalene mixture (the major constituent of the same oil). The synthesis of the desired compound has been achieved by iodine/DMSO-mediated aromatization. The synthesized product has been characterized using MS spectrometry and NMR spectroscopy data. The treatment of the himachalene mixture with iodine led to the formation of dehydro-7,8-arylhimachalene, along with other rearrangement products catalyzed by the hydroiodic acid formed in situ. The use of DMSO as a co-solvent enabled the elimination of the acid formed and the regeneration of iodine. The optimization of the reaction conditions led to the formation of the desired product with a good yield. The present study highlights the development of a simple and environmentally benign method for the synthesis of a natural benzocycloheptene-based sesquiterpenoid in large quantities in order to explore its biological and chemical properties.

A highly efficient and simple cross-coupling reaction of N-aryl aluminum reagents with Naryl thiosuccinimides for the synthesis of diarylsulide derivatives using CuCl (20 mol%) as a catalyst is reported. Under the optimum reaction conditions, the coupling reaction between aryl aluminum reagents with different substituents and N-aryl thiosuccinimides with different substituents can be carried out smoothly with 18-94% isolated yields of diarylsulides. The method avoids the use of expensive transition metals, such as Pd, Ir, or Rh, phosphine ligands, and has the advantages of simple operation and high reaction efficiency. The structures of all the target compounds are confirmed by ¹HNMR and ¹³CNMR.

Our current work's primary goal is to create novel heterogeneous gallium sulfide (Ga2S3) nanocatalysts and investigate their catalytic activity in the synthesis of 3,3-(arylmethylene)-bis-(4- hydroxycoumarin) derivatives without use of solvent. FT-IR, XRD, SEM, and EDX analysis characterized the synthesized gallium sulfide (Ga2S3) nanomaterial catalysts. This method's main benefits are its short reaction time, solvent-free conditions, extremely mild reaction conditions, good product yield, and, most importantly, its ability to recover catalysts after at least four runs.