Eco-Friendly Syntheses of 2-Substituted Benzoxazoles and 2-Substituted Benzothiazoles from 2-Aminophenols, 2-Aminothiophenols and DMF Derivatives in the Presence of Imidazolium Chloride

One-pot Synthesis of 2,3-disubstituted-4(3H)-quinazolinone from o-aminobenzoic Acid and DMF Derivatives using Imidazole Hydrochloride as a Promoter

As a novel and environmentally friendly Brönsted acid, imidazole hydrochloride was used to promote the synthesis of 2,3-disubstituted-4(3H)-quinazolinone from o-aminobenzoic acid and DMF derivatives. The essence of this reaction is a multicomponent reaction, which constructs multiple chemical bonds between different components through the transamidation of imidazole hydrochloride. This protocol showed a wide range of functional group tolerance, and a series of quinazolinones were synthesized in low to moderate yields without metal catalysts, oxidants or other additives.

Rapid and Simple Microwave-Assisted Synthesis of Benzoxazoles Catalyzed by [CholineCl][Oxalic Acid]

Microwave irradiation has been used to enhance the reaction yields and selectivities for organic transformation. In this paper, microwave irradiation (MW) was investigated for the environmentally benign synthesis of benzoxazoles through the cyclization of 2-aminophenols and benzaldehydes using deep eutectic solvent (DES) as a catalyst. The [CholineCl][oxalic acid] was easily synthesized from choline chloride with oxalic acid and used without further purification. [CholineCl][oxalic acid] catalyzed the synthesis of benzoxazoles to produce the desired product in a good to excellent conversion and selectivity under MW irradiation. The presence of [CholineCl][oxalic acid] helps to promote the rapid heating transfer from microwave irradiation into the reaction mixture. The [CholineCl][oxalic acid] can be recovered and reused several times without a considerable degradation in catalytic activity.

Synthetic Approaches to Biologically Active C-2-Substituted Benzothiazoles

Numerous benzothiazole derivatives are used in organic synthesis, in various industrial and consumer products, and in drugs, with a wide spectrum of biological activity. As the properties of the benzothiazole moiety are strongly affected by the nature and position of substitutions, in this review, covering the literature from 2016, we focus on C-2-substituted benzothiazoles, including the methods of their synthesis, structural modification, reaction mechanisms, and possible pharmacological activity. The synthetic approaches to these heterocycles include both traditional multistep reactions and one-pot atom economy processes using green chemistry principles and easily available reagents. Special attention is paid to the methods of the thiazole ring closure and chemical modification by the introduction of pharmacophore groups.

Synthesis, anticancer evaluation and molecular docking of new benzothiazole scaffolds targeting FGFR-1

This work deals with the design and synthesis of a series of new substituted 2-arylbenzothiazole compounds attached to 4-oxothiazolidin-2-ylidene ring 2-12 and chain elongation with different amino acids and their corresponding ester derivatives 13-18. All prepared derivatives were screened for their in vitro cytotoxicity activities against two cancer cell lines (HepG-2 and MCF-7) in comparison with doxorubicin; in addition to their safety towards thenormal cell line. Furthermore, all compounds 2-18 were evaluated as FGFR-1 inhibitors using AZD4547 as a reference. The 4-oxothiazolidin-2-ylidene derivatives 3 and 8 exhibited the highest cytotoxic activity (IC_{50 HepG-2} = 2.06, 2.21 µM and IC_{50 MCF-7} = 0.73, 0.77 µM, respectively) through their promising FGFR-1 suppression effects (IC₅₀ = 16.31 and 18.08 nM, respectively) in comparison to AZD4547 (IC₅₀ = 21.45 nM). Cell cycle and apoptosis analysis indicated that compounds 3 and 8 induce pronounced increase in the cell percentages at pre-G₁ and G₂/M phase compared to the untreated MCF-7 cancer cells, in addition to their up regulation of caspase-3/7/9. The molecular docking simulation was created to elucidate the binding modes of benzothiazole derivatives 1-18 bearing various scaffolds within the ATP-binding pocket of FGFR-1 enzyme compared with AZD4547.

A green approach for the synthesis of 2-substituted benzoxazoles and benzothiazoles via coupling/cyclization reactions

We have developed the green method for the synthesis of benzoxazoles and benzothiazoles with moderate to good yields using imidazolium chlorozincate (II) ionic liquid supported into Fe3O4 nanoparticles (LAIL@MNP) under solvent-free sonication. The reaction was performed under mild conditions and only produced water as a sole byproduct. The reactions under solvent-free sonication showed advantages of faster reaction rate (30 min) and high yields of the products (up to 90%). Moreover, the LAIL@MNP material was easily separated from the reaction mixture and can be recycled for five consecutive runs with a slight decrease in its catalytic performance (from 82 to 73%).

Benzothiazoles from Condensation of o-Aminothiophenoles with Carboxylic Acids and Their Derivatives: A Review

Nowadays, organic chemists are interested in the field of heterocyclic chemistry due to its use in the synthesis of a great variety of biologically active compounds. Heterocyclic compounds are widely found in nature and are essential for life. Among these, some natural nitrogen containing heterocyclic compounds have been used as chemotherapeutic agents. Their attachment to sugar molecules either as thioglycosides or as nucleosides analogues plays an important role in vital biological processes as well as in synthetic organic chemistry. Molecules containing benzothiazole (BT) nuclei are of this interesting class of compounds because some of them have been found to have a wide variety of biological activities. In this sense, we selected this topic to review and to then summarize the procedures related to the condensation reactions of o-aminothiophenoles (ATPs) as well as their disulfides with carboxylic acids, esters, orthoesters, acyl chlorides, amides, and nitriles. The condensation reactions with carbon dioxide (CO₂) are included. Conventional methods with the use of acid and metal catalysts as well as recent green techniques, such as microwave irradiation, the use of ionic liquids, and ultrasound (US) chemistry, which have proven to have many advantages, were found in the review.