Bromodimethylsulfonium bromide (BDMS)-mediated Lossen rearrangement: synthesis of unsymmetrical ureas

Innovations in isocyanate synthesis for a sustainable future

Isocyanates play a crucial role as key building blocks in the production of thermoplastic foams, elastomers, adhesives, agrochemicals, and pharmaceuticals. These compounds are essential in the manufacture of various polymeric products, such as polyurethane foams, synthetic rubbers, and surface coatings. Given their significance, and the fact that many isocyanates are highly reactive and toxic, there is an increasing demand for innovative and sustainable methods for their synthesis and detection that emphasize safety, efficiency, and selectivity. Developing processes for isocyanate production that avoid hazardous reagents like phosgene is particularly critical. While several methods exist for the in situ generation of isocyanates, the search for an eco-friendly and sustainable approach for their direct synthesis and isolation continues. Recent advances in isocyanate synthesis promise innovative and efficient strategies with broad industrial and environmental benefits. This review highlights various methods for synthesizing di- and monoisocyanates, emphasizing their isolation and conversion into ureas and carbamates in line with the principles of sustainable and green chemistry.

Amide Synthesis from Decarboxylative Coupling of Isocyanates and Carboxylic Acids

Isocyanates are versatile electrophiles that can react with a wide range of nucleophiles to afford important organic structures. Although the reactions between isocyanates and alcohols, amines and organometallic reagents have been well established, the synthesis of amides through the decarboxylative condensation of carboxylic acids and isocyanates is less appreciated. In this review, the synthesis of isocyanates and its application on amide synthesis through the condensation with carboxylic acids are summarized and discussed. It is our hope that this review will attract more attention to this less mentioned transformation and inspire new developments in the fields of organic synthesis, polymer synthesis and chemical biology.

Green, facile synthesis and evaluation of unsymmetrical carbamide derivatives as antimicrobial and anticancer agents with mechanistic insights

A very practical method for the synthesis of unsymmetrical carbamide derivatives in good to excellent yield was presented, without the need for any catalyst and at room temperature. Using a facile and robust protocol, fifteen unsymmetrical carbamide derivatives (9-23) bearing different aliphatic amine moieties were designed and synthesized by the reaction of secondary aliphatic amines with isocyanate derivatives in the presence of acetonitrile as an appropriate solvent in good to excellent yields. Trusted instruments like IR, mass spectrometry, NMR spectra, and elemental analyses were employed to validate the purity and chemical structures of the synthesized compounds. All the synthesized compounds were tested as antimicrobial agents against some clinically bacterial pathogens such as Salmonella typhimurium, Bacillus subtilis, Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans. Compounds 15, 16, 17, 19 and 22 showed potent antimicrobial activity with promising MIC values compared to the positive controls. Moreover, compounds 15 and 22 provide a potent lipid peroxidation (LPO) of the bacterial cell wall. On the other hand, we investigated the anti-proliferative activity of compounds 9-23 against selected human cancerous cell lines of breast (MCF-7), colon (HCT-116), and lung (A549) relative to healthy noncancerous control skin fibroblast cells (BJ-1). The mechanism of their cytotoxic activity has been also examined by immunoassaying the levels of key anti- and pro-apoptotic protein markers. The results of MTT assay revealed that compounds 10, 13, 21, 22 and 23 possessed highly cytotoxic effects. Out of these, three synthesized compounds 13, 21 and 22 showed cytotoxicity with IC50 values (13, IC50 = 62.4 ± 0.128 and 22, IC50 = 91.6 ± 0.112 µM, respectively, on MCF-7), (13, IC50 = 43.5 ± 0.15 and 21, IC50 = 38.5 ± 0.17 µM, respectively, on HCT-116). Cell cycle and apoptosis/necrosis assays demonstrated that compounds 13 and 22 induced S and G2/M phase cell cycle arrest in MCF-7 cells, while only compound 13 had this effect on HCT-116 cells. Furthermore, compound 13 exhibited the greatest potency in inducing apoptosis in both cell lines compared to compounds 21 and 22. Docking studies indicated that compounds 10, 13, 21 and 23 could potentially inhibit enzymes and exert promising antimicrobial effects, as evidenced by their lower binding energies and various types of interactions observed at the active sites of key enzymes such as Sterol 14-demethylase of C. albicans, Dihydropteroate synthase of S. aureus, LasR of P. aeruginosa, Glucosamine-6-phosphate synthase of K. pneumenia and Gyrase B of B. subtilis. Moreover, 13, 21, and 22 demonstrated minimal binding energy and favorable affinity towards the active pocket of anticancer receptor proteins, including CDK2, EGFR, Erα, Topoisomerase II and VEGFFR. Physicochemical properties, drug-likeness, and ADME (absorption, distribution, metabolism, excretion, and toxicity) parameters of the selected compounds were also computed.

Direct additive-free N-formylation and N-acylation of anilines and synthesis of urea derivatives using green, efficient, and reusable deep eutectic solvent ([ChCl][ZnCl2]2)

In the current report, we introduce a simple, mild efficient and green protocol for N-formylation and N-acetylation of anilines using formamide, formic acid, and acetic acid as inexpensive, nontoxic, and easily available starting materials just with heating along stirring in [ChCl][ZnCl2]2 as a durable, reusable deep eutectic solvent (DES), which acts as a dual catalyst and solvent system to produce a wide range of formanilides and acetanilides. Also, a variety of unsymmetrical urea derivatives were synthesized by the reaction of phenyl isocyanate with a range of amine compounds using this benign DES in high to excellent yields. [ChCl][ZnCl2]2 showed good recycling and reusability up to four runs without considerable loss of its catalytic activity.

Mechanosynthesis of Polyureas and Studies of Their Responses to Anions

Polyureas (PUs) have already found wide practical applications, and various methods of their synthesis have been reported. In this manuscript, we wished to report the very first mechanochemical approach towards aromatic PUs via reactions between isomeric 2,2'-, 3,3'-, and 4,4'-diaminobiphenyls and triphosgene under solvent-free conditions following ball-milling. By using this synthetic approach, both PUs and azomethine-capped Pus were obtained. The fluorescence response of the above-mentioned PUs towards various anions in solutions were studied and selective fluorescence responses towards the hydroxyl and fluoride anions were observed.

The Lossen rearrangement from free hydroxamic acids

During more than a century, the Lossen rearrangement was supposed to occur exclusively in the presence of stochiometric amount of activating reagents. Very recently, it was demonstrated that the Lossen rearrangement can take place directly from free hydroxamic acids offering a renewal of interest for this reaction.

Use of Bromine and Bromo-Organic Compounds in Organic Synthesis

Bromination is one of the most important transformations in organic synthesis and can be carried out using bromine and many other bromo compounds. Use of molecular bromine in organic synthesis is well-known. However, due to the hazardous nature of bromine, enormous growth has been witnessed in the past several decades for the development of solid bromine carriers. This review outlines the use of bromine and different bromo-organic compounds in organic synthesis. The applications of bromine, a total of 107 bromo-organic compounds, 11 other brominating agents, and a few natural bromine sources were incorporated. The scope of these reagents for various organic transformations such as bromination, cohalogenation, oxidation, cyclization, ring-opening reactions, substitution, rearrangement, hydrolysis, catalysis, etc. has been described briefly to highlight important aspects of the bromo-organic compounds in organic synthesis.

A base-mediated self-propagative Lossen rearrangement of hydroxamic acids for the efficient and facile synthesis of aromatic and aliphatic primary amines

A variety of aromatic and aliphatic hydroxamic acids were converted to the corresponding primary amines via base-mediated rearrangement.

A Simple and Efficient Synthesis of Diaryl Ureas with Reduction of the Intermediate Isocyanate by Triethylamine

Thirty symmetrical diaryl urea derivatives were synthesised in moderate to excellent yields from arylamine and triphosgene with triethylamine as a reducing agent for the intermediate, isocyanate. It was significant that part of the products could be collected in almost quantitative yield without column chromatography. The procedure under mild reaction conditions was tolerant of a wide range of functional groups. The structures of the compounds were determined by NMR, MS and X-ray crystallographic analyses.