Phenyl 4,5-Dichloro-6-Oxopyridazine-1(6H)-Carboxylate as Carbonyl Source: Facile and Selective Synthesis of Carbamates and Ureas under Mild Conditions

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.

Design, Synthesis, ADME, and Anticancer Studies of Newer N-Aryl-5-(3,4,5-Trifluorophenyl)-1,3,4-Oxadiazol-2-Amines: An Insight into Experimental and Theoretical Investigations

In continuance of our investigation into the anticancer activity of oxadiazoles, we report here the preparation of 10 new 1,3,4-oxadiazole analogues using the scaffold hopping technique. We have prepared the oxadiazoles having a common pharmacophoric structure (oxadiazole linked aryl nucleus) as seen in the reported anticancer agents IMC-038525 (tubulin inhibitor), IMC-094332 (tubulin inhibitor), and FATB (isosteric replacement of the S of thiadiazole with the O of oxadiazole). All of the oxadiazole analogues were predicted for their absorption, distribution, metabolism, and excretion (ADME) profiles and toxicity studies. All of the compounds were found to follow Lipinski's rule of 5 with a safe toxicity profile (Class IV compound) against immunotoxicity, mutagenicity, and toxicity. All of the compounds were synthesized and characterized using spectral data, followed by their anticancer activity tested in a single-dose assay at 10 μM as reported by the National Cancer Institute (NCI US) Protocol against nearly 59 cancer cell lines obtained from nine panels, including non-small-cell lung, ovarian, breast, central nervous system (CNS), colon, leukemia, prostate, and cancer melanoma. N-(2,4-Dimethylphenyl)-5-(3,4,5-trifluorophenyl)-1,3,4-oxadiazol-2-amine (6h) displayed significant anticancer activity against SNB-19, OVCAR-8, and NCI-H40 with percent growth inhibitions (PGIs) of 86.61, 85.26, and 75.99 and moderate anticancer activity against HOP-92, SNB-75, ACHN, NCI/ADR-RES, 786-O, A549/ATCC, HCT-116, MDA-MB-231, and SF-295 with PGIs of 67.55, 65.46, 59.09, 59.02, 57.88, 56.88, 56.53, 56.4, and 51.88, respectively. The compound 6h also registered better anticancer activity than Imatinib against CNS, ovarian, renal, breast, prostate, and melanoma cancers with average PGIs of 56.18, 40.41, 36.36, 27.61, 22.61, and 10.33, respectively. Molecular docking against tubulin, one of the appealing cancer targets, demonstrated an efficient binding within the binding site of combretastatin A4. The ligand 6h (docking score = -8.144 kcal/mol) interacted π-cationically with the residue Lys352 (with the oxadiazole ring). Furthermore, molecular dynamic (MD) simulation studies in complex with the tubulin-combretastatin A4 protein and ligand 6h were performed to examine the dynamic stability and conformational behavior.

Phenyloxycarbonyl (Phoc) Carbamate: Chemioselective Reactivity and Tetra-n-butylammonium Fluoride Deprotection Study

We present the results of the chemoselective reactivity of phenylcarbamates. Phenylcarbamates of primary amines are reactive to form urea, and phenylcarbamates of secondary amines can be used as tags due to the existence of rotamers. Moreover, deprotection attempts to to recover the primary amines in use of a catalytic amount of TBAF show the possibility of obtaining the symmetrical urea from the corresponding phenylcarbamate. We have begun the study of the transformation of Phoc carbamates into the corresponding free amines by TBAF. We present here our most significant results concerning the sensitivity of this reaction in terms of the solvent and substrate.

Urea Derivatives in Modern Drug Discovery and Medicinal Chemistry

The urea functionality is inherent to numerous bioactive compounds, including a variety of clinically approved therapies. Urea containing compounds are increasingly used in medicinal chemistry and drug design in order to establish key drug-target interactions and fine-tune crucial drug-like properties. In this perspective, we highlight physicochemical and conformational properties of urea derivatives. We provide outlines of traditional reagents and chemical procedures for the preparation of ureas. Also, we discuss newly developed methodologies mainly aimed at overcoming safety issues associated with traditional synthesis. Finally, we provide a broad overview of urea-based medicinally relevant compounds, ranging from approved drugs to recent medicinal chemistry developments.

Spontaneous and Direct Transformation of N,O-Diaryl Carbamates into N,N'-Diarylureas

We have discovered a spontaneous reaction of N,O-diaryl carbamates to afford symmetrical N,N'-diarylureas. Optimization of the conditions indicated that N,N-dimethylformamide (DMF) was the best solvent and triethylamine (Et₃N) was the best additive for this transformation. The reaction requires the presence of aryl groups on the nitrogen and oxygen atoms of carbamates. Substrates bearing an electron-donating methoxy group on either of the aryl groups reacted slowly under these conditions.

Recent Progress in the Chemistry of Pyridazinones for Functional Group Transformations

While N-hetereocycles have received significant attention in organic synthesis and other research fields, the chemistry of pyridazine, a six-membered aromatic ring with two adjacent nitrogen atoms, and its derivatives has been relatively little understood. This Synopsis describes recent progress made in the synthesis of pyridazine derivatives-particularly, pyridazin-3(2H)-ones-and their utility as efficient and recyclable functional group carriers for various important organic reactions.

Scalable, One-Pot, Microwave-Accelerated Tandem Synthesis of Unsymmetrical Urea Derivatives

We report a facile, microwave-accelerated, one-pot tandem synthesis of unsymmetrical ureas via a Curtius rearrangement. In this method, one-pot microwave irradiation of commercially available (hetero)aromatic acids and amines in the presence of diphenylphosphoryl azide enabled extremely rapid (1-5 min) construction of an array of unsymmetrical ureas in good to excellent yields. We demonstrate the utility of our method in the efficient, gram-scale synthesis of key biologically active compounds targeting the cannabinoid 1 and α7 nicotinic acetylcholine receptors.

Crystal structure of tert-butyl 2-phenylethylcarbamate, C13H19NO2

C13H19NO2, monoclinic, P21/n (no. 14), a = 5.2692(3) Å, b = 13.8663(9) Å, c = 17.8020(13) Å, β = 93.323(6)°, V = 1298.50(15), Z = 4, R gt(F) = 0.0590, wR ref(F 2) = 0.1932, T = 293 K.

Imidazolin-2-iminato Ligand-Supported Titanium Complexes as Catalysts for the Synthesis of Urea Derivatives

The reactions of tetrakis(dimethylamido)titanium(IV) [Ti(NMe2)4] with three different imidazolin-2-imines (Im(R)NH; R = tert-butyl (tBu), mesityl (Mes), and 2,6-diisopropylphenyl (Dipp)) afforded the corresponding titanium imidazolin-2-iminato complexes [(Im(R)N)Ti(NMe2)3] (R = tBu, 1a; R = Mes, 1b; R = Dipp, 1c). Treatment of complex 1a with two different carbodiimides [R'N═C═NR'; R' = cyclohexyl (Cy) and isopropyl (iPr)] resulted in the formation of imidazolin-2-iminato titanium mono(guanidinate) complex of the type [(Im(R)N)Ti(R'NC(NMe2)NR') (NMe2)2 (R' = iPr; R = tBu (2a), R = Dipp (2c); R' = Cy, R = tBu (3a)], as yellow solid in 94% yield. However, a similar reaction of 1b and 1c with 2 equiv of phenyl isocyanates at ambient temperature resulted in the formation of corresponding titanium bis(ureate) complexes [(Im(R)N)Ti{κ(2)-OC(NMe2)NPh}2(NMe2)] (R = Mes, 4b and R = Dipp, 4c). Three equivalents of phenyl isothiocyanate reacted with complex 1c to afford respective titanium tris(thioureate) complex [(Im(Dipp)N)Ti{κ(2)-SC(NMe2)NPh}2{κ(1)-SC(NMe2)NPh}] (6c). The molecular structures of 1a-c, 2a, 2c, 3a, 4c, and 6c were established by X-ray diffraction analyses, and, from the solid-state structures of 1a-c, 2a, 2c, 3a, 4c, and 6c, it was confirmed that the imidazolin-2-iminato titanium bond in each case is very short and possesses a multiple-bonding character. The imidazolin-2-iminato titanium complex 1c was utilized as a precatalyst for the addition of amine N-H bond to phenyl isocyanate. High yields of the corresponding urea derivatives were achieved under mild conditions. The mechanistic study of the aforementioned catalytic reaction was performed, and the active catalyst complex 7b was isolated using 2 equiv of iminopyrrole [2-(2,6-iPr2C6H3N═CH)C4H3NH] and the complex 4b. The molecular structure of 7b was thereafter established.