Nitro aromatic/nitrophenols have been widely distributed in nature and are mostly isolated from marine microorganisms and had shown a broad spectrum of anti–microbial activities against a wide range of microbial pathogens. The objective of the present work is to Synthesize some new 1,2,3–triazole tethered nitroguiacol ethers and evaluated of their anti–bacterial and anti–fungal activities. A focused library of 1,2,3-triazole tethered nitroguiacol ethers were prepared by employing Cu (I) catalyzed click chemistry reaction and evaluated for their antimicrobial activities by broth microdilution method. Among the tested compounds, compounds 8e, 8f, 8g, and 8i exhibited broad–spectrum activity against selected pathogenic strains, with the MIC of 8 µg/mL for gram–positive bacteria (Staphylococcus aureus), 16 µg/mL for Pseudomonas aeruginosa (gram–negative bacteria), and Candida species, respectively. Future investigations with this class of compounds may lead to the development of potential candidates for antimicrobial drug discovery.Â
Various 2-phenylquinazoline derivatives were synthesized under metal-free conditions from readily available 2-aminophenyl ketones and benzylamines via condensation and oxidative cyclization using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as a versatile reagent. The reaction gave the corresponding 2-phenylquinazoline derivatives in good to excellent yields (up to 92%).2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), a pale yellow solid reagent synthesized by Thiele and Gün-ther in 1906 from benzoquinone, has proved to be a versatile reagent in organic synthesis. 1 Despite remarkable advances in transition-metal catalyzed cross-coupling reactions, the reactions, which involve the formation of C-N bonds, still attract the attention of the research community. In spite of remarkable advances in transition-metalcatalyzed oxidative coupling between sp 3 C-H and primary NH 2 groups leading to the formation of C-N bonds, examples of these coupling reactions under metal-free conditions are rare and they need to be actively pursued to address general problems, such as the use of costly transition-metal catalysts, difficulties in the preparation of ligands or catalysts, and the high toxicity of trace metal impurities which pose serious concerns with regard to the environment. Literature reports 2 indicate that DDQ has been employed elegantly to generate benzylic and naphthylic cations on suitably activated systems through hydride abstraction, with intramolecular cyclization leading to the formation of heterocyclic compounds, and also in oxidative C-C bond formation through the activation of benzylic and allylic carbons. 3Quinazolines and their derivatives are attractive targets for researchers worldwide due to their widespread applications in biology and medicinal chemistry, exhibiting potential therapeutic properties such as anticancer, 4 nuclear translocation induction, 5 ALK5 inhibition, 6 and cannabinoid-1 inverse agonism. 7 These quinazolines also show remarkable activity as antiviral, antitubercular, anticonvulsant, antibacterial, and antidiabetic agents. 8 Due to the significance attached to the quinazoline structural motif, which also occur in many natural products, the development of new methodologies to construct quinazoline moiety is highly desirable. Among known routes to quinazolines, the Bischler cyclization of dicarbonyl compounds with diamines, and oxidative ring closure of 2-aminobenzonitrile with 3-phenylacryloyl chloride under basic conditions 8a,9 are notable. Kotsuki et al. utilized the condensation of cyano-or nitro-activated 2-fluorobenzaldehydes with amidines via a intramolecular nucleophilic substitution reaction to give quinazolines in good yields. 10 Recently, Wang and co-workers described the synthesis of 2-phenylquinazolines using molecular iodine/tert-butyl hydroperoxide as a catalytic system 11a and also by supported copper oxide nanoparticles. 11b A copper-catalyzed Ullmann N-arylation coupling process was reported by Truong and co-workers to synthesize the quinazoline derivatives from 2...
DDQ/TBHP-Induced Oxidative Cyclization Process: A Metal-Free Approach for the Synthesis of 2-Phenylquinazolines. -A novel protocol is presented which starts from 2-aminophenyl ketones and benzylamines via condensation and oxidative cyclization. -(RACHAKONDA, S.; PRATAP, P. S.; RAO*, M. V. B.; Synthesis 2012, 13, 2065-2069, http://dx.doi.org/10.1055/s-0031-1289768 ; Dep. Chem., Krishna Univ., Machilipatnam 521 001, India; Eng.) -Mais 42-174
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