Synthesis of 3-Alkylbenzoxazolones from N-Alkyl-N-arylhydroxylamines by Contiguous O-Trichloroacetylation, Trichloroacetoxy ortho-Shift, and Cyclization Sequence
摘要:
Benzoxazolone pharmacophore is present in clinical pharmaceuticals, drug candidates, and many compounds having a wide spectrum of biological activities. The methods available for the synthesis of benzoxazolones have limited diversity due to problems in accessibility and air-sensitivity of diversely substituted o-aminophenols from which they are generally prepared by cyclocarbonylation with phosgene or its equivalents. The present paper describes a mild method for the synthesis of 3-alkylbenzoxazolones from easily accessible and air-stable nitroarenes. Nitroarenes were converted to N-alkyl-N-arylhydroxylamines in two steps involving partial reduction to arylhydroxylamines followed by selective N-alkylation. Treatment of N-alkyl-N-arylhydroxylamines with trichloroacetyl chloride and triethylamine afforded 3-alkylbenzoxazolones generally in good yields through an uninterrupted three-step sequence involving O-trichloroacetylation, N -> C-ortho trichloroacetoxy shift, and cyclization in a single pot at ambient temperatures. The present method is mild, wide in scope, economical, and regioselective. Many sensitive groups like alkyl and aryl esters, amide, cyano, and the carbon-carbon double bond survive the reaction.
We report a H3PO3/I2 mediated formation of N-benzyl benzo heterocyclic ketones from the reaction of benzo heterocyclic compounds with aromatic aldehydes or benzyl alcohol derivatives under metal-free conditions in one-pot. For the first time, aromatic aldehydes were used as benzylated reagents to synthesize benzo heterocyclic ketones in the presence of K2CO3. Control experiments indicated that the
我们报告了 H 3 PO 3 /I 2介导的N-苄基苯并杂环酮的形成,该反应由苯并杂环化合物与芳香醛或苯甲醇衍生物在无金属条件下在一锅中反应。首次以芳香醛为苄基化试剂在K 2 CO 3存在下合成苯并杂环酮。对照实验表明羰基氧最有可能来源于K 2 CO 3。H 3 PO 3还起到促进剂和氢源的双重作用。这种新方法具有底物范围广、成本低、条件简单等特点。
CsF–Celite catalyzed facile N-alkylation of 2(3H)-benzoxazolones and antimicrobial properties of 2-substituted benzoxazole and 3-substituted-2(3H)-benzoxazolone derivatives
作者:M. S. R. Murty、Kesur R. Ram、Rayudu Venkateswara Rao、J. S. Yadav、U. S. N. Murty、K. Pranay Kumar
DOI:10.1007/s00044-010-9367-5
日期:2011.6
The synthesis and antimicrobial activity studies of a new series of cyclic amine containing benzoxazoles and benzoxazolone-2(3H)-ones derivatives were described. The alkylation of benzoxazolone was carried out using cesium fluoride-Celite. The newly synthesized compounds with the influence of the induction of the cyclic amine moiety in the benzoxazole scaffold have been evaluated with respect to the antibacterial and antifungal activity. The 2-cyclic amine-1,3-benzoxazoles (5a-l), 5-chloro-3-alkyl substituted-1,3-benzoxazol-2(3H)-ones (8a-f), and 3-[3-(cyclic amine)propyl]-1,3-benzoxazol-2(3H)-ones (9a-f) were synthesized. These derivatives were tested for antibacterial and antifungal activity. Among the compounds tested, 8c and 9f showed moderate to good antibacterial and antifungal activity. Compound 8a showed good antifungal activity.