Reaction of (phenyl) [o-(trimethylsilyl)phenyl]iodonium triflate with organic azides and nitrones using Bu 4 NF gave benzotriazoles and benzisoxazolines in high yields, respectively. This reaction indicates that benzyne is generated under mild conditions and efficiently trapped with the 1,3-dipoles to give heterocyclic compounds.Recently much attention has been paid to the use of hypervalent iodine compounds in organic synthesis (1-7). Previously we have found that (phenyl)[o-(trimethylsilyl)phenyl]iodonium triflate (1) acts as an excellent benzyne precursor and generates benzyne quantitatively by a simple treatment of o-(trimethylsilyl)phenyliodonium triflate 1 with Bu 4 NF under very mild conditions as shown in Scheme 1 (8).The merits of the use of the hypervalent iodine-benzyne precursor 1 includes (a) the stability of the precursor 1, (b) no requirement of a strong base or high temperature, and (c) the quantitative generation of benzyne under mild conditions.If the hypervalent iodine-benzyne precursor 1 can be applied to the reactions with 1,3-dipoles such as azides and nitrones, the reaction of 1 will provides a useful methodology for synthesis of heterocyclic skeletons.In this paper, we report an efficient and convenient synthesis of benzotriazoles and benzisoxazolines by means of the hypervalent iodine-benzyne precursor 1. 1 100% Scheme 1. 205 Brought to you by | Purdue University Libraries Reaction of o-(trimethylsilyl)phenyliodonium triflate 1 with aryl azides (2a-d) could be conducted in CH 2 CI 2 simply by adding Bu 4 NF. A solution of 1 and aryl azides in CH 2 CI 2 was treated with aTHF solution ofBu 4 NF at 0 °C and the reaction mixture was stirred at room temperature for 20 min. Separation by column chromatography on silica gel gave 1-arylbenzotriazoles (3a-d) in high yields. The results are given in Table 1.This reaction was applied to ethyl 2-azidopropionate (2 e)and 2-azido-1-octadecene (21), which reacted with benzyne generated from 1 to yield the corresponding benzotriazoles (3 e and f). As shown in Table 1, o-(trimethylsilyl)phenyliodonium triflate 1 is a useful reagent for benzotriazole synthesis. Even in the reaction of athermally unstable vinyl azide or an azide bearing functional ester group, 1 acts as the benzyne precursor and undergoes the 1,3-dipolar cycloaddition efficiently.Abstract: New synthetic routes for antimicrobial mesoionics 4-methyl-1.3.4-thiadiazolium-2-aminide and 4-aryl-1.3.4thiadiazolium-2-aminide and their precursors are reported. Through the reported procedure, antimicrobial 1,4-diaroylthiosemicarbazides can be obtained in high purity degree.
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