A new and efficient hypervalent iodine−benzyne precursor, (phenyl)[2-(trimethylsilyl)phenyl]iodonium triflate (10), is reported. The hypervalent iodine−benzyne precursor 10 is readily prepared by reaction
of 1,2-bis(trimethylsilyl)benzene with a PhI(OAc)2/TfOH reagent system. Treatment of 10 with Bu4NF in
CH2Cl2 at room temperature gives high yields of the benzyne adducts in the presence of a trapping agent such
as furan, 2-methylfuran, anthracene, tetraphenylcyclopentadienone, or 1,3-diphenylisobenzofuran. Especially,
the result of the reaction in the presence of furan indicates a quantitative generation of benzyne and its efficient
capture by the furan. Similarly, methylbenzynes (22 and 27) are efficiently generated from the corresponding
methyl-substituted (trimethylsilyl)phenyliodonium triflates (12 and 13). The preparation of the hypervalent
iodine−benzyne precursors, the generation of benzynes, the trapping reactions, and the nature are described
in detail together with the advantages of the present reagents over the previously reported benzyne precursors.
(Phenyl)[2‐(trimethylsilyl)phenyl] iodonium triflate
R 1,2‐Dichlorobenzene
I 1, 2‐Bis(trimethylsilyl) benzene 1
R (Diacetoxyiodo) benzene
I (phenyl)[2‐(trimethylsilyl) phenyl] iodonium triflate 2
Furan
P 1, 4‐Dihydronaphthalene 1,4‐oxide 3
The Diels-Alder reaction of methyl 2-pyrone-5-carboxylate and bis(trimethylsilyl)acetylene gave methyl 3,4-bis(trimethylsilyl)-benzoate which was transformed into [5-(methoxycarbonyl)-2-(trimethylsilyl)phenyl](phenyl)iodonium triflate by the reaction with a hypervalent iodine reagent PhI(OAc) 2 /TfOH. The generation and trapping reactions of 4-(methoxycarbonyl)-1,2-didehydrobenzene were successfully conducted by the reaction of the iodonium triflate with Bu 4 NF.
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.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.