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- Title
Water-Assisted Nitrile Oxide Cycloadditions: Synthesis of Isoxazoles and Stereoselective Syntheses of Isoxazolines and 1,2,4-Oxadiazoles.
- Authors
Kesornpun, Chatchai; Aree, Thammarat; Mahidol, Chulabhorn; Ruchirawat, Somsak; Kittakoop, Prasat
- Abstract
Conventional methods generate nitrile oxides from oxime halides in organic solvents under basic conditions. However, the present work revealed that water-assisted generation of nitrile oxides proceeds under mild acidic conditions (pH 4-5). Cycloadditions of nitrile oxides with alkynes and alkenes easily occurred in water without using catalysts, thus yielding isoxazoles and isoxazolines, respectively, with excellent stereoselectivity toward five- and six-membered cyclic alkenes. A double stereoselective cycloaddition of two units of a nitrile oxide with cyclohexene was also achieved, thus yielding 1,2,4-oxadiazole derivatives having a unique hybrid isoxazoline-oxadiazole skeleton. Enantiomerically pure isoxazolines were prepared from monoterpenes with a ring strain. In one case, the isoxazoline with a butterfly-like structure was simply prepared, and it might be used as a ligand in asymmetric catalysis.
- Subjects
ISOXAZOLES; NITRILE oxides; ISOXAZOLINE; RING formation (Chemistry); OXADIAZOLES
- Publication
Angewandte Chemie, 2016, Vol 128, Issue 12, p4065
- ISSN
0044-8249
- Publication type
Article
- DOI
10.1002/ange.201511730