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- Title
Strong deshielding in aromatic isoxazolines.
- Authors
Ungvarská Maľučká, Lucia; Vilková, Mária; Kožíšek, Jozef; Imrich, Ján
- Abstract
Very strong proton deshielding was found in di/tri-aromatic isoxazoline regioisomers prepared from acridin-4-yl dipolarophiles and stable benzonitrile oxides (BNO). Three alkenes, (acridin-4-yl)-CHCH-R (R = COOCH3, Ph, and CONH2), reacted with three BNO dipoles (2,4,6-trimethoxy, 2,4,6-trimethyl, 2,6-dichloro) to give pairs of target isoxazolines with acridine bound to C-4 or C-5 carbon of the isoxazoline (denoted as 4-Acr or 5-Acr). Regioselectivity was dependent on both the dipolarophile and dipole character. The ester and amide dipolarophile displayed variable regioselectivity in cycloadditions whereas the styrene one afforded prevailing 4-Acr regioisomers. 2,4,6-Trimethoxy-BNO was most prone to form 5-Acr isoxazolines while mesitonitrile oxide gave major 4-Acr isoxazolines. Basic hydrolysis of the amide cycloadduct led to an unexpected isoxazolone product. The structure of the target compounds was studied by NMR, MS, and X-ray crystallography. Copyright © 2015 John Wiley & Sons, Ltd.
- Subjects
ISOXAZOLINE; REGIOSELECTIVITY (Chemistry); BENZONITRILE; ACRIDINE derivatives; RING formation (Chemistry); NUCLEAR magnetic resonance spectroscopy; X-ray crystallography; AROMATIC compounds spectra
- Publication
Magnetic Resonance in Chemistry, 2016, Vol 54, Issue 1, p17
- ISSN
0749-1581
- Publication type
Article
- DOI
10.1002/mrc.4308