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- Title
Naphtho[1,8- de ][1,2]Oxazin-4-ol: Precursor to 1,2,8-Trisubstituted Naphthalenes and 1-Unsubstituted Naphtho[1,2- d ]isoxazole 2-Oxide: A Novel Isomerization of the N -Oxide to Nitrile Oxide en Route to Isoxazol(in)es.
- Authors
Gerontitis, Ioannis E.; Tsoungas, Petros G.; Varvounis, George
- Abstract
Naphtho[1,8-de][1,2]oxazin-4-ol and its acyl or benzyl derivatives ring open to various 2,8-dihydroxy-1-naphthonitriles, which, through (de)protection protocols and reduction, afford the target (E)-2-hydroxy-8-methoxy-1-naphthaldehyde. This was converted to its corresponding oxime, which was oxidatively o-cyclized with phenyliodine(III) diacetate (PIDA) to 9-methoxynaphtho[1,2-d]isoxazole 2-oxide. The latter, in deuterated DMSO at room temperature, was rearranged to its isomer 2-hydroxy-8-methoxy(naphthalen-1-yl)nitrile oxide. The isomerization was detected by time-course plot 1H NMR spectroscopy and further identified from its 13C NMR and HRMS spectra. The nitrile oxide was stable in (non)deuterated DMSO for at least 18 h. A 3,4-bis(2-hydroxy-8-methoxynaphthalen-1-yl)-1,2,5-oxadiazole 2-oxide, as a dimerization product or an isocyanate as a rearrangement isomer, was ruled out, the former by its HRMS spectrum and the latter by its 1,3-dipolar cycloaddition reactions to substituted isoxazoles.
- Subjects
NITRILE oxides; ISOMERIZATION; RING formation (Chemistry); NAPHTHALENE; NUCLEAR magnetic resonance spectroscopy; ISOXAZOLES; ISOMERS
- Publication
Molecules, 2024, Vol 29, Issue 1, p48
- ISSN
1420-3049
- Publication type
Article
- DOI
10.3390/molecules29010048