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Reaction of pyrylium salts with nucleophiles. Part 25. Formation of pyridine-1-oxides, 2-isoxazolines and 1-pyrazoline-1-oxides

✍ Scribed by Cornelia Uncuta; Miron Teodor Cǎproiu; Valentin Câmpeanu; Aurica Petride; Mariana G Dǎnilǎ; Marieta Plǎveti; Alexandru T Balaban

Publisher
Elsevier Science
Year
1998
Tongue
French
Weight
989 KB
Volume
54
Category
Article
ISSN
0040-4020

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✦ Synopsis

The reaction of tri-and tetrasubstituted pyrylium salts with hydroxylamine affords acyclic keto-ketoximes (to be described in a separate paper) which cyclize yielding pyridine-l-oxides and/or 2-isoxazolines. Both these classes of compounds, with many possible applications, can thus be obtained simply and in good yield. The regioselectivity of 2-isoxazoline formation from unsymetrically substituted pyrylium salts is discussed. An unprecedented minor product formed from 2,6-di-t-butyl-4-methylpyrylium perchlorate and two molecules of hydroxylarnine is the corresponding I-pyrazoline-l-oxide. Mechanistic rationalization of all products are provided.

📜 SIMILAR VOLUMES

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