Preparation of isoxazole pyrazole and isothiazole
Isoxazole and pyrazole synthesis While 1,3-diketones undergo condensation with hydroxylamine to produce isoxazoles, with hydrazine they yield corresponding pyrazoles.
Isothiazole synthesis Isothiazole can be prepared from thioamide in the following way.
Reactions of isoxazole, pyrazole and isothiazole
Like 1,3-azoles, due to the presence of a pyridine-like nitrogen atom in the ring, 1,2-azoles are also much less reactive towards electrophilic substitutions than furan, pyrrole or thiophene. However, 1,2-azoles undergo elec-trophilic substitutions under appropriate reaction conditions, and the main substitution takes place at the C-4 position, for example bromination of 1,2-azoles. Nitration and sulphonation of 1,2-azoles can also be carried out, but only under vigorous reaction conditions.
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