Ring-opening and recyclization of 3,4-diacylfuroxans by nitrogen nucleophiles

Interaction of 3,4-diacylfuroxans with hydroxylamine hydrochloride results in the formation of substituted 4,5-bis (hydroximino)-4,5-dihydroisoxazoles, whereas the reaction of 3,4-bis(4-methylfurazanoyl-3)furoxan with hydrazine hydrate in acetic acid affords 3-[4,5-bis(hydroximino)-4,5-dihydro-1H-pyrazol-3-yl]-4-methylfurazan. N-Acyl-, N-nitro-, N-alkyl- and N-adamantyl derivatives of the latter compound have been synthesized. X-Ray structure determinations together with density functional theoretical calculations are reported.