Dibenzoylfuroxan 3 (R = Ph) reacts with hydroxylamine in a ring transformation to give a 4,5dioximino-3-phenyl-l,2-oxazole 6. The structure of 6 has been confirmed by an X-ray structure determination. Some density functional theoretical (DFT) calculations for 6 and related compounds are reported.On the interaction of 3,4-dibenzoylfuroxan with hydroxyknnine the interaction of acetic anhydride with 4-phenylfuroxan (7) or with a-hydroximinophenyiacetonitriloxide (4) as well as the interaction of the diacetyl derivative of phenylchloroglvoxime with sodium carbonate (3b) which produce a lowmelting isomer of 1_(R = Ph).
Preparative InvestigationsWe believed the oximation of dibenzoylfiiroxan to be the superior method because of the well known reactivity of aldehydes and ketones in the furoxan series (la). Unfortunately, our attempts to reproduce this synthesis (5) failed.When conducting the oximation of dibenzoylfuroxan in ethanol in the presence of small amounts of water, a substance with mp 172-175°C was obtained. The same compound was formed when the oximation was carried out in 2-propanol. pyridine or dimethylformamide. According to both the mass spectrum (m/: = 205) and to lj C NMR (7 signals) this compound is not a dioxime of 3,4-dibenzoylfuroxan. The structure was solved unambigously by an X-ray diffraction analysis (8), which showed that a 4,5-dioximino-3-phenyl-l,2-oxazole 6 has been formed. It is interesting to note that in the solid state 3 molecules of 6 are connected via linear and bifurcated hydrogen bonds (Fig.l, see Theoretical
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