Benzonitrile from benzaldoxime

Typical procedure. Benzonitrile from benzaldoxime [1139] Anhydrous aluminum chloride (0.264 g, 2 mmol) and sodium iodide (0.900 g, 6 mmol) were added to dry acetonitrile (25 mL) and the mixture was stirred magnetically for 0.5 h at room temperature under nitrogen. Benzaldoxime (0.121 g, 1 mmol) was added and stirring was continued under reflux for a further 2.5 h. The progress of the reaction was monitored by TLC. The reaction mixture was subsequently poured into ice-cold 10% aq. ammonia solution and extracted with diethyl ether. The combined organic layers were washed with water (2 x 100 mL), dried, and the solvent was distilled off under reduced pressure to give benzonitrile 0.098 g, 95% yield. 

Bernhart, C. and C.G. Wermuth. 1977. Benzonitriles from benzaldoximes and enamine. Synthesis 5 338-339. 

Benzonitrile oxide (C in Figure 15.44) is an isolable 1,3-dipole. It can be generated from benzaldoxime and anNaOH/Cl2 solution. Under these reaction conditions the oxime/nitroso anion (A B) is initially formed and chlorine disproportionates into Cl—O and chloride. An SN reaction of the negatively charged C atom of the anion A B at the Cl atom of Cl— O or of Cl—O—H affords the oc-chlorinated nitroso compound E, which tautomerizes to the hydroxamic acid chloride D. From that species, the nitrile oxide C is generated via a base mediated 1,3-elimination. Isoxazoles are formed in the reactions of C with alkynes (Figure 15.44), while isoxazolines would be formed in its reactions with alkenes. 

However, from benzaldoxime and phenylcarbonimidoyl dichlorides a mixture of phenyl isocyanate, benzonitrile, and aniline hydrochloride is obtained. 

Scholl and co-workers reported that mercury cyanate (fulminate) and HCI reacts with benzene in the presence of AICI3 to give benzaldoxime and benzonitrile, whereas the aldoxime of resorcinol and by-product dioxybenzonitrile is produced from the same reagents but in the absence of AICI3 (Eq 1.20). 

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