A new reaction of oximes and hydrazone derivatives using dinitrogen tetroxide under mild condition was found. The reaction of oximes and hydrazone derivatives with dinitrogen tetroxide in dry acetonitrile or tetrahydrofuran gave the corresponding carbonyl compounds respectively.
Dinitrogen tetroxide has been known to be self-ionized to $NO^+$ and $NO^-_3$ ion at low temperature in aprotic solvent. Dinitrogen tetroxide is the powerful nitrosating reagent at low temperature in acetonitrile or tetrahydrofuran. The reaction appears to proceed via the formation of N-nitroso intetermediate produced by nitrosation on the nitrogen atom of C=N.
We have found that some α-ketooximes reacted with dinitrogen tetroxide to give cyclic compounds of furoxan derivatives in excellent yields under mild conditions (0~ -40℃) in acetonitrile or tetrahydrofuran. The reaction appears to be initiated via the oxidation of oxime (C=NOH) to the nitrile oxide (CEN→0).
Thus, dinitrogen tetroxide is a good reagent for the deoximation and cyclization reaction under mild conditions.
Oxime 과 Hydrazone 은 Ketone 과 Aldehyde 의 Protecting group 으로써 많이 이용된다. 최근에는 이러한 Oxime 이나 Hydrazone 이 non-carbonyl compound 에서도 합성할 수 있으므로 Oxime과 Hydrazone 을 Ketone 이나 Aldehyde 로 변화시키는 것은 합성학적으로 중요한 의미를 가진다. 본인은 $N_2O_4$ 를 사용하여 니트로소화 반응을 이용하여 Hydrazone 이나 Oxime 을 쉽게 carbonyl compound 로 변화시켰다.
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또한 active methyl ketone과 $N_2O_4$ 를 반응시켜 biologically active cyclic compound 인 Furoxan 을 합성하였다.
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