The title compound (Ac+OH) was synthesized for the purpose of developing a new NAD+ model compound which is capable of oxidizing alcohols and amines. The absorption spectrum of Ac+OH was similar to that of N-methylacridinium ion (Ac+) in the acidic pH region and to that of 5-deazaflavin in the basic pH region. The absorption spectrum of the reduced form was analogous to that of 3-aminophenol. The reduced form which was prepared by NaBH4 reduction was promptly reoxidized by molecular oxygen. With the aid of potassium tert-butoxide, Ac+OH oxidized benzyl alcohol and cyclohexanol to the corresponding aldehyde and ketone in almost quantitative yields. In contrast, Ac+ was totally useless as an oxidant under the same reaction conditions. Benzylamine was oxidized by Ac+ to benzaldehyde in low yields (11-24%). On the other hand, the oxidation by Ac+OH occurred in good yields (82-88%). When the reaction was carried out under an oxygen stream, the yield calculated on the basis of Ac+OH was enhanced up to 1800-2200%. The results indicate that Ac+OH acts as an effective turnover oxidizing agent and that the 3-hydroxyl group plays a crucial role in the redox reactions occurring on the acridinium nucleus. This is the first example of the facile oxidation of alcohols and amines which mimics the catalytic behavior of NAD+ coenzyme.
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