The Nucleophilic Reaction Of Benzylic C-H Bond Of Azaarenes With N=O Bonds

In recent years, nitroso compounds have been widely used to react with virious unsaturated compounds such as dienes, alkenes, alkynes, aldehydes and α,β-unsaturated ester via nucleophilic addition or cycloaddition reactions. However, to the best of our knowledge, no precedent on nucleophilic addition of benzylic C-H bond to nitroso compounds (N=O bonds) was reported. Combining the interest of our research group in nucleophilic reaction of benzylic C-H bonds, we studied the nucleophilic addition of benzylic C-H bond with nitroso compounds.This paper is divided into two parts. In the first part, the nucleophilic addition of benzylic C-H bond with nitrosobenzene was studied. With the reaction of 2-methylquinoline with p-chloronitrosobenzene as the model reaction, systematic optimization was carried out to establish the best reaction conditions as:catalyzed by p-nitrobenzoic acid in dry dimethyl sulfoxide under argon atmosphere at room temperature to afford the nucleophilic addition-dehydration aldimine products. Interestingly, when the reaction of 2-methylquinoline and the p-chloronitrosobenzene were catalyzed by the more acidic p-toluenesulfonic acid (p-TSA), the quinoline-2-carbaldehyde was isolated as the main product due to the further hydolysis.Encouraged by the exciting results obtained between the nucleophilic additions of alkylazaarenes to substituted nitrosobenzenes, the application of this reaction to tert-butylnitrite (tBuONO) was investigated next. The nucleophilic addition product was found to be oxime, but not the anticipated dehydration product, maybe due to their different thermodynamics stabilities.