A Highly Efficient Method for the Synthesis of Nitrogen-containing Materials Using Umpolung Addition to Electron-Deficient Imines

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We have already reported that the N-alkylation reaction of alpha-iminoester proceeds using aluminum reagents to give the N-alkylation products in high yields. In the present project, we investigated highly regioselective N-alkylation of beta,gamma-alkenyl-alpha-iminoesters and subsequent directed vinylogous aldol reaction with in situ generated dienolates. It was also found that the sulfenyl group of the alkene part improved the selectivity of both steps, leading to the formation of 3-amino-2-pyrones by anti-elimination of thiols. Furthermore, on treatment with two different Grignard reagents, alpha-acyloxyimino esters gave the corresponding dialkylation products with different substituents on the nitrogen atom. N,N,C-Trialkylated products with all different substituents were obtained via the oxidation and the nucleophilic addition reaction to the resulting iminium salts.