title: Base-switched annuloselectivity in the reactions of ethyl malonyl chloride and imines.
abstract: The base-switched annuloselectivity, namely [2 + 2] and [2 + 2 + 2] selectivity, in the reactions of ethyl malonyl chloride and imines is successfully realized. In the presence of the weak nucleophilic base 2-chloropyridine, the reactions deliver ethyl trans-β-lactam-3-carboxylates as the exclusive [2 + 2] products in up to 93% yields, while with the strong nucleophilic N-methylimidazole as the base, the reactions give rise to 2,3-dihydro-1,3-oxazin-4-one derivatives as the sole products in up to 99% yields via the formal [2 + 2 + 2] cycloaddition involving one molecule of the imine and two molecules of the ketene generated from malonyl chloride. Notably, ethyl trans-β-lactam-3-carboxylates are synthesized for the first time directly from the reactions of ethyl malonyl chloride and imines. Mechanistic discussions reveal that the annuloselectivity is controlled by the nucleophilicity of organic bases.
authors.affiliation: State Key Laboratory of Chemical Resource Engineering, Department of Organic Chemistry, Faculty of Science, Beijing University of Chemical Technology, Beijing 100029, P. R. China. jxxu@mail.buct.edu.cn.
authors.forename: Zhanhui
authors.initials: Z
authors.lastname: Yang
authors.forename: Siqi
authors.initials: S
authors.lastname: Li
authors.forename: Zhong
authors.initials: Z
authors.lastname: Zhang
authors.forename: Jiaxi
authors.initials: J
authors.lastname: Xu
mesh_terms: D048588:Benzoxazines / Q000138:chemical synthesis* / Q000737:chemistry; D002264:Carboxylic Acids / Q000138:chemical synthesis* / Q000737:chemistry; D003500:Cyclization; D007097:Imines / Q000737:chemistry*; D008314:Malonates / Q000737:chemistry*; D015394:Molecular Structure
chemical_list: D048588:Benzoxazines; D002264:Carboxylic Acids; D007097:Imines; D008314:Malonates; C000599267:ethyl malonyl chloride