title: Temperature-dependent annuloselectivity and stereochemistry in the reactions of methanesulfonyl sulfene with imines.
abstract: The annuloselectivity in the reactions of methanesulfonyl sulfene and imines varies with temperature. At a relatively higher temperature of 20 °C, the [2(s) + 2(i)] annulation of different N-alkyl imines occurs exclusively, giving four-membered trans-β-sultams in up to 69% yields. At a lower temperature of -78 °C, the [2(s) + 2(i) + 2(i)] annulation of N-methyl imines takes place specifically, delivering six-membered 1,2,4-thiadiazine 1,1-dioxides, 4-aza-δ-sultams, in up to 80% yields, with diverse configurations at the C3, C5, and C6 stereocenters. The trans-stereochemistry involved in the [2(s) + 2(i)] annulations is attributed to the conrotatory ring closure of the thermodynamically stable 2,3-thiazabutadiene-type zwitterionic intermediates, while the diverse stereochemical outcomes in the [2(s) + 2(i) + 2(i)] annulations are caused by the iminium isomerization in the stepwise nucleophilic [4 + 2] annulation between the same zwitterionic intermediates and a second molecule of N-methyl imines.
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. zhyang@mail.buct.edu.cn jxxu@mail.buct.edu.cn.
authors.forename: Qiuyue
authors.initials: Q
authors.lastname: Wu
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. zhyang@mail.buct.edu.cn jxxu@mail.buct.edu.cn.
authors.forename: Zhanhui
authors.initials: Z
authors.lastname: Yang
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. zhyang@mail.buct.edu.cn jxxu@mail.buct.edu.cn.
authors.forename: Jiaxi
authors.initials: J
authors.lastname: Xu