title: Amine-catalyzed tunable reactions of allenoates with dithioesters: formal [4+2] and [2+2] cycloadditions for the synthesis of 2,3-dihydro-1,4-oxathiines and enantioenriched thietanes.
abstract: The chemoselective [4+2] vs. [2+2] cycloaddition between allenoates and dithioesters can be controlled by switching the nucleophilic amine catalyst. The two modes of cyclizations represent the first example of controllable and chemoselective annulations between allenoates and dienophiles catalyzed by amine. These cyclizations are useful in offering a divergent synthesis of sulfur-containing heterocycles. On the basis of this investigation, it can be realized that dithioesters with a vicinal electron-withdrawing group can react not only like a Michael acceptor but also as a ketone or imine.
authors.affiliation: State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, P. R. China. weiyin@mail.sioc.ac.cn mshi@mail.sioc.ac.cn.
authors.forename: Hai-Bin
authors.initials: HB
authors.lastname: Yang
authors.forename: Yu-Chao
authors.initials: YC
authors.lastname: Yuan
authors.forename: Yin
authors.initials: Y
authors.lastname: Wei
authors.forename: Min
authors.initials: M
authors.lastname: Shi