The enantioselective construction of quaternary carbon centers is a marked challenge in asymmetric catalysis research. It is extremely difficult when a chiral catalyst can not distinguish the facial selectivity of the substrate through bond interactions. Here we realized an enantioselective Michael reaction of silyl ketene imines to 1-acrylpyrazoles using a chiral N,N′-dioxide−Co(II) complex. The protocol is highly efficient for the construction of nitrile-, aryl-, and dialkyl-bearing carbon centers and has been successful applied in the divergent synthesis of pharmaceuticals and natural products. The through-space dispersion interactions between unbound silyl ketene imines and the 1-acrylpyrazole-bonded catalyst play a key role in facilitating the reactivity and the enantioselectivity of this process.

The enantioselective [3 + 1]-cycloaddition of racemic donor–acceptor (D–A) aziridines with isocyanides was first realized under mild reaction conditions using a chiral N,N′-dioxide/MgII complex as catalyst, providing a facile route to enantioenriched exo-imido azetidines with good to excellent yield (up to 99%) and enantioselectivity (up to 94% ee). An obvious chiral amplification effect was observed in this system, and an explanation was elucidated based on the experimental investigation and X-ray crystal structure of the enantiomerically pure catalyst.

Herein, we report the first example of enantioselective (2+1) cycloaddition of thioketones with α-diazo pyrazoleamides for the direct synthesis of tetrasubstituted thiiranes. In the presence of chiral N,N'dioxide/cobalt(ΙΙ) complexes (2-5 mol%), excellent efficiency (up to 99 % yield within 15 mins) and high stereoselectivity (up to > 19 : 1 dr and 97 % ee) are available. Elaborations of thiiranes via desulfuration have also been conducted to deliver tetrasubstituted olefins. Density functional theory calculations reveal that the reaction initiates from a doublet state cobalt(ΙΙ) carbenoid, which is followed by a quartet cobalt(ΙΙ)bound thiocarbonyl ylide pathway. This work provides a route for the selective construction of tetrasubstituted thiiranes and olefins that are otherwise difficult to access.

Herein, we report the first example of enantioselective (2+1) cycloaddition of thioketones with α‐diazo pyrazoleamides for the direct synthesis of tetrasubstituted thiiranes. In the presence of chiral N,N′‐dioxide/cobalt(ΙΙ) complexes (2–5 mol%), excellent efficiency (up to 99 % yield within 15 mins) and high stereoselectivity (up to >19 : 1 dr and 97 % ee) are available. Elaborations of thiiranes via desulfuration have also been conducted to deliver tetrasubstituted olefins. Density functional theory calculations reveal that the reaction initiates from a doublet state cobalt(ΙΙ) carbenoid, which is followed by a quartet cobalt(ΙΙ)‐bound thiocarbonyl ylide pathway. This work provides a route for the selective construction of tetrasubstituted thiiranes and olefins that are otherwise difficult to access.

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