Enantioselective Formal Vinylogous N–H Insertion of Secondary Aliphatic Amines Catalyzed by a High-Spin Cobalt(II) Complex

Abstract

Vinylcarbene insertion into the nitrogen–hydrogen (N–H) bond of amines allows direct access to α,β-unsaturated γ-amino acid derivatives, meeting a marked challenge in the control of regio- and enantioselectivities. Here, we report a highly γ-selective and enantioselective insertion into N–H bonds of aliphatic or aromatic secondary amines with vinyl substituted α-diazo pyrazoleamides using a high-spin chiral N,N′-dioxide/cobalt­(II) complex catalyst. The method affords a wide variety of valuable optically active Z- and E-type vinyl γ-amino amides. Calculation reveals a spin state change from the quartet cobalt­(II) complex to a doublet Co­(II)-carbene species for facile Z-selective and enantioselective nucleophilic addition.

Asymmetric Catalytic (2+1) Cycloaddition of Thioketones to Synthesize Tetrasubstituted Thiiranes

“…Firstly, the diazo bound Co II intermediate Int1 was considered as a reactive species for the following investigations [10g, 11] . We examined two pathways by which the release of N 2 possibly takes place through either doublet or quartet transition state [11e] . The results show that the quartet state pathway is much more favorable than the doublet pathway, yielding a spin crossover product Co(ΙΙ) carbene species Int2 D .…”

Enantioselective Synthesis of Nitriles Containing a Quaternary Carbon Center by Michael Reactions of Silyl Ketene Imines with 1-Acrylpyrazoles

“…DFT calculations were performed using Gaussian software (see the Supporting Information for more details). Previously, we showed that a 1-acrylpyrazole-bound Co­(II) complex is a stable species . As such, the complex Int1 was considered as a reactive species for the SKI addition (Figure ).…”

Catalysts Based on the C−H⋅⋅⋅M Weak Interaction: Synthesis, Characterization and Catalytic Application of Bis(pyrazolyl)borate Cu(I) Complexes in Carbene Insertion into Heteroatom Hydrogen Bonds

“…The catalytic carbene insertion into NÀ H bonds has attracted much attention because it provides various bioactive molecules such as α-amino acid derivatives and α-amino ketones. [3,13] Our investigations on the catalytic application of complexes IV-VIII were started on carbenoid NÀ H insertions by using αdiazoacetate 1 a and aniline 2 a at room temperature with 2 mol% of catalyst (Table 1). The catalytic carbenoid NÀ H insertions by complexes IV-VIII all worked well, with VI demonstrating the highest catalytic activity (entries 1-5).…”

“…Transition-meta-catalyzed carbene migratory insertion into CÀ H or XÀ H bonds is a powerful tool for the construction of CÀ C and CÀ X bonds. [1] In the past few years, many types of XÀ H insertions including OÀ H, [2] NÀ H, [3] SÀ H, [4] SiÀ H [5] and recently emerged BÀ H [6] bonds have been realized with different carbene precursors [7] and catalysts. Despite much progress have been made in this type of reaction, in view of its great utility and wide application, the development of new highly efficient and selective catalysts is still in demand.…”