Access to Planar Chiral Ferrocenes via N-Heterocyclic Carbene-Catalyzed Enantioselective Desymmetrization Reactions

Abstract

Ferrocene-derived dicarbaldehydes bearing pro-chiral planes are desymmetrized under the catalysis of chiral Nheterocyclic carbene organic catalysts. The reaction features selective activation and reaction of one of the aldehyde moieties of the ferrocene derivative while leaving the other aldehyde unit untouched. Our reaction affords enantiomerically enriched planar chiral ferrocene products obtained that are amenable for further transformations. Preliminary application studies show encouraging results when our products are explored for catalysis in chemical synthesis and for antimicrobial utilities in pesticide development.

N-Heterocyclic Carbene-Mediated Carbon–Sulfur Bond-Forming Reactions

“…53 The in situ-generated DABCO (1,4-diazabicyclo[2.2.2]-octane)/chiral phosphoric acid salt PA-I served as the effective proton shuttle and can give target thioester products 30 in excellent yields and optical purities. Very recently, Chi and co-workers 54 disclosed an NHC organocatalytic approach for the asymmetric synthesis of ferrocene-based planar chiral thioester 33 (Figure 7). A chiral NHC is solely used as the catalyst for this enantioselective desymmetrization of prochiral ferrocene dicarbaldehyde 31.…”

“…Very recently, Chi and co-workers disclosed an NHC organocatalytic approach for the asymmetric synthesis of ferrocene-based planar chiral thioester 33 (Figure ). A chiral NHC is solely used as the catalyst for this enantioselective desymmetrization of prochiral ferrocene dicarbaldehyde 31 .…”

Recent Advances in Chiral Aldehyde Catalysis for Asymmetric Functionalization of Amines

“…These chiral aldehydes, applied to the Michael addition/cyclization reaction of glycine-derived amides or dipeptides with chalcone 16a , generally exhibit better catalytic activity and enantioselectivity compared with the previous examples (Scheme 7c ). In addition, the groups of Tu, 22a Chi and Jin, 22b Zhang and Zheng, 22c Zhou, 22d e Xie, Wu, and Zhang, 22f and Xiao and Lu 22g have also designed novel chiral aldehyde catalysts using elegant synthetic methods.…”

N-Heterocyclic Carbene-Catalyzed Atroposelective Synthesis of N–N Axially Chiral 3-Amino Quinazolinones

“…In the last decade, a variety of structurally diverse C–C axially chiral biaryls and styrenes were demonstrated using carbene-catalyzed strategies involving kinetic resolutions, desymmetrizations, (benz)­annulations, central to axial chirality transfers, etc. by the groups of Zhao, Wang, Lupton, Zhu, Du, Ye, and Chi (Scheme a) . Moreover, NHCs are also useful for the atroposelective synthesis of C–N axially chiral compounds.…”