Organocatalytic intramolecular (4 + 2) annulation of enals with ynamides: atroposelective synthesis of axially chiral 7-aryl indolines

Catalytic enantioselective transformation of alkynes has become a powerful tool for the synthesis of axially chiral molecules. Most of these atroposelective reactions of alkynes rely on transition-metal catalysis, and the organocatalytic approaches are largely limited to special alkynes which act as...

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Published in:Chemical science (Cambridge) 2023-06, Vol.14 (22), p.5918-5924
Main Authors: Zhang, Zhi-Xin, Liu, Li-Gao, Liu, Yi-Xi, Lin, Jian, Lu, Xin, Ye, Long-Wu, Zhou, Bo
Format: Article
Language:English
Subjects:
Alkynes
Aromatic compounds
Catalysis
Chemical reactions
Chemical synthesis
Chemistry
Enantiomers
Heterocyclic compounds
Organic chemistry
Phosphines
Regioselectivity
Transition metals
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Summary:Catalytic enantioselective transformation of alkynes has become a powerful tool for the synthesis of axially chiral molecules. Most of these atroposelective reactions of alkynes rely on transition-metal catalysis, and the organocatalytic approaches are largely limited to special alkynes which act as the precursors of Michael acceptors. Herein, we disclose an organocatalytic atroposelective intramolecular (4 + 2) annulation of enals with ynamides. This method allows the efficient and highly atom-economical preparation of various axially chiral 7-aryl indolines in generally moderate to good yields with good to excellent enantioselectivities. Computational studies were carried out to elucidate the origins of regioselectivity and enantioselectivity. Furthermore, a chiral phosphine ligand derived from the synthesized axially chiral 7-aryl indoline was proven to be potentially applicable to asymmetric catalysis. An organocatalytic intramolecular (4 + 2) annulation of enals with ynamides is disclosed, providing a convenient way to axially chiral indolines. The synthesized axially chiral skeleton was proved to be potentially applicable as a chiral ligand.
ISSN:2041-6520
2041-6539
DOI:10.1039/d3sc01880f