Organocatalytic asymmetric arylation of indoles enabled by azo groups.

Autor: Qi LW; Department of Chemistry, South University of Science and Technology of China, Shenzhen 518055, China., Mao JH; Department of Chemistry, South University of Science and Technology of China, Shenzhen 518055, China., Zhang J; Department of Chemistry, South University of Science and Technology of China, Shenzhen 518055, China., Tan B; Department of Chemistry, South University of Science and Technology of China, Shenzhen 518055, China.
Jazyk: angličtina
Zdroj: Nature chemistry [Nat Chem] 2018 Jan; Vol. 10 (1), pp. 58-64. Date of Electronic Publication: 2017 Oct 02.
DOI: 10.1038/nchem.2866
Abstrakt: Arylation is a fundamental reaction that can be mostly fulfilled by electrophilic aromatic substitution and transition-metal-catalysed aryl functionalization. Although the azo group has been used as a directing group for many transformations via transition-metal-catalysed aryl carbon-hydrogen (C-H) bond activation, there remain significant unmet challenges in organocatalytic arylation. Here, we show that the azo group can effectively act as both a directing and activating group for organocatalytic asymmetric arylation of indoles via formal nucleophilic aromatic substitution of azobenzene derivatives. Thus, a wide range of axially chiral arylindoles have been achieved in good yields with excellent enantioselectivities by utilizing chiral phosphoric acid as catalyst. Furthermore, highly enantioenriched pyrroloindoles bearing two contiguous quaternary chiral centres have also been obtained via a cascade enantioselective formal nucleophilic aromatic substitution-cyclization process. This strategy should be useful in other related research fields and will open new avenues for organocatalytic asymmetric aryl functionalization.
Databáze: MEDLINE
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