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Direct stereoselective α-arylation of unmodified enals using an organocatalytic cross-coupling-like reaction.

Nature communications (2011-11-10)
Xixi Song, Aiguo Song, Fang Zhang, He-Xing Li, Wei Wang
ABSTRACT

Cross-coupling reactions typically rely on the use of transition metal catalysis. However, although achieving this process using metal-free organocatalysts is highly challenging, it could offer unique opportunities to discover novel bond-forming strategies in organic synthesis. Here we report a new amine catalysed direct stereoselective C-H α-arylation reaction of unmodified enals with bromoarenes. The power of this process, which involves an unprecedented iminium-Michael-alkylation-enamine-retro-Michael cascade sequence, has been demonstrated in the context of direct α-functionalization reactions of simple, unmodified enals with 4-bromophenols, 1-bromo-2-naphthol and 3-bromoindoles under mild reaction conditions. Notably, the process can be used for highly stereoselective syntheses of non-readily accessible E isomers, which normally require the use of transition metal-promoted cross-couplings and functionalized enals. The results of these studies significantly expand the scope of aminocatalysis.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
2-Naphthol, 99%
Sigma-Aldrich
2-Naphthol, 98%
Sigma-Aldrich
2-Naphthol, fluorescence indicator, ≥99.0%
Sigma-Aldrich
2-Naphthol, BioXtra, ≥99.0% (GC)