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DOI: 10.1055/s-0034-1378501
Organocatalytic Atroposelective Synthesis of Axially Chiral Biaryls
Publication History
Publication Date:
18 July 2014 (online)
Significance
Sparr and co-worker report an organocatalytic atroposelective aldol condensationto access axially chiral biaryl compounds. Using 5 mol% of amine catalyst 1, the desired products can be obtained in good to high yields and enantioselectivities.
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Comment
Axially chiral compounds are interesting scaffolds and play an important role in drug discovery and catalysis. The authors developed a new strategy to access these molecules atroposelectively, applying an intramolecular condensation reaction (for a related enol-exo aldol reaction, see B. List et al. Angew. Chem. Int. Ed 2003, 42, 2785). In the first step of this transformation, the α-carbon atom is activated by a dienamine formation between catalyst 1 and the aldehyde. Due to the Z-geometry of the olefin and the ortho disubstitution, the α-carbon atom is positioned over the keto function in the molecule after rotation. This allows a transfer of the stereochemistry from the catalyst to the axial chirality of the biaryl compounds during the intramolecular aldol addition. In the final dehydration step, the desired products are irreversibly generated by arene formation. A possible transition-state model (A) for the aldol addition step is proposed here.
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