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The direct catalytic asymmetric aldol reaction has gained increasing
attention as an atom-economical proton-transfer C–C bond-forming process. In this
reaction, an active enolate is catalytically generated in situ and integrated into the
subsequent enantioselective addition to aldehydes. Recent advances in this field have
allowed for the implementation of various aldol donors in this efficient process,
however, those in the carboxylic acid oxidation state are yet to be exploited because
of the intrinsic difficulty of deprotonative activation.
The talk will mainly focus on thioamides as the aldol donor for the direct catalytic
asymmetric aldol reaction using soft Lewis acid/hard Brønsted base co-operative
catalyst system. Selective generation of enolate from thioamides through a soft-soft
interaction with soft Lewis acid favored selective (syn or anti) aldol reaction via
cyclic transition state with variety of α-branched and α-non-branched aldehydes. This
methodology offers selective aldol products in good chemical yield with high level of
ee. Also, divergent transformation of thioamide functionality and applications of this
methodology will be presented. |