Abstract
Asymmetric decarboxylative Mannich addition of β‐keto acids or malonic acid half‐esters to β,γ‐alkynyl‐α‐ketimino esters catalyzed by cinchona alkaloid‐derived squaramide has been developed. The reaction proceeded by forming a nucleophilic enolate after decarboxylation, followed by its addition to β,γ‐alkynyl‐α‐ketimino esters facilitated by the bifunctional catalyst. A broad range of substrates with various substituents are tolerated in this reaction, yielding a series of α,α‐disubstituted amino acid derivatives bearing alkynyl functional groups in high yields with good to excellent enantioselectivities. The practicality of this method was demonstrated by a gram‐scale reaction and subsequent elaboration of the Mannich adducts.
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