Significance:The authors report the coppercatalyzed decarboxylative propargylic alkylation of propargyl β-keto esters. Various β-ethynyl ketones were prepared in high yields (up to 96%) with excellent enantioselectivities (up to 98% ee).Comment: This work offers a new and facile access to a variety of β-ethynyl ketones with a new chiral ketimine P,N,N-ligand. Both the nucleophile and the electrophile are formed in situ. Therefore, the pregeneration of the enolate equivalents is not necessary. Cu(MeCN) 4 BF 4 (5 mol%) ligand (5.5 mol%) Proposed mechanism: Selected examples: R 1 O O 85% yield 86% ee O R 2 Et 3 N (1.2 equiv) PhMe, 0 °C, 12 h R 1 O R 2 N Ph N PPh 2 ligand Ph O Ph O Ph 96% yield 95% ee n-Pr O Ph MeO O Ph O 2 N 95% yield 93% ee 96% yield 94% ee Ph O O Ph 91% yield 95% ee S O Ph MeO 96% yield 98% ee 94% yield 97% ee O

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