Cobalt(II)-Catalyzed Enantioselective Propargyl Claisen Rearrangement: Access to Allenyl-Substituted Quaternary β-Ketoesters.
Ya-Ping WangXing-Ping ZhangMing-Sheng XieHai-Ming GuoPublished in: Organic letters (2023)
Highly enantioselective propargyl Claisen rearrangement of O -propargyl β-ketoesters was achieved under 2.5 mol % of the chiral cobalt complex as the catalyst under mild reaction conditions. With Co(OTf) 2 as the Lewis acid and C 1 -symmetric imidazoline-pyrroloimidazolone pyridine as the ligand, diverse chiral allenyl-substituted all-carbon quaternary β-ketoesters were obtained in good yields (up to 97% yield) and high enantioselectivities (up to 98% ee).