Chiral Squaramides as Highly Enantioselective Catalysts for Michael Addition Reactions of 4-Hydroxycoumarins and 4-Hydroxypyrone to β,γ-Unsaturated α-Keto Esters
Distance brings forth beauty: The first highlyenantioselectiveorganocatalyticMichaeladdition of 4‐hydroxycoumarins and the analogous 4‐hydroxy‐6‐methyl‐2‐pyrone to β,γ‐unsaturated α‐keto esters by using chiral squaramides as the organocatalysts is disclosed. The efficiency of the process is attributed to the hydrogen‐bonding activation (see scheme).
motifs in organocatalysis, whereas efficient 1,3‐diamine‐derived organocatalysts are very rare. Herein we report a highly efficient camphor‐1,3‐diamine‐derived squaramideorganocatalyst. Its catalytic activity in Michaeladditions of 1,3‐dicarbonyl nucleophiles to trans‐β‐nitrostyrene derivatives provides excellent enantioselectivities (up to >99% ee).
Organocatalytic asymmetric conjugate addition of cyclic 1,3-dicarbonyl compounds to β,γ-unsaturated α-ketoesters
作者:Jin-jia Wang、Jin-hua Lao、Zhi-peng Hu、Rui-Jiong Lu、Shao-zhen Nie、Quan-sheng Du、Ming Yan
DOI:10.3998/ark.5550190.0011.922
日期:——
The conjugateaddition of cyclic1,3-dicarbonylcompounds to β,γ-unsaturated α-keto-esters was studied using a series of chiral bifunctional organocatalysts. Takemoto’s catalyst was found to be most efficient for this transformation. Excellent yields and good enantioselectivities were achieved for a variety of β,γ-unsaturated α-keto-esters and cyclic1,3-dicarbonylcompounds. A bifunctional catalytic