The Vinylogous Michael Addition of 3‐Alkylidene‐2‐oxindoles to β,γ‐Unsaturated α‐Keto Esters by Bifunctional Cinchona Alkaloids
作者:Manish K. Jaiswal、Rajesh Kumar、Sanjay Singh、Shailija Jain、Kumar Vanka、Ravi P. Singh
DOI:10.1002/ejoc.202000835
日期:2020.9.22
A highly enantioselective vinylogous Michaeladdition of 3‐alkylidene‐2‐oxindoles with β,γ‐unsaturated α‐keto esters using a bifunctional tertiary‐amine thiourea catalyst is demonstrated. The challenging Michael reaction with the β,γ‐unsaturated α‐keto esters has been accomplished due to the synchronized H‐bond guided dual activation of vinylogous nucleophile and electrophile by catalyst. The reaction
证明了使用双官能叔胺硫脲催化剂,对3-亚烷基-2-氧吲哚和β,γ-不饱和α-酮酯的高对映选择性乙烯基迈克尔加成反应。由于催化剂通过同步的H键引导对乙烯基亲核试剂和亲电试剂的双重活化,已经完成了与β,γ-不饱和α-酮酸酯的具有挑战性的迈克尔反应。该反应以高收率提供产物,同时导致优异的立体控制(高达99%ee和> 19:1 E / Z)。
HfCl<sub>4</sub>-Catalyzed [4 + 2] Cycloaddition of β,γ-Unsaturated α-Keto Esters with Alkynes
Herein we report Lewis acid HfCl4-catalyzed [4 + 2] cycloaddition between β,γ-unsaturated α-keto esters and various symmetric or unsymmetric alkynes, giving the desired polysubstituted 4H-pyrans in up to 98% yield and with excellent regioselectivity (>99:1) via a vinyl carbocation under mild conditions.
Switchable enantioselectivity was uncovered in the enantioselective catalytic conjugateaddition of β,γ-unsaturated α-keto esters with terminalalkynes to the chiral Lewis acid complex of In(BF4)3 and chiral phosphoric acid.