Squaramide-Catalyzed Synthesis of Enantioenriched Spirocyclic Oxindoles via Ketimine Intermediates with Multiple Active Sites.
A new method for the construction of five-membered spirocyclic oxindoles is based on a Michael-Mannich cascade reaction of a ketimine intermediated catalyzed by a bifunctional quinine-derived squaramide. The desired products were obtained in excellent yields (up to 94%) and stereoselectivities (up to >20:1 d.r., >99% ee). A scaled-up variant also proceeded smoothly showing that the one-pot reaction might find application in the synthesis of bioactive-compound libraries.
Department of Chemistry, Fudan University, 220 Handan Road, Shanghai 200433 (China).
Qiang-Sheng
QS
Sun
Department of Chemistry, Fudan University, 220 Handan Road, Shanghai 200433 (China).
Hua
H
Zhu
Department of Chemistry, Fudan University, 220 Handan Road, Shanghai 200433 (China).
Yong-Jian
YJ
Chen
Department of Chemistry, Fudan University, 220 Handan Road, Shanghai 200433 (China).
Xiao-Di
XD
Yang
Department of Chemistry, Fudan University, 220 Handan Road, Shanghai 200433 (China). sunxingwen@fudan.edu.cn.
Xing-Wen
XW
Sun
Shanghai Institute of Organic Chemistry, CAS, 354 Fenglin Road, Shanghai, 200032 (China).
Guo-Qiang
GQ
Lin
D002384:Catalysis; D020134:Catalytic Domain; D007097:Imines / Q000737:chemistry*; D007211:Indoles / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D009570:Nitriles / Q000737:chemistry*; D011803:Quinine / Q000031:analogs & derivatives* / Q000737:chemistry; D013141:Spiro Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
D007097:Imines; D007211:Indoles; D009570:Nitriles; D013141:Spiro Compounds; C542835:ketimine; C000609819:squaramide; D011803:Quinine
Mannich reactions; Michael additions; asymmetric synthesis; ketimines; nitrogen heterocycles; organocatalysis