Quinidine derived organocatalysts for the nucleophile promoted asymmetric [4+2] cycloaddition reaction of salicyl N-tosylimine with allenic esters
作者:Cheng-Kui Pei、Min Shi
DOI:10.1016/j.tetasy.2011.06.030
日期:2011.6
Cinchona alkaloid derived catalyst cat. 5 prepared fromβ-isocupreidine (β-ICD) was found to be a fairly effective organocatalyst for the nucleophilic promoted asymmetric [4+2] cycloaddition reaction of salicyl N-tosylimines and allenic esters to give the corresponding adducts in up to 80% yield, 87% ee.
A chemo- and enantioselective [3 + 2] annulation of Morita–Baylis–Hillmancarbonates of isatins with propargyl sulfones was catalyzed by a β-ICD O-MOM ether 1c, affording spirocyclic 2-oxindoles bearing an unusual cyclopentadiene motif in outstanding ee values (up to >99%). More electrophiles, such as N-phenylmaleimide, have been also utilized to deliver complex spirocyclic 2-oxindoles with good results