title: Bifuctional amino-squaramides catalyzed asymmetric spiroannulation cascades with aliphatic β,γ-unsaturated α-keto esters: controlling an aldehyde enolate.
abstract: A quinidine-derived squaramide Ib catalyzed cyclization reaction of β-oxo aldehydes 1 and aliphatic or aromatic β,γ-unsaturated α-keto ester 2 is described. Using cyclic aldehyde substrates, this procedure provided a promising approach to a variety of spiro-3,4-dihydropyrans bearing three continuous quaternary and tertiary stereocenters in moderate to good yield with high stereoselectivities. Substituents on the nitrogen atoms of the squaramide moiety of the catalyst proved crucial to the reaction outcome. The stereochemistry of the three newly formed chiral centers (trans-selective) of the major product indicates a Micheal addition/hemiacetalization domino sequence for the present annulations.
authors.affiliation: Department of Chemistry, Zhejiang University, 20 Yugu Road, Hangzhou 310027, People's Republic of China.
authors.forename: Xiaoqin
authors.initials: X
authors.lastname: Wang
authors.forename: Weijun
authors.initials: W
authors.lastname: Yao
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Yao
authors.forename: Cheng
authors.initials: C
authors.lastname: Ma
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D000577:Amides / Q000737:chemistry*; D002384:Catalysis; D004952:Esters; D011714:Pyrans / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000447:Aldehydes; D000577:Amides; D004952:Esters; D011714:Pyrans