title: Direct catalytic asymmetric Mannich-type reactions of gamma-butenolides: effectiveness of Brønsted acid in chiral metal catalysis.
abstract: Direct catalytic asymmetric Mannich-type reactions of gamma-butenolides are described. A chiral Lewis acid/amine base/Brønsted acid combination was used to catalyze a gamma-addition of gamma-butenolides to N-diphenylphosphinoyl imines, affording the products in up to >99% yield, anti/syn = >97:3, and 84% ee. The use of a catalytic amount of TfOH in addition to La(OTf)3/Me-PyBox/TMEDA was important for improving yield and stereoselectivity.
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Tokyo, Japan.
authors.forename: Akitake
authors.initials: A
authors.lastname: Yamaguchi
authors.forename: Shigeki
authors.initials: S
authors.lastname: Matsunaga
authors.forename: Masakatsu
authors.initials: M
authors.lastname: Shibasaki
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000737:chemistry; D000143:Acids / Q000737:chemistry; D002384:Catalysis; D007097:Imines / Q000737:chemistry; D008352:Mannich Bases / Q000737:chemistry; D008670:Metals / Q000737:chemistry*; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D000143:Acids; D007097:Imines; D008352:Mannich Bases; D008670:Metals; C004511:butenolide; D015107:4-Butyrolactone