title: Asymmetric [3 + 2] Cycloaddition of Chiral N-Phosphonyl Imines with Methyl Isocyanoacetate for Accessing 2-Imidazolines with Switchable Stereoselectivity.
abstract: Asymmetric [3 + 2] cycloaddition of chiral N-phosphonyl imines with methyl isocyanoacetate has been established, enabling controllable/switchable stereoselectivity access to 21 examples of cycloadducts with good to excellent chemical yields (up to 92%) and high diastereoselectivities (up to 99:1 dr). The cycloaddition reaction promoted by Cs2CO3resulted in diastereoenriched (4R,5S)-products with >99:1 dr. However, it showed the reverse stereoselectivity as diastereoenriched (4S,5R) products when AgF was employed as the catalyst. The synthesis followed the group-assisted purification (GAP) chemistry/technology in which the pure 2-imidazoline products were readily provided by washing the crude products with cosolvents of hexane and ethyl acetate.
authors.affiliation: Department of Chemistry and Biochemistry, Texas Tech University , Lubbock, Texas 79409-1061, United States.
authors.forename: Shuo
authors.initials: S
authors.lastname: Qiao
authors.affiliation: Department of Chemistry and Biochemistry, Texas Tech University , Lubbock, Texas 79409-1061, United States.
authors.forename: Cody B
authors.initials: CB
authors.lastname: Wilcox
authors.affiliation: Department of Chemistry and Biochemistry, Texas Tech University , Lubbock, Texas 79409-1061, United States.
authors.forename: Daniel K
authors.initials: DK
authors.lastname: Unruh
authors.affiliation: Department of Chemistry and Biochemistry, Texas Tech University , Lubbock, Texas 79409-1061, United States.|School of Chemistry and Materials Science, Jiangsu Normal University , Xuzhou 221116, P. R. China.
authors.forename: Bo
authors.identifier: 0000-0003-3878-515X
authors.initials: B
authors.lastname: Jiang
authors.affiliation: Department of Chemistry and Biochemistry, Texas Tech University , Lubbock, Texas 79409-1061, United States.|Institute of Chemistry and BioMedical Sciences and School of Chemistry and Chemical Engineering, Nanjing University , Nanjing 210093, P. R. China.
authors.forename: Guigen
authors.identifier: 0000-0002-9312-412X
authors.initials: G
authors.lastname: Li
mesh_terms: D002384:Catalysis; D061565:Cycloaddition Reaction; D048288:Imidazolines / Q000737:chemistry*; D007097:Imines / Q000737:chemistry*; D017953:Isocyanates / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods; D013237:Stereoisomerism
chemical_list: D048288:Imidazolines; D007097:Imines; D017953:Isocyanates