title: BOROX catalysis: self-assembled amino-BOROX and imino-BOROX chiral Brønsted acids in a five component catalyst assembly/catalytic asymmetric aziridination.
abstract: A five-component catalyst assembly/aziridination reaction is described starting from an aldehyde, an amine, ethyl diazoacetate, B(OPh)(3), and a molecule of a vaulted biaryl ligand (VAPOL or VANOL). A remarkable level of chemo-selectivity was observed since, while 10 different products could have resulted from various reactions between the five components, an aziridine was formed in 85% yield and 98% ee and only two other products could be detected in 3% yield. Studies reveal that the first in a sequence of three reactions is an exceedingly rapid amine-induced assembly of an amino-BOROX chiral Brønsted acid species from VAPOL and B(OPh)(3), which is followed by imine formation from the amine and aldehyde and the concomitant formation of an imino-BOROX chiral Brønsted acid and finally the reaction of the imine with ethyl diazoacetate mediated by the imino-BOROX catalyst to give aziridine-2-carboxylic esters with very high diastereo- and enantioselectivity.
authors.affiliation: Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Anil K
authors.initials: AK
authors.lastname: Gupta
authors.forename: Munmun
authors.initials: M
authors.lastname: Mukherjee
authors.forename: Gang
authors.initials: G
authors.lastname: Hu
authors.forename: William D
authors.initials: WD
authors.lastname: Wulff
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D000588:Amines / Q000737:chemistry*; D001388:Aziridines / Q000737:chemistry*; D001896:Boron Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D002384:Catalysis; D007097:Imines / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000447:Aldehydes; D000588:Amines; D001388:Aziridines; D001896:Boron Compounds; D007097:Imines; D008024:Ligands; D009942:Organometallic Compounds; C033132:aziridine