Enantioselective thiourea-catalyzed additions to oxocarbenium ions.
Asymmetric, catalytic reactions of oxocarbenium ions are reported. Simple, chiral urea and thiourea derivatives are shown to catalyze the enantioselective substitution of silyl ketene acetals onto 1-chloroisochromans. A mechanism involving anion binding by the chiral catalyst to generate a reactive oxocarbenium ion is invoked. Catalysts bearing tertiary benzylic amide groups afforded highest enantioselectivities, with the optimal structure being derived from enantioenriched 2-arylpyrrolidine derivatives.
Reisman
Sarah E
SE
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Doyle
Abigail G
AG
Jacobsen
Eric N
EN
D000080:Acetals / Q000737:chemistry*; D002384:Catalysis; D002839:Chromans / Q000138:chemical synthesis / Q000737:chemistry*; D013237:Stereoisomerism; D013890:Thiourea / Q000737:chemistry*
D000080:Acetals; D002839:Chromans; D013890:Thiourea