Asymmetric cycloadditions of o-quinone methides employing chiral ammonium fluoride precatalysts.
The catalytic, enantioselective, [4 + 2] cycloaddition reaction of ortho-quinone methides with silyl ketene acetals is described. This mechanistically interesting reaction, initiated by a chiral cinchona alkaloid-derived ammonium fluoride "precatalyst" complex, affords a variety of alkyl- and aryl-substituted 3,4-dihydrocoumarin products in excellent yield and with good enantioselectivity.
Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
Ethan
E
Alden-Danforth
Michael T
MT
Scerba
Thomas
T
Lectka
D000470:Alkaloids / Q000737:chemistry; D064751:Ammonium Compounds; D002384:Catalysis; D003500:Cyclization; D005459:Fluorides / Q000737:chemistry*; D045563:Indolequinones / Q000138:chemical synthesis* / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D013237:Stereoisomerism
D000470:Alkaloids; D064751:Ammonium Compounds; D045563:Indolequinones; D000644:Quaternary Ammonium Compounds; C068040:quinone methide; C024822:ammonium fluoride; D005459:Fluorides