title: Urea-induced acid amplification: a new approach for metal-free insertion chemistry.
abstract: The enhanced catalytic activity of difluoroboronate ureas proved to be essential as an acidity amplifier to promote metal-free O-H and S-H insertion reactions of α-aryldiazoacetates in high yield. This methodology was found to be generally applicable to a broad substrate scope and presents a conceptually new approach for organocatalytic diazo insertion reactions. Mechanistic investigations suggest that the reaction pathway involves a urea-induced protonation of the α-aryldiazoester.
authors.affiliation: Department of Chemistry and Biochemistry, The Ohio State University, 100 W. 18th Ave, Columbus, OH, 43210 (USA).
authors.forename: Erica D
authors.initials: ED
authors.lastname: Couch
authors.forename: Tyler J
authors.initials: TJ
authors.lastname: Auvil
authors.forename: Anita E
authors.initials: AE
authors.lastname: Mattson
keywords: acidity; diazo compounds; insertion; organocatalysis; urea