title: A novel alpha-arylation of ketones, aldehydes, and esters via a photoinduced SN1 reaction through 4-aminophenyl cations.
abstract: 4-Aminophenyl cations (expediently generated by photolysis of 4-chloroaniline and its N,N-dimethyl derivative by photolysis in MeCN) added to enamines and gave the corresponding alpha-(4-aminophenyl) ketones in satisfactory yields. The yields of the same ketones were increased when silyl enol ethers were used in the place of enamines. The alpha-arylation of silyl enol ethers of aldehydes occurred with lower yields and only with the N,N-dimethyl derivative. The procedure was successful with ketene silyl acetals giving in a single step a good yield of alpha-(4-aminophenyl)propionic(acetic) esters, known intermediates for the preparation of analgesic compounds. The reaction of the aryl cation with Danishefsky's diene gave the arylated beta-methoxy enone. The method is complementary to the recently developed palladium-catalyzed alpha-arylation and occurs under neutral conditions.
authors.affiliation: Department of Organic Chemistry, University of Pavia, Viale Taramelli 10, 27100 Pavia, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Fraboni
authors.forename: Maurizio
authors.initials: M
authors.lastname: Fagnoni
authors.forename: Angelo
authors.initials: A
authors.lastname: Albini