title: Fe(OTf)3-catalyzed α-benzylation of aryl methyl ketones with electrophilic secondary and aryl alcohols.
abstract: Acid-catalyzed Friedel-Crafts alkylation of 1,3-dicarbonyl compounds with electrophilic alcohols, is known to be an effective C-C bond forming reaction. However, until now, this reaction has not been amenable for α-alkylation of aryl methyl ketones because of the notoriously low nucleophilicities of these compounds. Therefore, α-alkylation of aryl methyl ketone relies on precious metal catalysts and also, the use of primary alcohols is mandatory. In this study, we found that a system composed of a Fe(OTf)3 catalyst and chlorobenzene solvent is sufficient to promote the title Friedel-Crafts reaction by using benzhydrols as electrophiles. 3,4-Dihydro-9-(2-hydroxy-4,4-dimethyl-6-oxo-1-cyclohexen-1-yl)-3,3-dimethyl-xanthen-1(2H)-one was also applicable as an electrophile in this type of benzylation reaction. On the basis of this result, a three-component reaction of salicylaldehyde, dimedone, and aryl methyl ketone was also developed, and this provided an efficient way for the synthesis of densely substituted 4H-chromene derivatives.
authors.affiliation: Hubei Key Laboratory of Material Chemistry and Service Failure, Key Laboratory for Large-Format Battery Materials and System, Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology (HUST), 1037 Luoyu road, Hongshan District, Wuhan 430074 (China), Fax: (+86) 027-87-54-37-45.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Pan
authors.forename: Minghao
authors.initials: M
authors.lastname: Li
authors.forename: Yanlong
authors.initials: Y
authors.lastname: Gu
keywords: Friedel-Crafts reaction; alkylation; aryl methyl ketone; iron catalysis; three-component reaction