title: Iron-catalyzed Friedel-Crafts benzylation with benzyl TMS ethers at room temperature.
abstract: Friedel-Crafts benzylations between unactivated arenes and benzyl alcohol derivatives are clean and straightforward processes to construct biologically useful di- and tri-arylmethanes. We have established an efficient iron-catalyzed Friedel-Crafts benzylation method at room temperature that uses benzyl TMS ethers as substrates, which are poorly reactive under common nucleophilic substitution conditions. The reaction seems to progress through iron-catalyzed self-condensation of the benzyl TMS ether to the corresponding dibenzylic ether. The use of excess arene relative to benzyl TMS ether produced mono-benzylated arene (di- and tri-arylmethane products), whereas the use of excess benzyl TMS ether versus arene provided bis-benzylated arene (polyarylated products) in high yields and regioselectivities. In previous methods, the latter double Friedel-Crafts benzylations hardly proceed.
authors.affiliation: Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4 Daigakunishi, Gifu 501-1196 (Japan), Fax: (+81) 58-230-8109. sawama@gifu-pu.ac.jp.
authors.forename: Yoshinari
authors.initials: Y
authors.lastname: Sawama
authors.forename: Yuko
authors.initials: Y
authors.lastname: Shishido
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kawajiri
authors.forename: Ryota
authors.initials: R
authors.lastname: Goto
authors.forename: Yasunari
authors.initials: Y
authors.lastname: Monguchi
authors.forename: Hironao
authors.initials: H
authors.lastname: Sajiki
keywords: Friedel-Crafts reaction; benzylation; biarylmethanes; iron; silyl ethers