Iron‐Catalyzed Friedel–Crafts Benzylation with Benzyl TMS Ethers at Room Temperature |
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Authors: | Dr. Yoshinari Sawama Yuko Shishido Takahiro Kawajiri Ryota Goto Dr. Yasunari Monguchi Prof. Dr. Hironao Sajiki |
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Affiliation: | Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1‐25‐4 Daigakunishi, Gifu 501‐1196 (Japan), Fax: (+81)?58‐230‐8109 |
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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. |
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Keywords: | benzylation biarylmethanes Friedel– Crafts reaction iron silyl ethers |
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