Potassium <i>tert</i>-Butoxide Promoted Intramolecular Arylation via a Radical Pathway
作者:Daniela Sustac Roman、Yoko Takahashi、André B. Charette
DOI:10.1021/ol201160s
日期:2011.6.17
Potassium tert-butoxide mediated intramolecular cyclization of aryl ethers, amines, and amides was efficiently performed under microwave irradiation to provide the corresponding products in high regioisomeric ratios. The reaction proceeds via single-electron transfer to initiate the formation of an arylradical, followed by a kinetically favored 5-exo-trig and subsequent ring expansion.
The reaction of o-(trimethylsilylethynyl)styrenes with diisobutylaluminum hydride (DIBAL-H) provides 2-trimethylsilyl-1H-indenes efficiently. The cyclization mechanism involves regioselective hydroalumination of the alkynyl moiety, geometrical isomerization of the alkenylaluminums formed, and intramolecular carboalumination. With substrates bearing a 2-(trimethylsilyl)ethenyl group (R-1 = Me3Si, R-2 = R-3 = H), bis-silylated benzofulvenes are obtained upon treatment of the reaction mixture with an excess amount of benzaldehyde.