ABSTRACT: Although aryl(trialkyl)silanes are apparently ideal organometalic reagents for the cross-coupling reaction due to robustness, low toxicity, solubility, and easy accessibility, they are generally an inert cross-coupling nucleophile. Disclosed herein is that a palladium/copper catalytic system achieves the desired cross coupling of aryl-SiMe3, -SiEt3, -SiMe2(t-Bu), and -Si(i-Pr)3 with aryl bromides, allowing application to the sequential C–H and C–Si bond arylation of thiophenes and the synthesis of poly(thiophenefluorene)s.
Reaction of 1a with 2a
Scope of Substrates
Application in Sequential Arylation via C–H/C–Si Activation:
Among various organometallic nucleophiles in cross-coupling reactions, such as aryl boronic acids or stannes etc, organo(trialkyl)silanes have ideal characteristics in stability, high solubility in various organic solvents, non-toxicity, easy handling and high accessibility. But it usually has lower reactivity. In 2016, Y. Minami and T. Hiyama developed a direct cross-coupling of aryltrialkylsilanes with iodoarenes by using a copper(II) catalyst. Recently they reported Pd/Cu dual catalysis undergoes the cross-coupling of aryl(trialkyl)silanes with bromo/chloroarenes under mild conditions. A wide variety of silyl groups such as TMS, TES, TBS and TIPS as well as various aryl groups in both coupling partners are found to be applicable to the dual catalytic system. Although further elucidation of the reaction mechanism is necessary, this study has no doubt effectively expanded the cross-coupling reaction involving organosilicon.