Application of Silicon-Based Cross-Coupling Technology to Aryl Triflates
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The goal of this research was to explore the use of aryl silatranes as a replacement for aryl siloxanes in the palladium-catalyzed cross-coupling reaction with aryl triflates. Phenylsilatrane underwent fluoride-induced cross-coupling with aryl triflates to provide unsymmetrical biaryl derivatives in good to excellent yields. Typically, better yields of adduct were obtained for aryl triflates bearing electron-donating substituents than electron withdrawing substituents. Optimization of cross-coupling reaction revealed that addition of small amounts of water, the Denmark modification, dramatically improved reaction yields. Phenylsilatrane was found also to cross-couple in good to excellent yields with aryl halides having either electron-donating or electron-withdrawing substituents, although the yields of biaryl are lower than with the corresponding siloxane derivatives. Aryl siloxanes that had previously failed to couple with aryl triflates can be employed for triflate couplings using the Denmark modification although the yields of biaryls are generally lower than the corresponding silatrane reactions.