RESUMO
The Suzuki-Miyaura (SM) reaction is one of the most important methods for C-C bond formation in chemical synthesis. In this communication, we show for the first time that the low toxicity, inexpensive element zinc is able to catalyze SM reactions. The cross-coupling of benzyl bromides with aryl borates is catalyzed by ZnBr2 , in a process that is free from added ligand, and is compatible with a range of functionalized benzyl bromides and arylboronic acid pinacol esters. Initial mechanistic investigations indicate that the selective in situ formation of triaryl zincates is crucial to promote selective cross-coupling reactivity, which is facilitated by employing an arylborate of optimal nucleophilicity.
RESUMO
Tetramethylethylenediamine (TMEDA) acts as cheap and readily removed ligand in the iron-catalyzed coupling of alkyl Grignard reagents and activated aryl chlorides. The use of TMEDA allows for low ligand and iron catalyst loading as well as an increased reaction concentration and an ambient reaction temperature on a mole scale.