Mechanochemically Activated Liebeskind-Srogl (L-S) Cross-Coupling Reaction: Green Synthesis of meso-Substituted BODIPYs

In the past decade mechanochemistry has become a highly versatile solvent-free methodology that fulfills several principles of so-called green chemistry. In this regard, we describe a mechanochemical activation protocol for the synthesis of several relevant meso-aryl-substituted BODIPYs via the Liebeskind-Srogl cross-coupling reaction with excellent yield and very short reaction times relative to alternative procedures in solution, thereby avoiding the use of bulk solvent. In contrast with previous assertions that the L S reaction requires anaerobic conditions to avoid the oxidation of Cu(I) to Cu(II), our results seem to indicate that this paradigm may not be altogether accurate, since the L-S reactions studied here took place under aerobic conditions, possibly suggesting an alternative reaction mechanism.