Suzuki–Miyaura monocouplings of p-dibromobiphenyl and substituted p-dibromo(penta-p-phenylenes)

Selective Mechanochemical Monoarylation of Unbiased Dibromoarenes by in Situ Crystallization

“…17 However, many of these approaches are costly and wasteful. Although the monoarylation of unbiased dihaloarenes with certain halide groups through elaborate catalyst design and/or the fine-tuning of reaction parameters such as temperature, solvent, and additives has been reported, [18][19][20][21][22] the exploration of conceptually new and generally applicable strategies to control and improve the monoarylation selectivity remains in high demand. We have previously reported broadly applicable solidstate cross-coupling reactions using mechanochemistry.…”

Controlling substrate selectivity in cross coupling with light

“…This result was surprising given the precedent for diiodoarenes to favor bis-substitution under thermal cross-coupling conditions. 21,25 Other monoarylation methods based on ground-state selectivity typically use 1-1.5 equiv of the coupling partner to discourage further reaction. Consistent with the absence of ground-state selectivity, traditional thermal Pd-catalyzed conditions (entry 2) favor bis-substituted product 3b.…”

“…Next, we explored the scope of this cross-coupling with respect to the BODIPY substrate (Table 3). Diiodo-BODIPYs containing methyl, phenyl, or para-substituted aryl groups at the meso position all provided the mono-substituted products in 34-72% yield, using Condition A for electron-rich boronic acids (22,24,26) and Condition B for electron-neutral and -poor boronic esters (23,25). Notably, placing a sterically hindered mesityl substituent at the meso position (BODIPY 28) altered the selectivity of the photoinduced cross-coupling.…”

“…[15][16][17][18][19] For substrates with multiple identical C-X bonds, however, distinguishing between the starting material and the product requires substrate selectivity rather than regio-or chemoselectivity (Figure 1c). 20 Typically, monoselectivity can only be achieved if the first substitution significantly deactivates the remaining C-X bonds through steric or electronic effects, [21][22][23][24][25][26][27][28] changes in solubility, 29 or selective crystallization of the product. 30 Substrate selectivity thus originates in differences between groundstate physical and chemical properties.…”

Nucleophilic Aromatic Substitution

“…However, their role is a compromise as they disfavour reaction by forming of unreactive anionic trihydroxyborate. 116 The use of N-heterocyclic carbene ligands for palladium has allowed the formation of bulky tetra-ortho-substituted biphenyls by reaction of boronic acids with aryl bromides and chlorides. It works at room temperature in toluene solvent in the presence of water and potassium carbonate.…”