Triflate‐Selective Suzuki Cross‐Coupling of Chloro‐ and Bromoaryl Triflates Under Ligand‐Free Conditions

Abstract

In the absence of strong ancillary ligands such as phosphines or N-heterocyclic carbenes, palladium salts are selective for CÀ OTf cleavage in the room-temperature Suzuki couplings of chloroaryl triflates in acetonitrile. Similar "ligandfree" conditions in DMSO also promote triflate-selective Suzuki coupling of bromoaryl triflates. This triflate selectivity complements the typical preference for reaction of bromides in prior reports of Suzuki couplings using phosphine ligands. DFT calculations and additional experimental evidence are consistent with triflate-selective oxidative addition taking place at homogeneous, possibly mononuclear, anionic palladium supported by a solvent molecule.

Recent advances in the application of ligands in palladium-catalyzed chemoselective coupling reactions at C–Br, C–OTf, and C–Cl sites

“…In addition to catalysts, solvents, 12,13 and additives, 14 the intrinsic electronic properties of polyhalogenated heteroarenes with the same or different ( pseudo)halogens attached to the same ring can also affect chemoselectivity. 11,15 While there have been intriguing findings in this area, this article solely focuses on chemoselective palladium-catalyzed coupling reactions involving aryl bromides, aryl triflates, and aryl chlorides, which are the most commonly used aryl ( pseudo)halides.…”

Recent Advances in Pd‐Catalyzed Suzuki‐Miyaura Cross‐Coupling Reactions with Triflates or Nonaflates

“…Furthermore, conversion of 2‐ and 4‐pyridinetriflates does not work under the reaction conditions, due to competing triflate hydrolysis. Sterically hindered triflates were not converted [34] …”

Organopalladium Catalysis as a Proving Ground for Data-Rich Approaches to Reaction Development and Quantitative Predictions

“…Given we used Pd­(PCy 3 ) 2 as the Pd(0) source to generate our model, this consistency with simple phosphines makes sense. Neufeldt’s group have assessed factors that lead to unconventional site selectivity in Pd-catalyzed coupling, many of which are related to ligand and/or solvent identity, and their impacts on Pd speciation. ,,− Future work in QSRR modeling for oxidative addition must therefore endeavor to capture these ligand/solvent/speciation effects.…”