The Slow-Release Strategy in Suzuki-Miyaura Coupling

Despite great advances in metal-catalyzed cross-coupling reactions, their efficacy is often compromised by side reactions, reducing the yield, or requiring a large excess of one component. Suzuki-Miyaura cross-coupling is no exception, as the boronic acid functionality can be susceptible to a range of undesired processes. A number of methods have been developed to mitigate these side reactions, and herein we focus on the "slow-release" strategy. These conditions involve deployment of a "masking" reagent that protects the vulnerable boronic acid functionality from degradation, particularly protodeboronation, whilst simultaneously facilitating controlled liberation of the active reagent into the catalytic milieu. Under suitably tailored conditions, this dual-action approach ensures that the concentration of the free boronic acid is minimized, thus attenuating its degradation but still facilitating transmetallation of the organoboron species with the key organopalladium intermediate.