Aryl bromide/triflate selectivities reveal mechanistic divergence in palladium-catalysed couplings; the Suzuki–Miyaura anomaly

Abstract

In palladium-catalysed cross-coupling reactions, the outcome of competition between aryl bromides and aryl triflates depends on the nucleophilic partner; Suzuki couplings with R-B generally follow a different pattern from other R-M species.

Biaryl and Aryl Ketone Synthesis via Pd‐Catalyzed Decarboxylative Coupling of Carboxylate Salts with Aryl Triflates

“…[30] Their propensity to undergo oxidative addition is high, at a level comparable to that of aryl bromides. [31] As aryl triflates are generated from phenols, which in turn are usually accessed via different synthetic routes than aryl halides, they ideally complement the spectrum of substitution patterns available for the electrophilic coupling partner. Unfortunately, aryl triflates are prone to side reactions that are not observed for aryl halides, the most important being a cleavage of the triflate ester by water or nucleophiles under liberation of the corresponding phenol or phenyl ester.…”

Competitive and Selective Csp3Br versus Csp2Br Bond Activation in Palladium‐Catalysed Suzuki Cross‐Coupling: An Experimental and Theoretical Study of the Role of Phosphine Ligands

“…The species are labelled as Mnth, in which M is the phosphine: A for PA C H T U N G T R E N N U N G (Ph 3 ) and F for P(1-naphthyl) 3 ; n is the number of phosphines involved: 1 for PdA C H T U N G T R E N N U N G (PR 3 ), and 2 for PdA C H T U N G T R E N N U N G (PR 3 ) 2 ; t is the nature of the species: add stands for adduct before the transition state, and ts for the transition state; and h shows the hybridisation of the activated carbon: 3 for sp 3 carbon and 2 for sp 2 . Values are enthalpies in solution (DE sol ) relative to the reactants (PdA C H T U N G T R E N N U N G (PR 3 ) 1,2 plus 1 a) at infinite separation.…”

“…This PdA C H T U N G T R E N N U N G (PR 3 ) complex is more reactive, but its formation de- Table 3. PdA C H T U N G T R E N N U N G (OAc) 2 3 -catalysed Suzuki coupling. External competition experiments.…”

“…A different situation is observed for the bisphosphine species A2ts2 and A2ts3. The interaction term still favours sp 2 ). Thus, the key lies in the distortion terms for the bisphosphine systems.…”

Palladium‐Catalysed Cross‐Coupling and Related Processes: Some Interesting Observations That Have Been Exploited in Synthetic Chemistry

“…[191] However, in Suzuki couplings, bromide displacement occurs, the pathway of which was deemed normal after isolation of the expected oxidative addition Scheme 59. A preference for bromide in Suzuki couplings.…”