Pd-Catalyzed Suzuki-Miyaura Cross-Coupling of Pentafluorophenyl Esters.

Although the palladium-catalyzed Suzuki-Miyaura cross-coupling of aryl esters has received significant attention, there is a lack of methods that utilize cheap and readily accessible Pd-phosphane catalysts, and can be routinely carried out with high cross-coupling selectivity. Herein, we report the first general method for the cross-coupling of pentafluorophenyl esters (pentafluorophenyl = pfp) by selective C⁻O acyl cleavage. The reaction proceeds efficiently using Pd(0)/phosphane catalyst systems. The unique characteristics of pentafluorophenyl esters are reflected in the fully selective cross-coupling vs. phenolic esters. Of broad synthetic interest, this report establishes pentafluorophenyl esters as new, highly reactive, bench-stable, economical, ester-based, electrophilic acylative reagents via acyl-metal intermediates. Mechanistic studies strongly support a unified reactivity scale of acyl electrophiles by C(O)⁻X (X = N, O) activation. The reactivity of pfp esters can be correlated with barriers to isomerization around the C(acyl)⁻O bond.