Selective cross-coupling of molecules containing multiple reactive functional groups are highly valuable transformations in synthetic organic chemistry. The origin of selectivity in such reactions is frequently substrate-controlled, where high selectivity is achieved through directing groups or inherent differences in functional group reactivity. These approaches have disadvantages, however, including poor selectivity or atom economy, cost, catalyst poisoning by irreversible coordination of directing groups to metal catalysts, and difficulty removing directing groups later in a synthesis. We have recently developed a method for catalyst-controlled chemoselective Suzuki cross couplings using palladium catalysts bearing N-heterocyclic carbene (NHC) ligands. In this presentation, we examine the origin of selectivity control by NHC ligands and present experimental and computational mechanistic evidence that the operative selectivity control mechanism differs from other related systems.

Mechanistic origins of site-selectivity in Pd-NHC-catalyzed cross-couplings

2019 Fall National Meeting

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