Selective Monoarylation of Ammonium Triflate with Aryl Chlorides Catalyzed by [Pd(β‐MeNAP)Br]₂ and AdBrettPhos

Abstract

The selective introduction of a primary amino group into aromatic compounds is a desirable transformation, but is challenging due to competing double arylation. A catalyst generated from β‐methylnaphthyl (MeNAP) palladium bromide and the bulky ligand biphenyl‐diadamantylphosphine (AdBrettPhos) has been found to promote the amination even of non‐activated aryl chlorides with ammonium triflate within 30 min at 80 °C to the primary anilines. The efficiency of the protocol was evaluated in comparative experiments, its versatility documented by the synthesis of various primary anilines including drug‐like molecules.

Pd-Methylnaphthyl-tBuBrettPhos Complexes as Efficient and Selective Catalysts for the Monoarylation of Ammonia and Hydrazine

“…The 31 P NMR spectrum shows a new signal at 61.1 ppm, which is in the expected range of Pd(0) species bearing a t BuBrettPhos ligand. This is in agreement with an activation pathway, in which the MeNAP substituent is liberated by reductive elimination of aminomethyl naphthalene . The resulting Pd(0) species is rather labile and rapidly decomposes with formation of palladium black and free ligand in the absence of aryl halide substrates.…”

“…The high activity of preformed [Pd(1-MeNAP)( t BuBrettPhos)Br] in the coupling of ammonium triflate is illustrated by the examples in Table . In all cases, the one-component catalyst gave strongly improved yields in comparison to that reported for a catalyst generated in situ from expensive AdBrettPhos . Even 1-chloronaphthalene ( 7 ), which marked the performance limit of the benchmark system, was smoothly converted.…”

“…We have recently introduced methylnaphthyl (MeNAP) Pd complexes as easy-to-use catalyst precursors with a high activity in various cross-coupling reactions . In combination with bulky, electron-rich AdBrettPhos, [Pd­(2-MeNAP)­Br] 2 efficiently promotes the monoarylation of ammonium triflate with aryl chlorides with exceptional selectivity within short reaction times . MeNAP precatalysts rapidly and cleanly activate to give monoligated Pd(0) species, which results in improved yields and selectivities.…”