Challenging nickel-catalysed amine arylations enabled by tailored ancillary ligand design

Abstract

Palladium-catalysed C( sp ²)–N cross-coupling (that is, Buchwald–Hartwig amination) is employed widely in synthetic chemistry, including in the pharmaceutical industry, for the synthesis of (hetero)aniline derivatives. However, the cost and relative scarcity of palladium provides motivation for the development of alternative, more Earth-abundant catalysts for such transformations. Here we disclose an operationally simple and air-stable ligand/nickel(II) pre-catalyst that accommodates the broadest combination of C( sp ²)–N coupling partners reported to date for any single nickel catalyst, without the need for a precious-metal co-catalyst. Key to the unprecedented performance of this pre-catalyst is the application of the new, sterically demanding yet electron-poor bisphosphine PAd-DalPhos. Featured are the first reports of nickel-catalysed room temperature reactions involving challenging primary alkylamine and ammonia reaction partners employing an unprecedented scope of electrophiles, including transformations involving sought-after (hetero)aryl mesylates for which no capable catalyst system is known.

Abstract

The development of highly effective Earth-abundant catalysts for C( sp ²)-N cross-coupling represents an on-going challenge in synthetic chemistry. Here, the authors report a nickel complex containing a bisphosphine ancillary ligand allowing room-temperature couplings of amines and ammonia with a range of electrophiles.