Photoinduced copper-catalysed asymmetric amidation via ligand cooperativity

Abstract

The substitution of an alkyl electrophile by a nucleophile is a foundational reaction in organic chemistry that enables the efficient and convergent synthesis of organic molecules. Whereas substantial progress has been reported in recent years in exploiting transition-metal catalysis to dramatically expand the scope of nucleophilic substitution reactions using carbon nucleophiles, there has been limited progress in corresponding reactions with nitrogen nucleophiles. Furthermore, for many substitution reactions, the bond construction itself is not the only challenge, as there is a need to control stereochemistry at the same time. Here we describe a method for the enantioconvergent substitution of unactivated racemic alkyl electrophiles by a ubiquitous nitrogen-containing functional group, an amide, through the use of a photoinduced catalyst system based on copper, an earth-abundant metal. This process for asymmetric N-alkylation relies upon three distinct ligands: a bisphosphine, a phenoxide and a chiral diamine, that assemble, in situ, a copper/bisphosphine/phenoxide complex that serves as a photocatalyst and a chiral copper/diamine complex that catalyzes enantioselective C–N bond formation. This study thus expands enantioselective N-substitution by alkyl electrophiles beyond activated electrophiles (those bearing at least one sp- or sp²-hybridized substituent on the carbon undergoing substitution) to include unactivated electrophiles.

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