Nickel-mediated aerobic C(sp2)–nucleophile coupling reactions for late-stage diversification of aryl electrophiles
摘要
The structural diversification of pharmaceutically relevant compounds presents unique challenges to catalytic methodologies that have been developed and optimized on simpler substrates that lack drug-like complexity. Here we report a general strategy for carbon–heteroatom (C–X) bond formation through reactions between a wide range of nucleophiles and nickel-based oxidative addition complexes of drug-like aryl and heteroaryl electrophiles. These organonickel complexes are easily synthesized by oxidative addition of the corresponding electrophiles under electroreductive conditions using an inexpensive nickel precursor. Redox-induced oxidative coupling from these persistent complexes proved challenging, but mechanistic studies guided the development of a simple aerobic oxidation procedure to rapidly form C–X coupled products. Exposure of the organonickel complexes to ambient air forms a high-valent (peroxo)NiIIIAr complex intermediate that can undergo substitution with a variety of nitrogen-, oxygen-, sulfur-, carbon-, phosphorus- or halide-based nucleophiles, which are incorporated into the product. The breadth of this methodology was demonstrated by reactions with unreactive electrophiles, such as aryl chlorides, drug-like (hetero)aryl electrophiles and small peptides. Finally, the aerobic chemistry was miniaturized to allow for high-throughput exploration of substrate diversity with an equally complex set of nucleophilic partners.