Divergent Syntheses of 2‑Aminonicotinonitriles and Pyrazolines by Copper-Catalyzed Cyclization of

ABSTRACT: Copper-catalyzed cyclization of an oxime ester toward divergent heterocycle synthesis is reported. Oxime ester serves as an enamine precursor to cyclize with malononitrile and aldehydes for access to 2-aminonicotinoni-triles in a one-pot reaction, while cyclizing with N-sulfonylimines leads to synthesis of pyrazolines. Divergent synthesis allows the rapid entry to structurallydiverse compounds from the same starting material and therefore has been a popular and useful tool in the discovery of bioactive molecules and functional materials.1 The success of divergent synthesis requires precise control of the chemo- and regioselectivity and a careful selection of the reaction conditions, guided by an understanding of the reactivity of intermediates and substrates.2 So far, transition-metal-catalyzed cyclization has emerged as a powerful and distinct approach in the divergent synthesis of nitrogen-containing heterocycles.