Strategies for the Catalytic Synthesis of Nitrogen-Containing Molecules

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Project Abstract for NIH R35 (MIRA): The discovery and development of new methods for the efficient synthesis of N-containing and F-containing chemical building blocks is an important goal in organic synthesis as a large number of pharmaceuticals and other bioactive molecules contain these atoms within a diverse set of chemical functional groups. More rapid and/or selective assembly of known motifs, and moreover the preparation of new chemical landscapes, requires innovative approaches to drug-like scaffolds, including the discovery of new reagents and new catalysts/catalytic strategies. The current goals of this project fall under three main focus areas. 1) We will develop 2-azatrienes, a novel class of enamine umpolung reagents, for myriad catalytic enantioselective approaches towards chiral amines. Representative reactions that will be developed include 6,3-, 6,5- and 5,6-hydrofunctionalizations including reductive couplings with carbonyls and imines, hydroalkynylations, and hydroarylations. Azadienes generated from 6,5- and 5,6-hydrofunctionalizations of the azatriene reagents may be utilized in myriad downstream reactions, including other catalytic processes, thereby providing a diastereodivergent avenue towards highly complex chiral amines through sequential catalysis. 2) We will expand upon our prior work in enantioselective transformations of 2-azadienes, the first class of enamine umpolung reagents developed in our laboratory. Examples include reductive couplings with aromatic heterocycles, such as quinoline N-oxides, catalytic enantioselective fluorofunctionalizations with 4,4-difluoro-2-azadienes, cascade desymmetrization reactions, and reductive [3+2]-cycloadditions. 3) We will develop catalytic remote C–C and C–B coupling reactions that result in the loss of a halide from a trifluoromethyl group or H-atom abstraction from a difluoromethyl group to deliver difluorocarbons in a number of settings. In one case, we will carry out borylation or enantioselective alkylation of a 3-trifluoromethylpyridine scaffold to yield medicinally important and highly functionalized 3- (difluoromethyl)pyridines. In another area, we will execute a radical hydrogen atom abstraction of 4- difluoromethyl-2-azadienes to furnish a difluoro-2-azapentadienyl radical, which then may be engaged in catalytic cross-couplings to furnish chiral allylic amines bearing a difluoroalkene unit. Together, these undertakings will enable new chemical space for drug discovery to be obtained readily and with great diversity from simple reagents. We will access more established N-containing motifs more quickly and with greater levels of regio/stereocontrol compared to known approaches because of the invention of new reagents and the novel reactivity that they embody.