Synthesis of nitrogenous heterocycles via group 3 metal-catalyzed hydroamination and zinc (II) mediated metalloamination
Smith, Adrian Robert.
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Pyrrolidines and piperidines respresent a motif found in a wide array of bioactive compounds. Hydroamination, or the insertion of a carbon-nitrogen bond into a site of unsaturation, represents an atom economical method for accessing substituted pyrrolidines and piperidines. Synthesis of nitrogenous heterocycles through group 3 metal hydroamination and zinc(II) metalloamination has been achieved. The hydroamination of aminoalkenes has been thoroughly screened and has shown good tolerance for ethereal solvents, and solvent choice can result in improved rate and diastereoselectivity. The hydroamination of secondary amines with electron rich heteroatoms has also been realized utilizing a new group 3 metal trisamide developed in these labs. Additionally, zinc(II) metalloamination has been performed on N,N-dimethylhydrazinoalkenes and successfully resulted in the synchronous formation of a nitrogen-carbon bond to form a ring as well as carbon-zinc bond formation at the adjacent carbon. This carbon-zinc bond has been intercepted by different carbon electrophiles to synchronously form a nitrogen-carbon bond and carbon-carbon bond in situ. Ligand studies for these transformations suggest 1,1,1-trifluoroacetylenamines as well as acetoacetamides are promising motifs for future ligand scaffolds due to their ease of synthesis, low cost, and good reactivity with a range of N,N-dimethylhydrazinoalkene substrates.