Pd and Fe Cocatalyzed Synthesis of Remotely Borylated Aza-Heterocycles

We report the intramolecular 1,n-aminoboration
for the simultaneous synthesis of aza-heterocycles with distal carbon–boron
bonds. Pd-catalyzed remote 1,n-aminoboration occurs
with 1,2-disubstituted alkenes; upon aminopalladation of the olefin,
chain walking generates the terminal Pd-alkyl intermediate, which
selectively undergoes Fe-catalyzed borylation. Terminal bishomoallylic
amines, amides, carbamates, and ureas afford the borylated pyrrolidines
and lactams through 1,2-aminoboration. Forty-one examples of 1,n-borylated heterocycles are presented with yields up to
92%. Derivatization of the products is explored: cross-coupling, amination,
and oxidation to access unnatural amino alcohols and acids.