Oxidative Three-Component Carboamination of Vinylarenes with Alkylboronic Acids

The
three-component carboamination of alkenes is of significant
interest due to the ease by which functionalized amines can be produced
from readily available chemical building blocks. Previously, a variety
of carbon-centered radical precursors have been studied as the carbon
components for this reaction; however, the use of general alkyl sources
has remained as an unsolved challenge. Herein we present our efforts
to develop an oxidative carboamination protocol that utilizes alkylboronic
acids as carbon-centered radical precursors. The presented work demonstrates
34 examples, ranging from 17 to 88% yields, with a broad scope in
vinylarenes, amines, and alkylboronic acids. Preliminary mechanistic
studies suggest that a single-electron oxidation of the alkylboronic
acid generates a carbon-centered radical intermediate that adds across
the olefin followed by C–N bond formation via Cu-mediated inner-sphere
or carbocation-mediated pathways.