Umpolung Reactivity of in Situ Generated Phosphido-Boranes: An Entry to P‑Stereogenic Aminophosphine-Boranes

The
synthesis of P-stereogenic aminophosphine-boranes has been
developed on the basis of umpolung reactivity of in situ generated
alkylarylphosphido-boranes, which are normally configurationally unstable
intermediates. In our case, their high configurational stability was
due to the slow release of the hydroxyalkyl protecting group, together
with the fast formation of the iodophosphanylborane in the presence
of N-iodosuccinimide. The subsequent substitution
reaction was found to proceed in moderate to good yields and in a
very high stereospecifity (es) using a variety of amines as nucleophiles.