Zirconium-Catalyzed Synthesis of Alkenylaminoboranes:
From a Reliable Preparation of Alkenylboronates to a Direct Stereodivergent
Access to Alkenyl Bromides
A simple procedure
has been optimized for the preparation of alkenylaminoborane
from alkynes using diisopropylaminoborane and HZrCp2Cl.
Coupled with a magnesium-catalyzed dehydrogenation, it allowed for
the use of air- and moisture-stable diisopropylamine. This synthesis
has been extended to a one-pot sequence leading directly to bromoalkenes
with controlled stereochemistry. As such, it provides an easy, scalable,
cheap process to access alkenylboronates and both (E)- and (Z)-bromoalkenes from commercially available
alkynes.