Catalytic
functionalization of alkynes with organoboron reagents
provides a straightforward access to stereochemically defined multisubstituted
alkenes, which are structural motifs commonly found in bioactive compounds
and organic materials. Recent progress has substantially broadened
the scope of this field on several fronts. Strategies for regioselectivity
control in the 1,2-migratory insertion across unsymmetrical internal
alkynes, as well as for the direct access to products with anti-insertion stereochemistry, have been devised. The alkenyl-to-aryl
1,4-metal migration upon metal insertion has been recently exploited
in powerful cascade sequences leading to complex polycyclic scaffolds,
including the development of enantioselective processes. Elegant enantiospecific
and dynamic kinetic resolution methods have been developed for accessing
chiral allenes from propargylic alcohol derivatives. Mechanistic manifolds
have emerged based on single-electron transfer (SET) that have provided
a fresh impetus for alkyne 1,2-difunctionalization with complementary
stereoselectivity to processes relying on 1,2-insertion of R–M
species. Herein, we discuss the most recent advances in transition-metal-catalyzed
functionalization of alkynes using organoboron reagents, categorized
according to the type of mechanistic outcome. Emphasis is placed on
mechanistic aspects, synthetic utility, limitations, and challenges
for future research.