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.
Sulfones are excellent candidates for the design of new C–C and C–X bond-forming reactions owing to the easy activation of C–S bonds. This review focuses on challenges and recent opportunities for catalytic functionalization of sulfones.
The stereoselective photoisomerization of olefins via Energy Transfer (EnT) sensitization bears significant potential in the context of rational design of catalytic stereodivergent methodologies. Whereas approaches for controlling the access to E‐ and Z‐ isomers depend highly on the nature of the catalyst – and therefore are not easily implemented as a general strategy – EnT catalysis has emerged in recent years as an increasingly powerful tool for olefin geometry control in a nearly perfect step‐economic fashion. Moreover, this approach presents both high functional group tolerance and, most notably, has demonstrated ample multicatalytic compatibility. This feature has enabled the development of tandem stereodivergent catalytic strategies, which are the focus of this Review.
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