Advanced 1,1-carboboration reactions with pentafluorophenylboranes

Area of Science:

• Organoboron Chemistry
• Synthetic Organic Chemistry
• Heterocyclic Chemistry

Background:

• The Wrackmeyer reaction traditionally uses trialkylboranes for 1,1-carboboration of metal-substituted alkynes.
• Conventional methods often require harsh conditions and have limitations with certain alkyne substrates.

Purpose of the Study:

• To explore the utility of electrophilic R-B(C6F5)2 reagents in 1,1-carboboration reactions.
• To develop milder and more versatile synthetic routes to alkenylboranes and heterocyclic compounds.

Main Methods:

• 1,1-carboboration of terminal and internal alkynes with R-B(C6F5)2 reagents.
• Sequential 1,1-carboboration of geminal bis(alkynyl) compounds.
• Investigation of benzannulation reactions with vicinal bis(alkynyl)arenes/heteroarenes.

Main Results:

• Efficient synthesis of bulky alkenylboranes from terminal alkynes via 1,2-hydride migration.
• Carboboration of internal alkynes yielding alkenylboranes through C-C bond cleavage.
• Formation of boryl-substituted phospholes, thiophenes, and boroles via sequential carboboration.
• Benzannulation of arenes and heteroarenes.
• Demonstration of the utility of products in cross-coupling reactions.

Conclusions:

• R-B(C6F5)2 reagents offer a milder and more versatile approach to 1,1-carboboration.
• This methodology provides access to diverse organoboron compounds and heterocyclic systems.
• The synthesized compounds serve as valuable intermediates in further synthetic transformations.