A meta-selective C-H borylation directed by a secondary interaction between ligand and substrate

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• Regioselective C-H bond transformations offer efficient organic synthesis routes.
• Controlling regioselectivity in C-H functionalization is challenging due to multiple reactive sites.
• Existing methods often rely on directing groups for ortho-selectivity.

Purpose of the Study:

• To develop a novel catalytic system for meta-selective C-H borylation of aromatic compounds.
• To investigate the mechanism of regioselectivity control using a designed ligand.
• To demonstrate a versatile strategy for directing C-H functionalization via hydrogen bonding.

Main Methods:

• Design and synthesis of an iridium catalyst featuring a bipyridine ligand with a pendant urea moiety.
• Application of the catalytic system to aromatic substrates for C-H borylation.
• Utilizing (1)H NMR spectroscopy and control experiments to elucidate the reaction mechanism.

Main Results:

• Achieved meta-selective C-H borylation of aromatic compounds using the new iridium catalyst.
• Demonstrated that the pendant urea moiety on the ligand directs regioselectivity through hydrogen bonding interactions with the substrate.
• Confirmed the crucial role of hydrogen bonding in controlling the catalyst's position and reactivity.

Conclusions:

• The developed catalytic system enables efficient meta-selective C-H borylation.
• Hydrogen bonding interactions provide a versatile strategy for directing regioselective C-H transformations.
• This approach offers a new paradigm for controlling selectivity in organic synthesis.