Spiro-fluorene-indenoindenyl-Ir(I) complex-catalyzed, 1,3-azole-directed C(sp³)-H borylation with pinacolborane

Area of Science:

• Organometallic Chemistry
• Catalysis
• Synthetic Organic Chemistry

Background:

• Directed C(sp3)-H borylation of azoles is difficult due to catalyst deactivation.
• The reduction of the C-N bond by pinacolborane (HBpin) is a common side reaction.
• Existing methods often require harsh conditions or specialized reagents.

Purpose of the Study:

• To develop a novel catalytic system for efficient C(sp3)-H borylation of 1,3-azoles.
• To overcome the limitations of existing borylation methods, including catalyst deactivation and C-N bond reduction.
• To achieve this transformation under mild, near-room temperature conditions.

Main Methods:

• Utilized a unique spiro-fluorene-indenoindenyl-Iridium(I) complex as the catalyst.
• Employed pinacolborane (HBpin) as the boron source.
• Performed the borylation reaction at near-room temperature.

Main Results:

• Achieved successful C(sp3)-H borylation of 1,3-azoles with high efficiency.
• Demonstrated that the reaction proceeds at near-room temperature.
• Crucially, observed no undesired C-N bond reduction, a significant improvement over previous methods.

Conclusions:

• The developed spiro-fluorene-indenoindenyl-Ir(I) catalyst system is highly effective for directed C(sp3)-H borylation of azoles.
• This method offers a mild and efficient alternative for synthesizing organoboron compounds.
• The avoidance of C-N bond reduction broadens the scope and applicability of azole borylation.