Visible Light Induced B-H Bond Insertion Reaction with Diazo Compounds

Area of Science:

• Organic Chemistry
• Organometallic Chemistry
• Photochemistry

Background:

• Amine-borane adducts are versatile reagents in organic synthesis.
• Direct functionalization of the B-H bond remains a synthetic challenge.
• Metal-catalyzed and photocatalyzed methods often require specific conditions or reagents.

Purpose of the Study:

• To develop a metal-free and photocatalyst-free protocol for α-carbonyl carbene insertion into the B-H bond of amine-borane adducts.
• To establish a direct and efficient synthetic route to organoboron compounds.
• To investigate the mechanism of the photoinduced reaction.

Main Methods:

• Visible light irradiation of α-diazo esters and amine-borane adducts.
• Metal-free and photocatalyst-free reaction conditions.
• Mechanistic studies including investigation of rate-determining steps.

Main Results:

• Successful direct insertion of α-carbonyl carbenes into the B-H bond of amine-borane adducts was achieved.
• The protocol provides a straightforward route to various organoboron compounds.
• Moderate to good yields were obtained for the synthesized organoboron compounds.
• Mechanistic studies indicated a concerted carbene insertion mechanism.

Conclusions:

• A novel, metal-free, and photocatalyst-free protocol for synthesizing organoboron compounds has been established.
• Visible light photoredox catalysis offers an efficient method for direct B-H functionalization.
• The reaction proceeds via a concerted carbene insertion mechanism, with carbene generation as a potential rate-determining step.