Visible-Light-Driven Enantioselective Free Radical Addition to Aldimines via Direct C-H Functionalization

Area of Science:

• Organic Chemistry
• Catalysis
• Photochemistry

Background:

• Enantioselective radical addition to imines is crucial for synthesizing optically active amines.
• Current methods often require radical precursors with directing groups for stereocontrol.

Purpose of the Study:

• To develop a novel catalytic asymmetric reaction for enantioselective radical addition to imines.
• To enable direct C-H functionalization of simple aromatic solvents without directing groups.

Main Methods:

• Chiral phosphoric acid-catalyzed, visible-light-driven photoredox catalysis.
• Direct benzylic C-H functionalization of aromatic solvents as radical precursors.
• Radical addition to imines.

Main Results:

• Successful enantioselective radical addition to imines using simple aromatic solvents.
• Broad substrate scope yielding various chiral amines.
• High enantioselectivities achieved, up to 93% ee.
• Mechanistic studies confirmed a pathway involving iminium radical cation intermediates.

Conclusions:

• This work presents a versatile strategy for asymmetric photoredox catalysis.
• It expands the utility of direct C-H functionalization in enantioselective synthesis.
• Provides a general platform for radical additions to imines without directing groups.