Halogen-atom and group transfer reactivity enabled by hydrogen tunneling

Area of Science:

• Organic Chemistry
• Physical Chemistry
• Reaction Mechanisms

Background:

• Traditional carbon radical generation relies on tin and silicon reagents, balancing thermodynamic and kinetic factors.
• These methods often require specific conditions to maximize enthalpic and polar effects for efficient halogen-atom and group transfer.

Purpose of the Study:

• To introduce a new reactivity mode for carbon radical generation.
• To explore the use of quantum mechanical tunneling in chemical reactions.
• To activate alkyl/aryl halides, alcohols, and thiols using a novel abstractor.

Main Methods:

• Utilizing γ-terpinene as a cyclohexadiene derivative abstractor.
• Employing mild photochemical conditions for radical generation.
• Conducting experimental and computational studies to elucidate the reaction pathway.

Main Results:

• Demonstrated a distinct reactivity mode enabled by quantum mechanical tunneling.
• Successfully activated a range of alkyl/aryl halides, alcohols, and thiols.
• Unveiled a noncanonical reaction pathway involving a cyclohexadienyl radical.

Conclusions:

• Quantum tunneling provides a feasible pathway for thermodynamically and kinetically unfavorable reactions.
• This protocol offers a novel and mild approach to carbon radical generation.
• The mechanism involves concerted aromatization and abstraction via an effective H atom.