N,N-Di(4-halophenyl)nitrenium ions: nucleophilic trapping, aromatic substitution, and hydrogen atom transfer

Area of Science:

• Organic Chemistry
• Photochemistry
• Computational Chemistry

Background:

• Diarylnitrenium ions are key reactive intermediates in organic synthesis.
• Understanding their reactivity is crucial for developing new synthetic methodologies.
• Halogen substitution can significantly alter the properties of organic molecules.

Purpose of the Study:

• To generate and characterize halogenated diarylnitrenium ions.
• To investigate the influence of halogen substituents on nitrenium ion reactivity.
• To compare the behavior of halogenated nitrenium ions with unsubstituted diphenylnitrenium ion.

Main Methods:

• Generation of N,N-di(4-chlorophenyl)nitrenium and N,N-di(4-bromophenyl)nitrenium ions via photolysis.
• Characterization using laser flash photolysis and stable photoproduct analysis.
• Computational analysis using ab initio calculations and density functional theory.

Main Results:

• Halogenated diarylnitrenium ions exhibit longer lifetimes compared to diphenylnitrenium ion.
• Cyclization to carbazole derivatives is negligible for halogenated species.
• These ions participate in reactions with nucleophiles, arenes, electron acceptors, and abstract H atoms.

Conclusions:

• Halogenation stabilizes diarylnitrenium ions, altering their reaction pathways.
• Singlet ground states are predicted, with significant singlet-triplet energy gaps.
• The observed reactivity highlights the versatility of these halogenated intermediates in organic reactions.