Theoretical studies on iron-catalyzed azaindoline formation: mechanism and site-selectivity

The mechanism and site-selectivity for Fe-catalyzed azaindoline formation from 1,2,3,4-tetrazole were examined computationally. The H-atom abstraction/radical rebound stepwise mechanism is proposed. The aliphatic H-atom abstraction (HAA) vs. electrophilic aromatic substitution (EAS) steps are responsible for the sp(3)vs. sp(2) C-H amination site-selectivity and a larger steric congestion disfavors sp(2) EAS, thus resulting in Fe-catalyzed site-selectivity toward sp(3) C-H amination.

Automated summary

The computational study examined the mechanism and site-selectivity for Fe-catalyzed azaindoline formation from 1,2,3,4-tetrazole. It was found that the aliphatic H-atom abstraction (HAA) and electrophilic aromatic substitution (EAS) steps play a key role in determining the sp(3) vs. sp(2) C-H amination site-selectivity, with Fe-catalysis favoring sp(3) C-H amination due to steric congestion.