Hydrogen-bond activation enables aziridination of unactivated olefins with simple iminoiodinanes

Abstract

Iminoiodinanes comprise a class of hypervalent iodine reagents that is often encountered in nitrogen-group transfer (NGT) catalysis. In general, transition metal catalysts are required to effect efficient NGT to unactivated olefins because iminoiodinanes are insufficiently electrophilic to engage in direct aziridination chemistry. Here, we demonstrate that 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) activates N-arylsulfonamide-derived iminoiodinanes for the metal-free aziridination of unactivated olefins. 1H NMR and cyclic voltammetry (CV) studies indicate that hydrogen-bonding between HFIP and the iminoiodinane generates an oxidant capable of direct NGT to unactivated olefins. Stereochemical scrambling during aziridination of 1,2-disubstituted olefins is observed and interpreted as evidence that aziridination proceeds via a carbocation intermediate that subsequently cyclizes. These results demonstrate a simple method for activating iminoiodinane reagents, provide analysis of the extent of activation achieved by H-bonding, and indicate the potential for chemical non-innocence of fluorinated alcohol solvents in NGT catalysis.