Density Functional Theory Study of the Mechanisms of Iron-Catalyzed Aminohydroxylation Reactions

Experimental
studies recently show that iron salts are effective
catalysts for oxaziridine-mediated oxyamination reactions, in place
of the powerful osmium-catalyzed Sharpless aminohydroxylation method.
The present study reports a theoretical analysis of the mechanism
of the iron-catalyzed aminohydroxylation reaction between vinylbenzene
and N-sulfonyloxaziridine substrate using density
functional theory (DFT) calculations. Our calculations show that the
Fe­(II)-catalyzed process is favored over the Fe­(III)-catalyzed process
for the overall catalytic cycle. The rate-limiting step in the whole
catalytic cycle is the process of forming the final aminohydroxylation
product from a six-membered-ring intermediate, but the solvation effect
in MeCN of this step leads to a lowering of the energy barrier computed
using the C-PCM method. The regioselectivity has also been investigated.