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.