Density Functional Theory Study of the Mechanisms of Iron-Catalyzed Intramolecular C-H Amination [1,2]-Shift Tandem Reactions of Aryl Azides

摘要

The mechanisms of iron(II) bromide-catalyzed intramolecular C-H bond amination [1,2]-shift tandem reactions of aryl azides have been studied using density functional theory calculations. The tandem reaction from R-1, 1-azido-2-(1-methoxy-2-methylpropan-2-yl)benzene, to produce P-2, 2,3-dimethyl-1H-indole, was calculated. Our results showed that the overall catalytic cycle includes the following steps: (I) extrusion of N-2 to form iron nitrene; (II) C-H bond amination; (III) formation of the middle product P-1, 2-methoxy-3,3-dimethylindoline; (IV) iminium ion formation ; (V) [1,2]-shift process; and (VI) formation of indole P-2. The rate-limiting step is the [1,2]-shift process, where the energy barrier Delta E = 28.7 kcal/mol in the gas phase. Our calculated results also indicated that the preference for the [1,2]-shift component of the tandem reaction is methyl < ethyl.