We provide a detailed description of plausible mechanism about IPrAgBr- or IPrAuBr-catalyzed 2-methyl-N-methoxyaniline to obtain multisubstituted aniline[1-2]. This work mainly discusses the rearrangement of methyl and methoxy groups, and hydrogen shift to restore the aromaticity of the benzene via theoretical study. The calculation results show that the [1,3]-methoxy rearrangement in the IPrAgBr catalytic system is the rate-determining step in the entire reaction pathway with energy barrier of ∆G‡= 29.5 kcal·mol-1, and hydrogen transfer go through a total barrier of ∆G‡= 28.6 kcal·mol-1. While the result is different from IPrAuBr catalyzed system ([1,3]-methoxy rearrangement ∆G‡= 28.4 kcal·mol-1; hydrogen shift ∆G‡= 30.5 kcal·mol-1). Here, the multisubstituted products are different from IPrCuBr catalyzed system, resulted from the unstable Ag(III) and Au(III) intermediates. From our computational results, the IPrAg or IPrAu complex is involved in the entire process, whereas substrate-assisted hydrogen shift to restore the aromaticity in the later part can be proceeded without Cu catalyst.
multisubstituted aniline;[1,3]-methoxy rearrangement;theoretical calculation