Reduction of bis(5-alkyl-2-furyl)(2-nitroaryl)methane with aqueous titanium trichloride solution

Abstract In this article, we introduces a new method for the synthesis of substituted indole by reductive recyclization of bis(5-alkyl-2-furyl)(2-nitroaryl)methane. Bis(5-alkyl-2-furyl)(2-nitroaryl)methane undergo reduction to provide indole or aniline. In the process of research, we found that the chemoselecitivity of reduction was controlled by subtle differences in the electronic effects of the substrate. Mechanistic studies reveal the origin of this chemoselectivity. Our results suggest the two pathways share common nitroxide ion intermediate. Electron donating groups on aromatic ring promote direct reductive from this intermediate to afford aniline product. Alternatively, electron withdrawing groups on aromatic ring enable furan ring opening from nitroxide ion intermediate to generate the indole product.