Metal-Free Molecular Editing of Indole C−H Bonds via a Sequence of
Tandem Reaction
Abstract
A practical molecular editing strategy has been established for the
direct and consecutive C-3 diazenylation and C-2 arylation of indoles
with aryltriazenes under metal-free and ambient conditions. A sequence
of tandem reactions has been developed via the sustained release of
aryldiazonium species from aryltriazenes to achieve the controlled
multiple bonds sequential cleavage and formation. This strategy enables
the regio- and chemo-controlled consecutive C−H functionalization of
indole at two adjacent reactive sites (C-2 versus C-3) without
pre-functionalization of the reactive sites and even without the
assistance of the directing group, metal catalyst or ligand. Detailed
mechanistic experiments and DFT calculations along with supported a
sequence of tandem reaction mechanisms. The synthetic importance of this
methodology is evident from the simple operation, good functional group
tolerance, gram-scale synthesis, late-stage modification of
pharmaceuticals and in vitro cytotoxicity evaluation.