In the presence of a catalytic amount of active titanium(IV) salt or Y
b(OTf)(3), weakly nucleophilic anilines and indole react under mild co
nditions with formic acid or aqueous formic acid to afford respectivel
y the corresponding formanilides and indole-3-carboxaldehyde in excell
ent yields using 4-trifluoromethylbenzoic anhydride as a coreagent.