Direct N–H/α,α,β,β-C(sp<sup>3</sup>)–H functionalization of piperidine<i>via</i>an azomethine ylide route: synthesis of spirooxindoles bearing 3-substituted oxindoles
A protocol for the direct functionalization of N-H/[small alpha],[small alpha],[small beta],[small beta]-C(sp3)-H of piperidine without any metal or external oxidants is reported. These reactions are promoted by 4-(trifluoromethyl)benzoic acid via an azomethine ylide intermediate....