Palladium-Catalyzed Cyclization of N-Acyl-o-alkynylanilines with Isocyanides Involving a 1,3-Acyl Migration: Rapid Access to Functionalized 2-Aminoquinolines

Abstract

A simple and expedient approach for the synthesis of functionalized 2-aminoquinolines via palladium-catalyzed annulation of N-acyl-o-alkynylanilines with isocyanides has been developed with high atom economy, in which an unconventional 6-endo-dig cyclization process is observed. Further investigations of the mechanism demonstrated that an intramolecular acyl migration of the N-protecting groups was involved in this transformation.

MOF-based Pd catalysts: a controllable and efficient platform towards cyclization reactions of isonitriles

“…Combining the experimental results and previous works, 25 we propose that Pd(OAc) 2 in the UiO-67-bpy support undergoes three main stages to generate the product 3 (Scheme 2): (i) the de-intercalation stage, where Pd( ii ) species first falls off from UiO-67-bpy into solution and coordinates with 1a to form intermediate A ; (ii) the catalytic stage, where many micro-homogeneous catalytic systems are constructed centered on MOF supports to achieve the smooth generation of intermediate B via 1,1-migration insertion of 2a ; and finally (iii), the self-healing stage, when B undergoes anti-carbopalladation of alkynes directly with the assistance of another Pd( ii ) species to afford product 3a , the generated Pd( ii ) species would be eventually captured by free coordination sites in the MOF, a process similar to ships moored on the dock, that could efficiently circumvent the generation of Pd(0) species and further precipitation of Pd black. As for the process of producing the product 4 , we supposed that the Pd species would go through a similar catalytic cycle, except for the reductive elimination process.…”

Annulation of 2‐Alkynylanilines: The Versatile Chemical Compounds

“…N ‐acyl‐ o ‐ethenylaniline gave the lowest yield of the corresponding product (Scheme 26). [76] Wang et al . achieved same product via different reagents; they treated 2‐ethynylanilines with alkyl nitriles in the presence of CuCl 2 /ClCF 2 CO 2 Na catalytic system [77] …”

“…N-acyl-o-ethenylaniline gave the lowest yield of the corresponding product (Scheme 26). [76] Wang et al achieved same product via different reagents; they treated 2-ethynylanilines with alkyl nitriles in the presence of CuCl 2 /ClCF 2 CO 2 Na catalytic system. [77] Cu(II)-catalyzed oxidative cyclization of compound 8 with methyl perfluoroalk- peroxycopper(III) 83, rearrangement of the latter, and finally cleavage of the peroxycopper(II) complex 85.…”

Recent Advances in Palladium-Catalyzed Isocyanide Insertions

“…Another report communicated a similar synthesis of 2-aminoquinoline from N -trifluoroacetylated ortho -alkynylanilines 322 and isocyanides [ 138 ]. In this study, the authors postulated that amination of the Pd II catalyst is followed by isocyanide insertion, generating intermediate imidoyl palladium species 324 , which is η 2 -bonded with the alkyne ( Scheme 86 ).…”