Chiral Guanidine/Copper Catalyzed Asymmetric Azide‐Alkyne Cycloaddition/[2+2] Cascade Reaction

Abstract

We report the development of ac hiral guanidinebased copper(I) catalyst for the asymmetric azide-alkyne cycloaddition/[2+ +2] cascade reaction. Optically active spiroazetidinimine oxindoles were constructed by trapping the ketenimine species under mild reaction conditions.H igh level of enantioinduction and excellent isolated yields were achieved in the three-component reaction of various isatin-derived ketimines,s ulfonyl azides,a nd terminal alkynes.C ontrol experiments and X-ray crystallography were used to probe into the interaction of chiral guanidinium salt with copper salt. Scheme 1. Transformations beyond copper-catalyzed azide-alkyne cycloadditiono fN-sulfonyla zides.

Stereoselective synthesis and applications of spirocyclic oxindoles

“…99 In 2018, Liu advanced this type of reaction in a highly diastereoselective and enantioselective variant using a chiral guanidinium ligand L22 (Scheme 20B). 100 Azetidines from allene activation. The two main advances in the synthesis of spiroazetidine oxindoles (non-2-azetidinone structures) are from the Silvani lab in 2016 and 2017 involving allene activation.…”

Engaging Isatins in Multicomponent Reactions (MCRs) – Easy Access to Structural Diversity

“…This chiral guanidine/CuI complex traps the in situ generated ketenimines from azides and alkynes, affording a variety of spiroazetidinimine derivatives. The reaction had a remarkable scope and proceeded under mild reaction conditions [191] …”

“…Dinuclear Zn [45] CuI/DBU [51] CuSO 4 .5H 2 O [54] , [55] , [59] chiral guanidine/CuI [191] Ag(I)‐NHC complex [174] …”

Synthesis of [3.4]‐Spirooxindoles through Cascade Carbopalladation of Skipped Dienes

“…One of the factors influencing the biological activity of this type of compounds is the size of the ring that conforms the spirocyclic structure at the 3‐position of the oxindole moiety . In recent years, a plethora of synthetic methods giving rise to spirooxindoles with different substitution patterns has been reported in the literature . Thus it is possible to incorporate rings from 3 to 8 members at the 3‐position of the aforementioned nuclei.…”