Abstract
The multistep flow synthesis of vinyl azides and their application in the synthesis of vinyltriazoles is reported. The synthesis relies on a stable polymer-bound equivalent of iodine azide that serves to carry out 1,2-functionalization of alkenes in a telescope flow protocol. The intermediate 2-iodo azides are subjected to a DBU-mediated polymer-supported elimination step yielding vinyl azides in good yield. The third step involves the formation of vinyl triazoles by a copper-catalyzed Huisgen-"click" cycloaddition. The required heat is generated by electromagnetic induction based on copper. Copper serves both as heatable as well as catalytically active packed-bed material inside the flow reactor.
Highlights
Azides are highly versatile organic functional groups and their preparation and their reactivity are well explored [1]
Yu et al [2] disclosed the synthesis of pyrazoles, while Chiba et al employed vinyl azides for the Mn(III)-mediated synthesis of different azaheterocycles [3,4]
For the first time we present the coppermediated Huisgen-type “click” cycloaddition of vinyl azides with alkynes to yield vinyl triazoles under inductive-heating conditions
Summary
Azides are highly versatile organic functional groups and their preparation and their reactivity are well explored [1]. We disclose the first two-step flow synthesis of vinyl azides based on functionalized polymers 5 and 8. Scheme 3: Two-step protocol for the preparation of vinyl azides 4a–e and 4g–i under flow conditions.
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