Regiodivergent Synthesis of 4,5′- and 4,4′-Imidazolinyl Spiropyrazolones from 4-Alkylidene Pyrazolones and Amidines
Hui Xu, Ran Hong, Ming-Yue Weng, Ronglu Huang, Guan‐Wu Wang, Ze Zhang
Abstract
The solvent-free reaction of 4-alkylidene pyrazolones with amidines can furnish 4,5′-imidazolinyl spiropyrazolones in good to excellent yields when promoted by N-iodosuccinimide under solvent-free ball-milling conditions, whereas it almost exclusively affords 4,4′-imidazolinyl spiropyrazolones if mediated by N-bromosuccinimide in heated toluene. On the basis of this switchable cyclization strategy, a powerful metal-free method for regioselective and diastereoselective synthesis of structurally diverse 4,5′- and 4,4′-imidazolinyl spiropyrazolones has been successfully developed.
Topics & Concepts
PyrazolonesChemistryRegioselectivityTolueneSolventCombinatorial chemistryBall millOrganic chemistryReaction conditionsCatalysisChemical engineeringEngineeringSynthesis and Catalytic ReactionsCatalytic C–H Functionalization MethodsSynthesis of heterocyclic compounds