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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… Click to show full 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.
Journal Title: Organic letters
Year Published: 2021
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