Efficient Magnesium Bromide-Catalyzed One-pot Synthesis of Substituted 1,2,3,4-Tetrahydropyrimidin-2-ones Under Solvent-free Conditions

Anefficientandenvironmentallyfriendlyprocedurefortheone-potsynthesisoftetrahydropyrimidinonesfromaldehydes,β-diketonesandurea/thioureabyusingmagnesiumbromideasaninexpensiveandeasilyavailablecatalystundersolvent-freeconditionswasdescribed.ComparedwiththeclassicalBiginellireactionconditions,thisnewmethodhastheadvantageofgoodtoexcellentyields(74%-94%)andshortreactiontime(45-90min).ThestructureoftheBiginellireactionproductfromβ-diketone,salicylaldehydeandureahasbeenproposedtopossessanoxygen-bridgebycyclization(intramolecularMichael-addition).