Concomitant (3 + 3) Annulation/Fragmentation of Triazinanes with Enamines: Electrosynthesis of Multisubstituted Dihydropyrimidines

An electro-oxidative formal (3 + 3) annulation of 1,3,5-triazinanes with enamines toward multisubstituted 1,2-dihydropyrimidines is reported. This metal-free mild protocol offers wide functional group tolerance, and heterocycles with an unexplored molecular scaffold were constructed in excellent yields. Mechanistically, the electro-oxidation of triazinane and nucleophilic reactivity of enamine result in a concomitant annulation-fragmentation process, leading to the six-membered heterocyclic product.