Radical-Transfer Hydroamination of Olefins with N-Aminated Dihydropyridines

An efficient synthesis of N-phthalimidyl, benzamidyl, acetamidyl, carbamoyl, and ureayl derivatives of dihydropyridines and the application of these reagents as precursors for N-centered radicals are presented. These aminated dihydropyridines could be used in radical-transfer hydroamination reactions of various electron-rich as well as nonactivated olefins in the presence of thiols as polarity-reversal catalysts. These reactions worked without the aid of any transition metal. Steric and electronic effects exerted by the N-substitutents of the N-centered radicals are discussed. In contrast to most metal-catalyzed processes, the radical hydroamination delivered the opposite regioisomer with excellent anti-Markovnikov selectivity. Hydroamination products were obtained as protected amines that are readily isolated.