Net-1,2-Hydrogen Atom Transfer of Amidyl Radicals: Toward the Synthesis of 1,2-Diamine Derivatives
Yonggang Jiang, Dongxiang Liu, Madeline E. Rotella, Guogang Deng, Zhengfen Liu, Wen Chen, Hongbin Zhang, Marisa C. Kozlowski, Patrick J. Walsh, Xiaodong Yang
Abstract
Hydrogen atom transfer (HAT) processes are among the most useful approaches for the selective construction of C(sp 3 )–C(sp 3 ) bonds. 1,5-HAT with heteroatom-centered radicals (O •, N • ) have been well established and are favored relative to other 1, n -HAT processes. In comparison, net 1,2-HAT processes have been observed infrequently. Herein, the first amidyl radicalls are reported that preferentially undergo a net 1,2-HAT over 1,5-HAT. Beginning with single electron transfer from 2-azaallyl anions to N -alkyl N -aryloxy amides, the latter generate amidyl radicals. The amidyl radical undergoes a net-1,2-HAT to generate a C-centered radical that participates in an intermolecular radical–radical coupling with the 2-azaallyl radical to generate 1,2-diamine derivatives. Mechanistic and EPR experiments point to radical intermediates. Density functional theory calculations provide support for a base-assisted, stepwise-1,2-HAT process. It is proposed that the generation of amidyl radicals under basic conditions can be greatly expanded to access α-amino C-centered radicals that will serve as valuable synthetic intermediates.