Study On TBHP/TBAI-Mediated Synthesis Of Substituted Diaminoalkenes

Diaminoalkenes are important structures which present biology activities and pharmacological activities. Cross-coupling reactions between an sp2 carbon of an arene or alkene and N-moiety represent the most adopted approaches in building N-containing compounds in modern organic chemistry. Herein we developed a metal-free cross-coupling of enamines and electron-deficient amines through oxidative C(sp2)-N bond formation has been realized by using TBAI as catalyst and TBHP as oxidant. This novel strategy allows for an efficient organocatalytic synthesis of the synthetically useful diaminoalkene derivatives which could be further converted to 4-aminoisoxazole and 2H-azirine. The methodology is highlighted by appealing features such as readily available of the starting materials, wide substrate scope and transition-metal-free characteristics.Various enamines 220 and electron-deficient amines 221 as the substrates were performed in NMF under 100 oC in the TBHP/TBAI system to provide 27 diaminoalkene derivatives. The enamines include ester enamines, eneminones and N-substituted enamines while the electron-deficient amines involve phthalimide, succinimide, 4-nitrophthalimide, 1H-benzimidazole, 1,2,4-1H-triazole and benzotriazole. All the novel compounds have been well characterized by 1H NMR, 13 C NMR, HRMS and melt points. Besides, compound 222 d was also confirmed by X-ray crystallography.Meanwhile, a plausible mechanism of the TBHP/TBAI-mediated oxidative cross-coupling reaction of enamines and electron-deficient amines was proposed. The key oxidative species are tetra-n-butylammonium hypoiodite and tetra-n-butylammonium formed from TBHP/TBAI.