Electron transfer chain reactions in systems containing carbon-nitrogen double bonds

摘要

Free radical chain reactions of imines and iminium salts with tert-butylmercury halides give reductive alkylation products. Promotion of the electron transfer step in these electron transfer processes by protonation or silylation of the imines has been demonstrated. [alpha]-Arylthiyl or [alpha]-alkylthiyl amines undergo photostimulated reactions with alkylmercury halides to produce the [alpha]-aminoalkyl radicals, which are subsequently oxidized to the iminium salts and undergo reductive alkylation in the presence of KI. Imines only give additive (reductive) alkylation products with t-BuHgCl. Azaaromatic compounds can give either additive or substitutive products. Benzimidazoles give only the substitutive product while acridine gives only the additive product. Quinolines, isoquinolines and benzothiazole can give either reductive or oxidative alkylation depending upon the conditions. The intermediacy of dihydro derivatives has been established in the substitutive (oxidative) alkylation of pyridines, quinolines and isoquinolines. Acid catalysis is observed in the reductive alkylations of acridine, quinoline and isoquinoline by t-BuHgCl/KI. With quinalidine, the intermediate 4-tert-butyl dihydro derivative undergoes methylation at C-3 with methyl iodide to form a stable 3,4-dihydroquinoline derivative;Photolysis of PhNC with t-BuHgCl/KI in Me[subscript]2SO forms PhNHCOCMe[subscript]3. Electron transfer from PhN=C(CMe[subscript]3)· to t-BuHgX is postulated to occur. 1,2-Benzenedicarboximides produce substitutive ortho alkylation products in high yields upon photostimulated reaction with t-BuHgCl in the presence of Dabco (1,4-Diazabicyclo (2.2.2) octane) or with KI/K[subscript]2S[subscript]2O[subscript]8. Anilines and phenols produce Pummerer-type products in the presence of Dabco, t-BuHgCl and KI in Me[subscript]2SO.