Study on Synthesis of ortho-Hydroxyl Aromatic N-tert-Butylsulfinyl Imines under Microwave Irradiation

Chiral N-tert-butanesulfinyl imines have been shown to be important intermediates for asymmetric synthesis in recent years. Eleven new (R,E)-N-(2-hydroxybenzylidene)-tert-butyl-sulfinamides (3) were synthesized from salicylaldehydes 1 and chiral tert-butanesulfinamide 2 under microwave irradiation in moderate to good yields. The reaction could work well in the mixture of KHSO4/PhMe or Cs2CO3/CH2Cl2. And the results show that the KHSO4/PhMe reaction system is helpful for the salicylaldehydes with electron-donating group; however, the Cs2CO3/CH2Cl2 reaction system is applicable to the salicylaldehydes with electron-deficient group and steric hindrance group. The structures of these new compounds were determined by H-1 NMR, C-13 NMR, IR and HRMS.