Copper-Catalyzed Oxidative Condensation Into N-Sulfinylimines And N-Sulfonylimines

N-sulfinyl-and N-sulfonylimines are a kind of important intermediates in organic synthesis.The new protocols for the copper-catalyzed aerobic oxidative condensation of alcohols with sulfinamides or sulfonamides into N-sulfinyl-and N-sulfonylimines with the promotion of ligands have been developed to resolve the problems existing in the field of the synthesis of N-sulfinyl-and N-sulfonylimines currently.The emploment of L-proline makes the oxidations of aromatic primary alcohols,allyl alcohols and heterocyclic aromatic alcohols into the corresponding aldehydes,subsequently,condense with aromatic or aliphatic sulfin-and sulfonamides to afford N-sulfinyl-and N-sulfonylimines with high yields and selectivity in organic phase,using molecular oxygen?air?as the terminal oxidant.Firstly,the effects of the combination of N,O-bidentate ligands amino acids with copper in the oxidative condensation of alcohols with sulfinamides were explored.By systematic screening the various of natural amino acids,functionalized amino acids,nitrogen-containing compounds,copper catalysts,solvents,reaction temperature,the optimum reaction conditions are obtained as: alcohols?1.0 mmol?,sulfinamides?1.0 mmol?,CuI?5 mol%?,TEMPO?5 mol%?,L-proline?5 mol%?,K₂CO₃?0.5 mmol?,toluene?4.0 mL?,4? MS?700 mg?,60 oC.Under the optimal conditions,this system shows excellent functional groups compatibility for a wide range of substrates and affords the corresponding products efficiently.In addition,the pure chiral sulfonamides were also tolerated with high values of enantionmeric excesses.Based on the related published researches,a possible reaction mechanism is proposed.Subsequently,amino acids are selected as an effective N,O-bidentate ligand to evaluate the effects of the copper-catalyzed aerobic oxidative condensation of alcohols and sulfonamides in organic phase.In this paper,a series of solvents,copper salts,ligands,bases are systematic screened.A new method of aerobic oxidative condensation for the synthesis of N-sulfonylimines with L-proline as ligand,copper salt as catalyst,TEMPO as auxiliary oxidant,air as the terminal oxidants.Under the optimal conditions,a series of aromatic alcohols aerobic oxidative condense with aromatic,heterocyclic aromatic,aliphatic sulfonamides to afford the corresponding sulfonylimine compounds.