Study On Ligand-Free Copper/Iron Cocatalyzed C-N Cross-Coupling Reactions In Air

C(aryl)-N bond has always been a common subunit in many biologically active natural products, dyes, pharmaceuticals, and functional materials,and thus synthesis method of C(aryl)-N bond is critical in synthetic organic chemistry. Transition metal catalyzed C-N cross-coupling reaction is one of the most straightforward and efficient strategy for the formation of C(aryl)-N bond. Compared with other transition metals, copper and iron are inexpensive and harmfulless, therefore, they are usually used as catalysts in organic reactions. In this dissertation, we have developed two simple, efficient, green and inexpensive Ullmann reaction systems using Cu/Fe as cocatalysts. The two ligand-free protocols are insensitive to atmospheric moisture and oxygen,and neither dried solvent nor an inert atmosphere is required.1. A protocol has been developed for the N-arylation of aqueous dimethylamine with aryl bromides. The coupling of4-bromoacetophenone and aqueous dimethylamine was selected as the model reaction to investigate the effect of solvents,catalysts, bases and reaction time on this reaction. The optimized conditions were as follows:CuBr(20mol%)/Fe(acac)3(20mol%) as the cocatalysts, Na2CO3(2.0equiv) as the base, and DMSO(2.0mL) as the solvent,90℃,18h, air. It is noteworthy that aryl bromides containing electron-withdrawing groups show higher reactivity than those containing electron-donating groups. The steric hindrance also exerted great influence on the coupling reaction. and the reactions of para-or meta-substituted aryl bromides affored higer yields than steic ortho-substituted aryl bromides. The results demonstrated that the reacivity order of substituted aryl halides:para-> meta-> ortho-.2. A catalyst system has been developed for the N-arylation of sulfamides or amides with arly halides. The coupling of p-toluenesulfonamide and iodobenzene was chose as the model reaction to investigate the effect of solvents,catalysts, and bases on this reaction. The optimized conditions were as follows:CuCl(20mol%)/Fe(acac)3(20mol%)(for the N-arylation of sulfamide) or Cul(20mol%)/Fe(acac)3(20mol%)(for the N-arylation of amide) as the cocatalysts, Cs2CO3(2.0equiv) as the base, and DMF(2.0mL) as the solvent,90℃,24h, air. This method afforded good to excellent yields, and exhibited better functional gronp tolerance.