摘要
发展了一种温和、高效的以腙为配体的铜催化系统,在相对温和的条件下,将该系统用于催化胺与芳卤的N-芳基化反应,得到了良好的分离收率.腙配体是稳定的、价廉的,并易于通过简单的方法,从市场可得的原料制备.
The synthesis of compounds containing the N-aryl moiety has attracted a great deal of interest recently due to the importance of such compounds in fields as diverse as natural products, photograph, and materials. How- ever, two major factors that hamper application are the cost and the availability of the catalysts, in particular of the ligands that are often prepared in a tedious multi-step synthesis. Therefore, the discovery of more cost-effective and highly efficient ligands is still critically desirable. For this reason, we has embarked on a program aimed at the de- velopment of ligands that are low-cost and easily prepared in few steps from readily available starting materials. First, the hydrazone and oxime ligands were prepared from inexpensive, commercially available starting materials （ i. e. azanol and hydrazine） by using a simple method. Secondly, the coupling reaction of phenyl iodide with morpholine was used as model reaction using K3PO4 as base in the presence of CuBr under mild reaction temperature of 95℃ in DMSO. A variety of synthesized hydrazone and oxime ligands were respectively used for the coupling of morpholine with phenyl iodide. The best result was obtained when 2-thiofuranformaldehyde-N-methylphenyl- hydrazine（ 4a ） was utilized as ligand. Thirdly with optimal ligand 2-thiofuranformaldehyde-N-methylphenyl- hydrazine（4a） and above model, frequently used bases（such as K3PO4, K2CO3, KOH, KOBu＇, NaOBu＇, Cs2CO3 and NEt3 ） , solvents（ e. g. DMSO, DMF, dioxane, toluene, CH3 CN, THF） and copper sources （for example Cu-Br, CuCl, CuI, Cu2O, CuCN） were respectively screened. It was proved that Cs2CO3 was the best among opti- mized bases and a survey determining the influence of the solvent with Cs2CO3 as base showed that the model reaction could be efficiently conducted in DMSO. The air-stable, inexpensive Cu2O was the most efficient among the examined copper sources. Finally, the optimized optimal catalytic system Cu2O/2-thiofuranformaldehyde-N-methyl- phenylhydrazine （4a）/Cs2CO3/DMSO was further extended to the N-arylation of other amines with aryl iodides, 5- bromopyrimidine and 2-bromopyridine under relative mild condition and good yields were obtained. Although this protocol is restricted to the coupling of highly activated aryl halides, these favorable characteristics make them po- tentially practical utility in many cases and represent an advance toward the discovery of simple, low-cost catalyst systems for eventual availability.
出处
《分子催化》
EI
CAS
CSCD
北大核心
2016年第5期420-427,共8页
Journal of Molecular Catalysis(China)
基金
中央高校自主科研基金(DC201501020201)
关键词
胺
芳卤
腙
N-芳基化
amine
aryl halide
hydrazone
N-arylation
