Method for preparing 2,2'-dimethylbiphenyl

Abstract

The invention provides a method for preparing 2,2'-dimethylbiphenyl. The method comprises the following steps: mixing NiCl2(TPP)2, o-chlorotoluene, tetrahydrofuran, magnesium, a nitrogenous co-ligand, an initiator, i.e., iodine, and the like, heating the mixture to a reaction temperature, adding a mixed solution of o-chlorotoluene and tetrahydrofuran to the mixture, and carrying out a reaction, thereby obtaining 2,2'-dimethylbiphenyl. According to the method, firstly, a Grignard reagent is produced in an in-situ manner in a reaction process, so that a subsequent reaction can be carried out directly without synthesizing the Grignard reagent in advance, reaction steps are reduced, the operation is relatively simple, the production cycle is shortened, and the requirements of industrial production are met; and meanwhile, the nitrogenous co-ligand is added during the in-situ production of the Grignard reagent, so that the conversion ratio and selectivity of a coupling reaction are improved. Shown by experimental results, the selectivity of the 2,2'-dimethylbiphenyl prepared by the method provided by the invention can reach 76% to 97%, and the raw-material conversion ratio can reach 85% to 99%.

Description

technical field [0001] The invention belongs to the technical field of organic synthesis, and in particular relates to a preparation method of 2,2'-dimethylbiphenyl. Background technique [0002] The formation of C-C bonds is an important way to form carbon skeletons in organic synthesis, and the coupling of Grignard reagents with halogenated hydrocarbons under transition metal catalysis is an important method for forming C-C bonds. As early as the 1970s, Kochi and Tamura [TamuraM, Kochi J.K.J.Am.Chem.Soc[J], 1971,93:1487-1489] studied a series of halogenated hydrocarbons and Grignard reagents on Ni, Pd, Fe Couplings catalyzed by other transition metals, such as Kumada and Corriu first independently reported NiCl in 1972 2 Coupling of Grignard reagents under (dppp) catalysis and sp2 hybridized halogenated hydrocarbons [Tamaok, Sumitanik, Kumada, M, J.Am.Chem.Soc.[J], 1972,94:4374-4376], Ni-based catalysts have a good effect on the coupling of bromine- and iodine-substitute...

AI Technical Summary

Problems solved by technology

In the process of using Ni-Zn catalyst to prepare 2,2′-dimethylbiphenyl, although the conversion rate and selectivity are as high as 94.7% and 93.4%, the preparation procedure of Ni-Zn catalyst is cumbersome, the conditions are harsh, and the reaction time is long. up to 14 hours

In the Grignard reagent method, the Grignard reagent is first prepared, refluxed for 18 hours, and then gradually added to the catalyst containing NiCl 2 (TPP) 2 And in the mixed system of raw material 2-chlorotoluene and tetrahydrofuran, further react for 4 hours, the selectivity of target product can reach 93%, but the yield is low, only 68%, and solvent THF consumption is big in the reaction process, needs deoxygenation and Metal sodium benzophenone dehydration treatment, the process is cumbersome and takes a long time, and a large amount of toluene is used as the extraction agent in the post-treatment

The prior art also discloses the catalytic synthesis of 2,2′-dimethylbiphenyl (M.Sahin, etal.Polyhedron, 30(2011), 2051-2054) with a nitrogen-containing ligand nickel complex, using o-chlorotoluene as Raw material, part of the raw material first generates the corresponding Grignard reagent with metal magnesium, and then catalyzes coupling with o-chlorotoluene to prepare 2,2′-dimethylbiphenyl, but the conversion rate is low, only 47.1%

Images