Process for the preparation of pure aryllithium compounds and their use

Abstract

A process is described for preparing aryllithium compounds by reaction of metallic lithium in an ether-containing solvent with an aryl halide, wherein prior to or at the beginning of the reaction a catalyst is added, the catalyst containing a halogen-free, polynuclear aromatic (aryl catalyst) or consisting of such a compound.

1 . Process for the preparation of aryllithium compounds by the reaction of metallic lithium in an ether-containing solvent with an aryl halide, characterised in that, prior to or at the beginning of the reaction, a catalyst is added, the catalyst containing a halogen-free, polynuclear aromatic (aryl catalyst) or consisting of such a compound.  
     
     
         2 . Process according to  claim 1 , characterised in that the aryl catalyst used is a polynuclear, halogen-free aromatic selected from the group of ortho-condensed aromatics or from the group of aromatics bonded to one another by single bonds, the aromatic possibly being alkyl-substituted or possibly containing a functional group.  
     
     
         3 . Process according to  claim 2 , characterised in that naphthalene, phenanthrene, anthracene, diphenyl or 4,4′-di-tert. butyldiphenyl is used as the aryl catalyst.  
     
     
         4 . Process according to one of  claims 1  to  3 , characterised in that the aryl catalyst is added in a quantity of 0.05 to 2 mol. % (based on the total quantity of aryl halide used).  
     
     
         5 . Process according to one of  claims 1  to  4 , characterised in that the metallic lithium is in finely-divided form, having particle sizes of <0.1 mm, and is dispersed in the solvent.  
     
     
         6 . Process according to one of  claims 1  to  5 , characterised in that the lithium metal has an Na content of 0.5 to 5 wt. %.  
     
     
         7 . Process according to one of  claims 1  to  6 , characterised in that an excess of 1 to 40 mol. % lithium to aryl halide is used.  
     
     
         8 . Process according to one of  claims 1  to  7 , characterised in that acyclic ethers R—O—R′ where R and R′ independently of one another each have 1 to 6 C atoms, or cyclic ethers having 4 to 8 C atoms, individually or in a mixture, are used as the ether-containing solvent.  
     
     
         9 . Process according to one of  claims 1  to  8 , characterised in that diethyl ether, dipropyl ether, dibutyl ether, tert. butyl methyl ether, tert. amyl methyl ether, tetrahydrofuran, 2-methyltetrahydrofuran or tetrahydropyran, individually or in a mixture, is used as the ether-containing solvent.  
     
     
         10 . Process according to one of  claims 1  to  9 , characterised in that the ether-containing solvent contains, in addition, anhydrous hydrocarbons in a quantity of 50 wt. % at most, based on the total quantity of solvent.  
     
     
         11 . Process according to one of  claims 1  to  10 , characterised in that a drying agent is added to the lithium metal suspension prior to the addition of the aryl halide.  
     
     
         12 . Process according to one of  claims 1  to  11 , characterised in that the temperature of the reaction (addition stage and post-reaction stage) is −20° C. to +100° C.  
     
     
         13 . Process according to one of  claims 1  to  12 , characterised in that the aryl halide used is a halobenzene and the ether-containing solvent used is dibutyl ether and that phenyllithium is obtained as product.  
     
     
         14 . Process according to  claim 13 , characterised in that the ether-containing solvent contains another ether in addition to dibutyl ether.  
     
     
         15 . Process according to one of  claims 1  to  12 , characterised in that the aryl halide used is a halobenzene and the ether-containing solvent used is dibutyl ether in a mixture with cyclohexane or methylcyclohexane and that phenyllithium is obtained as product.  
     
     
         16 . Use of the aryllithium compounds prepared by a process according to one of  claims 1  to  15  as reagents in organic synthesis.