Aryl halides arylzinc compound electrochemical

The formation of arylzinc reagents can also be accomplished by using electrochemical methods. With a sacrificial zinc anode and in the presence of nickel 2,2-bipyridyl, polyfunctional zinc reagents of type 36 can be prepared in excellent yields (Scheme 14) . An electrochemical conversion of aryl halides to arylzinc compounds can also be achieved by a cobalt catalysis in DMF/pyridine mixture . The mechanism of this reaction has been carefully studied . This method can also be applied to heterocyclic compounds such as 2- or 3-chloropyridine and 2- or 3-bromothiophenes . Zinc can also be elec-trochemically activated and a mixture of zinc metal and small amounts of zinc formed by electroreduction of zinc halides are very reactive toward a-bromoesters and allylic or benzylic bromides . ... 

Mechanism of the electrochemical conversion of aryl halides to arylzinc compounds by nickel catalysis5 45... 

After the electrochemical preparation of ZnBr2 and the introduction of both 0 2 and aryl halide, it was seen that arylzinc compounds were detected in small amounts without engaging electricity. This phenomena was interpreted as follows the zinc stemming from electroreduction of ZnBr2 can reduce cobalt(II) hahde to form low-valent cobalt Co(I), which can activate aryl bromides to form arylzinc compounds via ArConX. The mechanism would be similar to that proposed by the electrochemical approach. In this case, the reduced zinc becomes reactive and can replace electricity. From this electrochemical... 

The formation of arylzinc reagents can also be accomplished by using electrochemical methods. With a sacrificial zinc anode and in the presence of nickel 2,2-bipyridyl, polyfunctional zinc reagents of type 5 can be prepared in excellent yields (Equation (5)). An electrochemical conversion of aryl halides to arylzinc compounds can also... 

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