Dimetallation of m-Xylene

a -dimetallation of m-xylene (and presumably also of o-xylene, but not of p-xylene (compare Ref. [3]) can be achieved in a convenient way using commercially available reagents. 

We have also carried out the procedures described by Bates and co-workers [3] a mixture of m-xylene, 2.2 equivalents of finely powdered t-BuOK, 2.2 equivalents of BuLi and hexane was heated under reflux for 2.5 h, then THF and excess of Me3SiCl were successively added with cooling below 0 °C. After a very sluggish reaction (heating to 30-35 °C was necessary) the expected a,a -disilylated derivative was obtained in 60% yield. Shorter periods of reflux (1 h, as mentioned by Bates) gave mainly the mono-silyl derivative. 

5 Lithiation of Toluene, Xylene, and Mesitylene with BuLi TMEDA 

Subsequent reactions with dimethylformamide, dimethyldisulfide, methyl isothiocyanate, carbon dioxide, trimethylchlorosilane, paraformaldehyde, cyclohexyl bromide, and bromoacetaldehyde diethylacetal. 

Apparatus For the metallation a 500-ml round-bottomed, three-necked flask is used, equipped with a gas-inlet, a mechanical stirrer, and a reflux condenser, connected with a washing bottle filled with parrafin oil (the inner tube should not dip more than 0.5 cm into the oil). All connections are made gas-tight. For the functionalizations the apparatus is modified as indicated below. 

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