Preparation of toluenes specifically labelled with C-14

The attempt to prepare toluene-2 C-14 starting from ethyl acetoacetate failed because the reaction of sodium ethyl acetoacetate with dibromopropane could not be performed. This labelling was also attempted starting from methyl tetrahydropyran. This synthesis was not successful because the preparationof 2-methyl pimelic acid was impossible. Labellimg of carbon-3 of toluene starting from succinic acid could not be carried out because the Grignard reaction of a-ketoglutaric acid as unsuccessful. The radioactive syntheses started from propanediol resp. from c-butyrolactone. (The labelling of carbon-3 of toluene was not possible in this case because the reduction of malonic acid to propanediol could not be carried out). The synthesis course was identical for all labellings. The synthesis differed only in the introduction of the activiy from potassium cyanide C-14. The starting compounds were reacted to propanedinitril, which was saponified to glutaric acid. The acid was reduced to pentanediol. From the diol, dibromopentane was produced. Reaction with potassium cyanide yielded, after saponification, pimelic acid. The acid was cyclizated to cyclohexanone, which was reduced to cyclohexanol. The OH group was replaced by bromine and subsequently by a methyl group. Dehydration yielded toluene. The following labellings were carried out: Toluene-2, -2.6, -1.2.6, -1.2 C-14. (G.G.)