Abstract: | An efficient synthesis of [1‐13C]‐para‐xylene ( 1a ) and [2‐13C]‐para‐xylene ( 1b ) is described. The incorporation of the label has been achieved by cyclocondensation of suitable 1,5‐bis(bromomagnesio)alkanes with either ethyl [1‐13C]acetate or ethyl [13C]formate which gave [ring‐13C]‐labelled dimethylcyclohexanols. Dehydration of these alcohols followed by dehydrogenation of the intermediate dimethylcyclohexenes furnished the title compounds in 32 and 40% overall yield, respectively. Copyright © 2001 John Wiley & Sons, Ltd. |