Imagine that you want to make chlorobenzene with a carbon-14 label in one site only, the only site you want it to be in is on the carbon bearing the chlorine. Can you think of a better and shorter synthesis from a labelled C1 compound such as methyl iodide or barium carbonate ? The literature method is
BaCO3 --> CO2 --> Acetic acid --> Ethyl acetate
Next react with pent-1,5-diyl magnesium bromide to form 1-methylcyclohexan-1-ol
Dehydrate to 1-methylcyclhex-1-ene, dehydrogenate with palladium to toluene, convert to benzoic acid with an oxidant, use sodium azide and acid to make aniline. Last use nitrous acid and copper(i) chloride on the aniline to make the chlorobenzene. I count ten reactions.
My suggestion is to react labeled nitromethane with formaldehyde Then dehydrate to make nitroethene Use the nitroethene for a Diels-Alder reaction with furan Dehydrate with an acid to make labeled nitrobenzene Reduce with hydrogen and palladium on carbon to make aniline React thw aniline with nitrous acid to form the diazonium salt Convert the diazonium salt with copper(I) chloride to the target molecule.
This is seven steps, can anyone come up with a shorter synthesis ?