An improved synthesis of [1‐14C]‐labelled 2‐butynedioic acid, succinic acid and succinyl chloride

The reaction of [14C]CO2, generated from [14C]BaCO3, with dilithio propiolate (2) at −78°C afforded [1- 14C]-2-butynedioic acid (3) Reduction of 3 with platinum oxide and hydrogen gas gave [1-14C]-succinic acid (4) in 74% overall radiochemical yield from [14C]BaCO3 with a specific activity of 55.4 mCi/mmol (2.05 GBq/mmol). Reaction of 4 with dichloromethyl methyl ether in the presence of zinc chloride yielded [1-14C]-succinyl chloride (5, 97.5% radiochemical yield).