A new synthesis of [14C]-PD-117302 has been described: The Reformatsky condensation of 4,5,6,7-tetrahydrobenzo[b]thiophen-4-one (II) with methyl [1-14C]-bromoacetate (I) by means of Zn in reflux toluene gives a mixture of methyl [1-14C]-2-(4,5,6,7-tetrahydrobenzothiophen-4-ylidene)acete (III) and methyl [1-14C]-2-(6,7-dihdyrobenzothiophen-4-yl)acetate (IV) which, without separation, are treated with Pd/C and S in refluxing N-methylpyrrolidone to afford methyl [1-14C]-2-(benzothiophen-4-yl)acetate (V). The hydrolysis of (V) with methanolic KOH yields the corresponding acid (VI), which is treated with refluxing SOCl2 to give the acyl chloride (VII). Finally, this compound is condensed with trans-1-[2-(methylamino)cyclohexyl]pyrrolidine (VIII) in dichloromethane ethyl ether.