A method for the preparation of [3'-3H]-4-(2'-chloro-6'- hydroxyphenyl)-2-thioxo-3,4-dihydro-1H-indeno[1,2-d]pyrimidin-5 (2H)-one (1), a TRPA1 inhibitor, was developed for the evaluation of imaging properties of a class of TRPA1 inhibitors. 1 was prepared via tritiation of a protected benzaldehyde followed by a tetrachlorosilane catalyzed multicomponent one-step fusion and was obtained at a specific activity of 0.9 TBq/mmol. A 3H-NMR spectrum on 13.5MBq at 75 μM was recorded.