Synthesis of 14C‐labelled bromocresol green and metacresol purple

[methyl-14C]-Bromocresol green 1 was synthesized from [14C] - methyl iodide in four steps via 3-[methyl-14C]-methylanisole 3, [methyl-14C]-metacresol 4 and [methyl-14C]-metacresol purple 6. The overall yield of 1 from [14C] methyl iodide was 5.3% and the specific activity 112 mCi/mmol.