Changing one chemical element to another usually requires fusion (like in stars).
There is also a possibility of "cold fusion", done by chemical reaction, not high-energy heat. And apparently that is achieved already? Not lead to gold, and not producing power, but changing one element to another anyway...
"Carl and Richard dive into the most controversial aspect of fusion power, so-called "cold fusion." This is a sensitive topic in the scientific community, so much so that it's name changes on a regular basis. The current popular name is Low Energy Nuclear Reactions"
Toyota researchers confirmed that nuclear changes from one element to another took place without the use of high-energy nuclear physics."