I use the method shown in the picture or a similar method, such as dropping methyllithium into cuprous iodide to get Gilman's reagent, and then add the substrate；or use a different Grignard reagent.

The substrate is quickly consumed and the only product is formed which Rf＞0.9(PE as eluent). 1H NMR shows that this product has a complex structure not my target product. Has anyone encountered the same problem and how to solve it.