Are there alternatives to Axitinib Impurity 4 (CAS: 1443118-73-7) in synthesis?

While Axitinib Impurity 4 (CAS: 1443118-73-7) is a specific compound, there are alternative impurities and reagents that can be used in synthesis processes. For example, using other axitinib impurities or different starting materials can provide alternative routes. However, the choice of alternative reagents should be guided by the specific requirements of the synthesis and regulatory compliance.