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The reaction of n-BuLi for extracting bromine and introducing the n-butyl group belongs to the combined process of halogen-lithium exchange and nucleophilic substitution, and it usually occurs in aryl or alkenyl bromides.
### **Reaction Mechanism**
1. **Halogen-Lithium Exchange**: n-BuLi reacts with organic bromides (such as bromobenzene) to form aryl lithium (ArLi) and bromo-n-butane (n-BuBr).
2. **Nucleophilic Addition**: The newly formed ArLi acts as a strong nucleophile and attacks n-BuBr (or additional halogenated hydrocarbons) in the system, forming a new C-C bond and obtaining the n-butyl-substituted product (Ar-nBu).
### **Main Applications**
- **Alkylation of Aryl/Alkenyl Groups**: Used for constructing complex organic molecules (such as drugs, material monomers).
- **Good Functional Group Compatibility**, but requires low temperature (-78℃) operation to avoid side reactions (such as Wurtz coupling).
