This solvent is exemplified by ethers such as ethyl ether, isopropyl ether, tetrahydrofuran and dioxane, aromatic hydrocarbons such as benzene, toluene and xylene, N,N-dimethylformamide (DMF), halogenated hydrocarbons such as chloroform and dichloromethane, pyridine and dimethyl sulfoxide, chosen as appropriate according to the kind of electrophilic reagent.