prov:value
| - it being possible to use hydrocarbons, such as toluene and xylene, further ethers, such as dibutyl ether, tetrahydrofuran, dioxane, glycol dimethyl ether and diglycol dimethyl ether, additionally polar solvents, such as dimethyl sulphoxide, sulpholane, dimethylformamide and N-methyl-pyrrolidone, and, only in the case in which compounds of the formula (VI) are employed, alcohols such as methanol, e
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