prov:value
| - anhydride, acid halide, ester or amide, e g at temperatures between 0??? and 250??? C. but preferably at the boiling temperature of the reaction mixture, optionally in the presence of a condensing agent such as phosphorus oxychloride, thionylchloride, sulphurylchloride, sulphuric acid, p-toluenesulphonic acid, methanesulphonic acid, hydrochloric acid, phosphoric acid, polyphosphoric acid, acetic a
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