Abstract
New reaction conditions were investigated for dialkylizing diethyl 3,4-dihydroxy-2,5-thiophenedicarboxylate with sterically hindered alkyl-dibromides, using as reaction system DMF–trialkylamine or only the trialkylamine as base–solvent. This methodology produced the corresponding 3,4-cycloalkoxy-2,5-diethoxycarbonyl-thiophene derivatives faster and with better yields than those reported previously for K 2CO 3–DMF. Experiments were performed with triethylamine, tripropylamine, and tributylamine. Tributylamine produced the best results in a general reaction with alkyl-bromides. Aromatic amines like N, N-dimethylaniline, N-methyldiphenylamine, and triphenylamine failed to react at all. Reactions using only the tributylamine as base–solvent demonstrated that DMF is not necessary as a solvent to obtain good yields.
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