Improved Method for the Synthesis of Dialkyl-substituted Thiophene 1, 1-Dioxides |
| |
Authors: | W J M van Tilborg |
| |
Institution: | Koninklijke/Shell-Laboratorium , Shell Research B.V. , Amsterdam |
| |
Abstract: | Abstract The peracid oxidation of substituted thiophenes to thiophene 1, 1-dioxides has been extensively investigated by Melles and Backer1,2. Most oxidations, especially those of 3,4-disubstituted thiophenes, afford the sulfones in fair to good yields. Oxidation of 2,5-dimehtylthiophene, however, only yields 14% of the corresponding dioxide. As we needed considerable amounts of this dioxide and related compounds for oxidation studies3 and the preparation of cyclo-heptatrienes4, we had to improve the method of its synthesis. We found that using the commercially available m-chloroperbenzoic acid as the oxidant, freezing out (?55 °C) most of the m-chlorobenzoic acid formed and subsequently removing the residual acid with the aid of tert-amino-substituted macroreticular resins, the yield could be increased considerably (Table I). An additional advantage of using the above-mentioned ion-exchange resins is that they decompose any excess of the peracid. This procedure was also successfully applied to the synthesis of other 2,5- or 2,4-disubstituted thiophene 1,1-dioxides (see Table I). |
| |
Keywords: | |
|
|