AQUEOUS HIGH-TEMPERATURE CHEMISTRY OF CARBOCYCLES AND HETEROCYCLES .17. THIOPHENE, TETRAHYDROTHIOPHENE, 2-METHYLTHIOPHENE, 2,5-DIMETHYLTHIOPHENE, BENZO[B]THIOPHENE, AND DIBENZOTHIOPHENE

The title compounds are unaffected under both thermolysis and neutral aquathermolysis conditions up to 350-degrees-C. In the presence of 10% phosphoric acid, thiophene gave tetrahydrothiophene and 2-methylthiophene as major products along with other mono-, di-, and trimethylthiophenes, and di-and trithienyl derivatives as minor products. 2-Methylthiophene afforded 2,4- and 2,7-dimethylbenzothiophenes as major products in addition to di- and trithienyl derivatives. 2,5-Dimethylthiophene is very reactive and furnished several mono- and disubstituted methyl-, ethyl-, propyl-, and butylthiophenes in appreciable amounts. Benzothiophene gave several higher molecular weight products by desulfurization, by Diels-Alder reaction, and by dimerization processes. Tetrahydrothiophene and dibenzothiophene showed no reaction, even at 350-degrees-C for 5 days with 10% phosphoric acid.