Highly congested thiophenes, 3, 4-di-tert-butyl-, 3, 4-di (1-adamantyl)-, 3, 4-dineopentyl-, and 3-(1-adamantyl)-4-tert-butylthiophenes (4a-d), were prepared in satisfactory overall yields by intramolecular reductive coupling of 3-thiapentane-1, 5-diones (1a-d) followed by acid-catalyzed dehydration of the resulting thiolane-3, 4-diols (2a-d). Experimental procedures of this thiophene synthesis are fully described. Oxidation of the thiophenes 4a- ...
