新しいチオフェン合成法の開発とその応用

Abstract

Intramolecular reductive carbonyl coupling of 3-thiapentane-1, 5-diones (diketo sulfides) with a low-valent titanium reagent, prepared from TiCl4 and Zn powder in THF, at 0°C or lower temperatures produces thiolanediols in good yields, while the reduction at room temperature or higher temperatures affords dihydro-thiophenes. The both compounds are converted to the corresponding thiophenes in high yields by acid-catalyzed dehydration or dehydrogenation with DDQ, thus providing a new thiophene synthesis. The new method is very versatile and allows the preparation of a wide variety of structurally interesting thiophenes, including highly congested 3, 4-di-t-butyl-, 3, 4-dineopentyl-, and 3, 4-di-1-adamantylthiophenes, angle-strained 1, 2, 4, 5-tetrahydrodicyclobuta [b, d] thiophene, parent “nonclassical” thienothiophene, and α, β-type thiophene oligomers. Conversion of the foregoing congested thiophenes to other congested molecules such as furan, pyrrole, selenophene, benzene, naphthalene, pyridazine, alkene, and thiete derivatives is described. Structural features of highly congested benzene derivatives are also touched. Finally, application to selenophene synthesis is described.