Hydrogenation of Simple Thiophens

Desulphurization and Hydrogenation of Simple Thiophens. - The reduction of (137) with seven equivalents of lithium in ethylamine at —20°C gave 

LiAlH4, gave (138) upon reaction with five equivalents of lithium, 

A modified method for the synthesis of (139) has been described. Birch reduction of 2-acylthiophens and of 2-acyl 5-alkylthiophens, followed by alkylation with alkyl halides, gave 2-acyl-, 2-alkyl-, or 2-acyl-2,5-dialkyl-thiophens in good yields. Oxidation of these compounds to the 1,1-dioxides by MCPBA, followed by thermolysis, offers a convenient route to 1,3-dienyl ketones. The Birch reduction of 2-t-butyl-5-pivaloylthiophen to the corresponding 2,5-dihydrothiophen was a key procedure in the synthesis of 

6-di-t-butyl-4-methylthiopyrylium salts.Birch reduction of (140) was used for the synthesis of (141).The technical importance of the removal of thiophens from oil and coal has led to a great number of papers on catalytic dehydrosulphurization.  

Kosugi, A. V. Anisimov, H. Yamamoto, R. Yamashiro, K. Shirai, and T. Kumamoto, Chem. Lett., 1981, 1341. 

---

Desulphurization and Hydrogenations of Simple Thiophens. -Thiophen and several alkylthiophens have been desulphurized by... 

---