The STOBBE Condensation, Part IX. The cyclisation of (E)-3-Methoxycarbonyl-4-(5′-methyl-2′-thienyl)-but-3-enoic acid, and α,β-bis-(5-methyl thenylidene)-succinic anhydride, to benzothiophen derivatives

✍ Scribed by Dr. S. M. Abdel-Wahhab (Mrs.); Dr. N. R. El-Rayyes

• Book ID: 105351828
• Publisher: John Wiley and Sons
• Year: 1971
• Tongue: English
• Weight: 360 KB
• Volume: 313
• Category: Article
• ISSN: 1615-4150
• DOI: 10.1002/prac.19713130208

✦ Synopsis

Abstract

The condensation of 5‐methyl‐thiophen‐2‐aldehyde with dimethyl succinate in the presence of potassium t‐butoxide or sodium hydride gave predominantly (E)‐3‐methoxy‐carbonyl‐4‐(5′‐methyl‐2′‐thienyl)‐but‐3‐enoic acid 1a, whose configuration is proved by cyclisation with sodium acetate in acetic anhydride to the corresponding benzothiophen derivatives 2. Alcoholysis of the derived (E)‐carboxy‐4‐(5′‐methyl‐2′‐thienyl)‐but‐3‐enoic anhydride 3 gives the half‐ester 1c which is isomeric with the half‐ester 1a. Condensation also gave the α,β‐bis‐(5‐methyl thenylidene)‐succinic acid 4a in small amounts. The derived anhydride 5 yields on pyrolysis 4‐(5′methyl‐2′‐thienyl)‐2‐methyl‐benzothiophen‐5,6‐dicarboxylic anhydride 6.