Cycloaddition reactions. A new type of cycloadduct from a substituted 2-vinylthiophen and dmad

✍ Scribed by Belen Abarca; Rafael Ballesteros; Concepcion Soriano

• Book ID: 104205099
• Publisher: Elsevier Science
• Year: 1987
• Tongue: French
• Weight: 580 KB
• Volume: 43
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(01)90036-5

✦ Synopsis

Cycloaddition reactions between 2-(1-cyanoallyl)thiophen and the dienophiles diethyl azodicarboxylate, N-phenylmaleimide , methyl propiolate,and dimethyl acetylenedicarboxylate are reported. Products include simple benzo[b]thiophen carboxylates (13,19) and reduced derivatives (8,9,10,12,18), as a mixture of diastereoisomers, except in the adduct with diethyl azodicarboxylate. With dimethyl acetylenedicarboxylate a new type of tricyclic compound was also found (20).

We have previously reported, that 2-vinylthiophen' and 3-vinylthiophen' react with a number of simple dienophiles to give a variety of products, which include benzo[b]thiophencarboxylates and reduced derivatives, with a pattern of substituents unavailable by other routes. With acetylenic dienophiles, dimethyl acetylenedicarboxylate and methyl propiolate, 2-vinylthiophen gives also the dithienylcyclohexene esters (1) and ( 2). This type of product is unique in reported cycloaddition of simple vinylheterocycles, and were not formed in the similar reactions with 3-vinylthiophen. In this case also two new types of 2:l adducts (3) and (4) were obtained in the reaction with methyl propiolate.

The presence of substituents in the vinyl group of the vinylthiophens WR:E

(3) (4) (2)R :H