[2 + 2] Photocycloaddition of Two Captodative Alkenes to 3-Acetylthianaphthene

✍ Scribed by Döpp, Dietrich ;Hassan, Alaa A. ;Henkel, Gerald

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 432 KB
• Volume: 1996
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.199619960509

✦ Synopsis

Abstract

Photoexcited 3‐acetylbenzo[b]thiophene (1c) adds 2‐morpholinopropenenitrile (2a) in a [2 + 2] mode at the C2C3 bond regioselectively but stereounselectively with formation of cyclobuta[b][1]benzothiophenes 3a and 4a. In addition, the isomeric adduct 5 is formed from 2a and excited 2‐acetylbenzo[b]thiophene (1b) accompanying 1c as an impurity. Similarly, 2‐(tert‐butylthio)propenenitrile (2b) undergoes a smooth and highly regioselective but stereounselective [2 + 2] photoaddition to 1c yielding a mixture of two isomeric adducts from which compound 3b may be separated by recrystallization. The configuration of 5 was unambiguously confirmed by an X‐ray crystal structure analysis. The structures of the other cycloadducts were derived by a comparison of their ^1^H‐NMR spectral data with those of closely related substances from other work.