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[2 + 2] Photocycloaddition of Two Captodative Alkenes to 3‐Acetylthianaphthene
Author(s) -
Döpp Dietrich,
Hassan Alaa A.,
Henkel Gerald
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619960509
Subject(s) - chemistry , regioselectivity , adduct , thiophene , recrystallization (geology) , excited state , stereochemistry , crystal structure , crystallography , photochemistry , organic chemistry , paleontology , physics , nuclear physics , biology , catalysis
Abstract Photoexcited 3‐acetylbenzo[ b ]thiophene ( 1c ) adds 2‐morpholinopropenenitrile ( 2a ) in a [2 + 2] mode at the C2C3 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.