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Photochemische Reaktionen. 107. Mitteilung. Zur Photochemie offenkettiger 2,6‐bzw. 2,7‐Dien‐Carbonylverbindungen
Author(s) -
Yoshioka Michikazu,
Ishii Keitaro,
Wolf Hans Richard
Publication year - 1980
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19800630305
Subject(s) - chemistry , isomerization , ketone , medicinal chemistry , intramolecular force , diene , photochemistry , yield (engineering) , citral , acetaldehyde , stereochemistry , organic chemistry , catalysis , ethanol , natural rubber , materials science , chromatography , essential oil , metallurgy
The Photochemistry of Open‐Chained 2,6‐ or 2,7‐Dien‐Carbonyl Compounds On 1 n , π*‐excitation (λ > 347 nm) citral (5) and the methyl ketone 10 isomerize to compounds A (7, 19) and B (6, 20) , whereas the phenyl ketone 11 changes into the isomer 24 of type E. Evidence is given that the conversions to A and B may arise from the 3 n , π*‐state of the 2,6‐diene‐carbonyl compounds. On 1 n , π*‐excitation (λ = 254 nm) 5 and 10 yield the isomers A (7, 19) and D (18, 22) , but no products of type B. Furthermore, conversion of 10 to the isomer 21 of type C is observed. Selective 1 n , π*‐excitation (λ = 254 nm) as well as selective 1 n , π*‐excitation (λ > 347 nm) of the 2,7‐diene‐carbonyl compounds 12 and 13 give rise to isomerization to the compounds F (25, 28) , exclusively. The intramolecular [2 + 2]‐photocycloadditions are shown to be triplet processes. UV.‐irradiation (λ > 280 nm) of compounds F (25, 28) furnishes the isomeric products G (26, 29) which photoisomerize to oxetanes of type H (27, 30).