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Synthesis and Photochemistry of syn ‐ and anti ‐9,10‐Epoxy‐1, 4‐dihydro‐1,4‐ethanonaphthalene‐2,3‐diones
Author(s) -
Liao ChunChen,
Hseu TzongHsiung,
Lin HoShen,
Tang ChiaPin,
Ueng YihGang,
Wang JinnLung,
Wann GwoHuei,
Wu KuanSyh
Publication year - 1991
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.199100044
Subject(s) - chemistry , steric effects , cis–trans isomerism , saponification , yield (engineering) , stereochemistry , epoxy , quantum yield , photodissociation , nmr spectra database , spectral line , photochemistry , medicinal chemistry , organic chemistry , materials science , physics , quantum mechanics , metallurgy , fluorescence , astronomy
Abstract The title epoxydiketones were prepared stereoselectively, direct epoxidation of 3a‐c with MCPBA produced syn isomers la‐c whereas epoxidation of 4a‐d followed by saponification of the spirolactone rings gave anti isomers 2a‐c. The stereochemistry of 1a and 2a was established by X‐ray diffraction, whereas that of the remaining epoxydiketones was determined from the correlation of visible, 1 H, and 13 C NMR spectral data; the differences between spectra of the corresponding syn and anti isomers are explained in terms of through‐space interaction and steric effects. Photolysis of syn isomers 1a‐c afforded the corresponding naphthalenes 8a‐c in almost quantitative yields; in contrast, irradiation of anti isomers 2a‐c gave complicated mixtures. The quantum yield of disappearance of 1a was 52 times that of 2a. Reaction mechanisms are proposed to account for the product formation. The differences in the photochemical behavior of the title syn and anti isomers are rationalized in terms of stereoelectronic effects of the epoxy rings in the syn isomers.