T. Mathew et al., PHOTOTRANSFORMATIONS OF 9-ETHYL-SUBSTITUTED DIBENZOBARRELENE, Journal of photochemistry and photobiology. A, Chemistry, 95(2), 1996, pp. 137-141
Photolysis of benzoyl-9,10-dihydro-9-ethyl-9,10-ethenoanthracene (1) i
n benzene or acetone in the complete absence of oxygen gives the 4b-et
hyl-substituted dibenzosemibullvalene (5) (45-48%) whereas, in the pre
sence of oxygen, 1 in acetone gives a mixture of 5 (32%), together wit
h two oxygenated products, namely the peroxy compound 12 and the lacto
ne 20. The structures of 5,12 and 20 have been confirmed through singl
e-crystal X-ray diffraction studies. Compound 5 arises through a di-pi
-methane rearrangement of 1, whereas 12 is formed through the oxygen q
uenching of a diradical intermediate, derived from an isomeric 8b-ethy
l-substituted dibenzosemibullvalene (6). Compound 20 arises through th
e oxygen quenching of a diradical intermediate, implicated in the phot
orearrangements of 1,2-dibenzoylalkenes.