88292-20-0Relevant academic research and scientific papers
Photochemistry of 1,2-Diketones. Part 5. Formation of Dihydrodioxines, Oxetanes, Allylic Ethers, and 1,2-Adducts from Alicyclic 1,2-Diketones and Alkenes
Verheijdt, Paul L.,Cerfontain, Hans
, p. 1343 - 1349 (2007/10/02)
The photoaddition of five non-enolizing 1,2-diketones (1a-e), bipivaloyl, and biacetyl to various simple alkenes has been investigated.The dihidrodioxine formation dominates over the formation of oxetane, α-keto allylic ether, and 1,2-adduct (α-hydroxyketone) for three cyclic 1,2-diketones (1b-d) that have a syn-periplanar (lowest) excited 1,2-diketo configuration.The four-membered ring diketone (1a) photo-fragments prior to its addition to the alkene.Biacetyl with an anti-periplanar excited 1,2-diketo configuration does not form dihydrodioxines.No information on the geometry of the excited 1,2-diketo configuration could be obtained with (1e) and (2), as the rate of α-cleavage or intramolecular hydrogen abstraction of the anti-periplanar excited diketo moiety greatly exceeds the rate of reaction with the alkene.Thirteen dihydrodioxines, twelve oxetanes, four allylic ethers, and fourteen 1,2-adducts have been identified.The formation of the dihydrodioxine and oxetane formation has been discussed with special emphasis on (i) the nature of the reacting exciting state (the reacting state is the lowest triplet n-?* state of the 1,2-diketone), (ii) the intermediacy of exciplexes and 1,4-diradicals, and (iii) the stereospecificity of the dihydrodioxine and oxetane formation.
