115077-66-2Relevant articles and documents
Preparative UV-VIS Laser Photochemistry: Photocycloadditions of Methylenelactones with Benzophenone and p-Benzoquinone. Oxygen Trapping of Paterno-Buechi Triplet 1,4-Diradicals as Model Reactions for Quinghaosu-Type 1,2,4-Trioxanes
Adam, Waldemar,Kliem, Ulrike,Lucchini, Vittorio
, p. 869 - 876 (2007/10/02)
The UV-VIS laser irradiation of 4-penten-4-olide (1) with benzophenone (BP) or with p-benzoquinone (BQ) under an argon atmosphere afforded the acetal-type oxetanes 2-BP and 2-BQ, respectively.Only for BP was the oxetane regioisomer 3-BP obtained, actually as major product, while 3-BQ appears to be photolabile under VIS-laser photolysis conditions and thus does not accumulate in sufficient amounts for detection.Under an oxygen atmosphere, besides these oxetane products also the 1,2,4-trioxanes 5-BP and 5-BQ, the oxygen trapping products of the intermediary preoxetanetriplet diradicals 12, were isolated and fully characterized.These results demonstrate that spirolactone-type 1,2,4-trioxanes as quinghaosu analogues are accessible via trapping of Paterno-Buechi triplet 1,4-diradicals by molecular oxygen.In the case of diketene as enol-lactone partner, the Paterno-Buechi reaction with BQ gave a complex product mixture even under an argon atmosphere, leading to the oxetane 6 as major product, and the spirocyclobutanone 7 and spirobioxetane 8 as minor products.Under an oxygen atmosphere also the spiroacetal 9 was obtained, but no trioxanes (oxygen trapping) could be detected in this VIS-laser photolysis.
