Photooxygenation of 3-acetyl-5-aryl-2-methylfurans via endoperoxide intermediate and the following reactions

• Published in: Tetrahedron Vol. 57; no. 28; pp. 6003 - 6009
• Main Authors: Onitsuka, Satoaki, Nishino, Hiroshi, Kurosawa, Kazu
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 09.07.2001; Elsevier
• Subjects: Chemistry; Chemistry, Organic; endoperoxide intermediate; photooxygenation; Physical Sciences; Science & Technology; UV irradiation; endoperoxide intermediate; UV irradiation; photooxygenation; CYCLIC PEROXIDE; BEHAVIOR; OZONOLYSIS; PHOTOSENSITIZED OXIDATION; FURAN ENDO-PEROXIDES; GENERAL-METHOD; CARBONYL OXIDE CHEMISTRY; SINGLET OXYGEN; MANGANESE(III); 2-ALKOXYFURANS
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/S0040-4020(01)00559-2

The photooxygenation of 3-acetyl-5-aryl-2-methylfurans 1a– e selectively produced 2,2-diacetyl-3-aroyloxiranes 2a– e, 3-acetyl-1-aryl-2-pentene-1,4-diones 3a– e, and 3-acetyl-1-aryl-2-hydroxy-2-pentene-1,4-diones 4a– d via the endoperoxide intermediate A depending on the reaction conditions and the work-up procedure. The oxiranes 2a– e were mainly obtained in 56–77% yields by allowing the reaction mixture to stand at ambient temperature after the irradiation, while the treatment of the reaction mixture with water mainly gave the 1,4-diones 3a– e (62–69%). Heating the reaction mixture at 80°C after the irradiation decreased the total yield of the products, however, the enols 4a– d were newly formed in 8–12% yields. Direct UV irradiation of the endoperoxide intermediate A led to the homolytic fission of the peroxide linkage to produce the same enols 4a– e (16–39%). The self-sensitized photooxygenation of 1a– d using a UV light also gave 4a– d in a similar yield. The reaction pathway is discussed based on these results. Graphic