Photosensitized oxidation of acetylenes

✍ Scribed by N. Berenjian; P. de Mayo; F.H. Phoenix; A.C. Weedon

• Book ID: 104237916
• Publisher: Elsevier Science
• Year: 1979
• Tongue: French
• Weight: 223 KB
• Volume: 20
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)86537-0

✦ Synopsis

The sensitized (electron transfer) photo-oxidation of acetylenes to yield benzils is described and the mechanism is discussed. We have recently reported2y3 the results of our investigations into the valence tautomerism between cr-dithiones, Ia, and 1,2-dithietes, IIa, and between a-ketothiones, Ib, and 1,2-oxathietes IIb, and the existence of these systems led us to consider the possibility of observing the corresponding valence isomers of a-diketones, Ic, i.e. 1,2-dioxetes, 11~. Apart from early reports", not confirmed5, no evidence had been presented for the existence of 1,2-dioxetes, IIc, until Turro reported the oxidation of a strained acetylene both with ground state and singlet oxygen, the results of which could be rationalized with the intermediacy of a dioxete6. However, oxygen does not normally add to acetylenes, though Foote has demonstrated that singlet.oxygen will add to electron rich triple bonds'. We have confirmed that simple acetylenes do not react with singlet oxygen generated by methylene blue or rose bengal sensitization in methanol.8