Photo-ring contraction reactions of 4-hydroxypyrylium cations

✍ Scribed by James W. Pavlik; Alfred P. Spada

• Book ID: 104237961
• Publisher: Elsevier Science
• Year: 1979
• Tongue: French
• Weight: 232 KB
• Volume: 20
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)86613-2

✦ Synopsis

4-Hydroxypyrylium cations undergo photo-ring contraction upon irradiation of 50 percent H~SOI,. Dihydroxycyclopentenones are intermediates in these reactions. A variety of 4-hydroxypyrylium cations are known to undergo photoisomerization in concentrated H~SOI, to yield 2-hydroxypyrylium cations.

la-f In one example, however, this photo-trans.

position reaction was accompanied by a photo-ring contraction. Thus, irradiation of 2,3-di-