2'-Hydroxyflavylium and 2'-hydroxyflavanone derivatives can be interconverted by a precise sequence of pH jumps, through the respective intermediate (mono) ionized trans-chalcones. In acidic and neutral media, the well known network of chemical reactions involving flavylium cation, quinoidal base, hemiketal, and cis and trans chalcones is established. In the pH range 8 < pH < 10, the chalcone (Ct) deprotonates and evolves to the formation of a flavanone (F). At higher pH values, the di-ionized trans-chalcone is the stable species, formed from the flavylium cation. Acidification of the di-ionized trans-chalcone gives the flavylium cation or the flavanone, via the mono-ionized trans-chalcone, respectively at pH < 1 and pH approximate to 9. In contrast with the chalcones, the flavanone once formed is stable even in acidic media. However, under strongly basic conditions, it leads back to the di-ionized trans-chalcone, the most stable species at more basic pH values, and the reactions leading to Ct(-), F, Ct(2-), Ct(-), constitute a one direction cycle for interconversion of these species.
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Petrov, Vesselin Diniz, Ana Marta Cunha-Silva, Luis Parola, A. Jorge Pina, Fernando
Pina, Fernando/C-8161-2011; Parola, A. Jorge/F-4048-2010; Cunha-Silva, Luis/A-8765-2012; REQUIMTE, AL/H-9106-2013
Parola, A. Jorge/0000-0002-1333-9076;
Fundacao para a Ciencia e Tecnologia through the National Portuguese NMR Network [PEst-C/EQB/LA0006/2011, PTDC/QUI-QUI/119932/2010]
This work was supported by Fundacao para a Ciencia e Tecnologia through the National Portuguese NMR Network, grant PEst-C/EQB/LA0006/2011 and project PTDC/QUI-QUI/119932/2010.
Royal soc chemistry
Cambridge