Mechanistic Insights into Enantioselective CH Photooxygenation of Aldehydes via Enamine Catalysis. Issue 9 (7th May 2015)

• Record Type: Journal Article
• Authors: Walaszek, Dominika J.; Rybicka‐Jasińska, Katarzyna; Smoleń, Sabina; Karczewski, Maksymilian; Gryko, Dorota
• Is Part Of: Advanced synthesis & catalysis. Volume 357:Issue 9(2015)
• Page Start: 2061
• Page End: 2070
• Publication Date: 2015-05-07
• Subjects: Catalysis -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Chemistry -- Periodicals; Chemistry, Technical -- Periodicals; Chemistry -- Periodicals; Catalysis -- Periodicals; Technology, Pharmaceutical -- Periodicals; 547.2
• DOI: 10.1002/adsc.201500056
• Languages: English
• ISSNs: 1615-4150

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Organocatalytic photooxygenation of aldehydes at the α‐position proceeds <italic>via</italic> enamine catalysis, though enamines should be easily oxidized by singlet oxygen respectively to amides and carbonyl compounds. Moreover, the formation of a zwitterionic enamine peroxide intermediate was postulated based on experimental and theoretical data. The reaction affords desired diols (after in situ reduction) in a decent yield and (<italic>S</italic>)‐ or (<italic>R</italic>)‐enantioselectivity depending on a catalyst used. The (<italic>S</italic>)<italic>‐</italic>enantiomer predominated in imidazolidinone‐catalyzed reactions, while prolineamides assured the formation of the (<italic>R</italic>)‐stereoisomer. DFT calculation suggests that the enamine–oxygen complex with the lowest energy has the <italic>E, </italic> <italic>s</italic>‐<italic>cis</italic> conformation for the prolineamide derivative and <italic>E, </italic> <italic>s</italic>‐<italic>trans</italic> for the imidazolidinone catalyst, explaining the opposite stereoselectivity in the photooxygenation reaction.</p> <p> <graphic position="anchor" mimetype="image" xlink:href="ark:/27927/pgj10cp21kb" orientation="portrait" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /> </p> </abstract>