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Tetraphenylporphyrin‐Catalyzed Tandem Photooxygenation of Polyenes and 1,4‐Dienes: Multiple and Diverse Oxyfunctionalizations
Author(s) -
Griesbeck Axel G.,
de Kiff Alan,
Kleczka Margarethe
Publication year - 2014
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201400565
Subject(s) - chemistry , photooxygenation , singlet oxygen , allylic rearrangement , regioselectivity , tetraphenylporphyrin , photochemistry , ene reaction , epoxide , catalysis , cycloaddition , cycloisomerization , diene , medicinal chemistry , oxygen , organic chemistry , porphyrin , natural rubber
Tandem singlet oxygen reactions photocatalyzed by meso ‐tetraphenylporphyrin were performed with substrates designed for primary α‐ gem ‐selectivity or high vinylogous gem ‐selectivity. The 1,3,5‐triene ester 1 was designed as a model compound for the natural compound crocin and resulted in a highly regioselective singlet oxygen ene reaction with ε‐hydrogen activation (93:7 ene vs. [4+2] cycloaddition). The initially formed hydroperoxide 2a adds another singlet oxygen molecule in a slower reaction step to furnish the endoperoxide 3a . From the hydroperoxide stage, oxygen transfer gives the epoxide 4 , reduction leads to the allylic alcohol 2b and subsequent photooxygenation (to 3b ) followed by reduction results in the furan derivative 5 . The allylic alcohol could also be reacted with other dienophiles as shown for the PTAD adduct 6 . From the 1,4‐diene 7 , a gem ‐regioselective singlet oxygen ene reaction generates a mixture of the hydroperoxides 8a and 9a . Product 8a adds another singlet oxygen molecule to give the endoperoxide 10a . Catalyst activity was demonstrated by analysis of the changes in the electronic absorption properties.