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Efficient Rhodium‐Catalyzed Installation of Unsaturated Ester Functions onto Porphyrins: Site‐Specific Heck‐Type Addition versus Conjugate Addition
Author(s) -
Baba Hiromi,
Chen Jinping,
Shinokubo Hiroshi,
Osuka Atsuhiro
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200701943
Subject(s) - conjugate , chemistry , rhodium , porphyrin , catalysis , heck reaction , polymer chemistry , acrylate , conjugated system , photochemistry , organic chemistry , palladium , copolymer , polymer , mathematical analysis , mathematics
A facile introduction of α,β‐ or α,β,γ,δ‐unsaturated ester functions onto porphyrins was achieved through rhodium‐catalyzed addition of β‐borylporphyrins to acrylate or 2,4‐pentadienoate esters. The reaction of meso ‐borylporphyrins with acrylates exclusively afforded saturated esters by 1,4‐conjugate addition under the same reaction conditions. Thus, the reaction mode (Heck‐type versus conjugate addition) is highly dependent on the reaction site (β versus meso ). This functionalization has a significant impact on the electronic properties of the π system of porphyrins, which induces a substantial redshift and broadening in the absorption spectra by effective conjugation through the β positions. The coplanar structure of the unsaturated ester moieties with respect to the porphyrin core has been unambiguously elucidated by X‐ray crystallographic analysis.