The synthesis and spectroscopic characterisation of chiral meso-tetraarylmetalloporphyrins bearing meso-pentafluorophenyl groups

Abstract

The successful synthesis of 5,10,15,20-tetrakis[(R,R)-2,6-bis(1-phenylbutoxy)phenyl]porphyrin, with (R)-1-phenylbutoxy substituents on each of the eight ortho-positions, by a 2ϩ2 approach via meso-[(R,R)-2,6-bis(1-phenylbutoxy)phenyl]dipyrromethane rather than a one-pot condensation of (R,R)-2,6-bis(1-phenylbutoxy)benzaldehyde with pyrrole, is described. The synthesis has also been modified using meso-(pentafluorophenyl)dipyrromethane to prepare four further chiral porphyrins containing one, two (cis and trans) and three pentafluorophenyls in place of the bis(phenylbutoxy)phenyl groups. The cross-coupling of the two dipyrromethanes with pentafluorobenzaldehyde gave as one of the products the unexpected cis-disubstituted 5,10-bis(pentafluorophenyl)-15,20-bis[(R,R)-2,6bis(1-phenylbutoxy)phenyl]porphyrin. It seems likely that the formation of the latter compound involves the acidcatalysed reversion of the dipyrromethane synthesis. Both faces of each of the porphyrins are chiral and equivalent in this way the wasteful formation and time-consuming separation of atropisomers is avoided. Four iron() and one manganese() complex of these porphyrins have been prepared. The 1 H and 19 F NMR spectra of the series of porphyrin ligands reveal some interesting structure-and symmetry-dependent splitting patterns and trends which are used to confirm the identities of the compounds. In particular, the 1 H NMR couplings of the β-pyrrole hydrogens are very diagnostic of the substitution patterns of the meso-aryl groups on the porphyrin ring.

Nucleophilic Aromatic Substitution on Pentafluorophenyl‐Substituted Dipyrranes and Tetrapyrroles as a Route to Multifunctionalized Chromophores for Potential Application in Photodynamic Therapy

“…However, in addition to the desired A 2 B 2 ‐porphyrins, other porphyrin byproducts were formed as a result of “scrambling” . In fact, for the dipyrrane substrates 2b and 10a , the byproducts were formed in larger amounts than the desired product (Table , entries 1 and 5).…”

“…Condensation reaction of functionalized dipyrranes to trans-A 2 B 2 -porphyrins (A = PFP substituent, B = R-tetrafluorophenyl substituent). However, in particular for the two amino-substituted dipyrranes in addition to the desired A 2 B 2 -porphyrins, other porphyrins were formed as by-products due to 'scrambling´, [36,37] for the dipyrranes 2b and 10a in amounts larger than the desired product (Table 3, entries 1 and 4). This observation is in accordance with a recent publication by Arunkumar and coworkers who also observed large amounts of scrambling products in the condensation reaction of 5-(4-cyanophenyl)-dipyrrane and 8a with BF 3 ·OEt 2 as catalyst.…”

Chiral porphyrin imine manganese complex as catalyst for asymmetric epoxidation of styrene derivatives

“…27 Aerobic enantioselective alkene epoxidation catalyzed by chiral trans-dioxo (D4-porphyrinato) ruthenium (VI) complex was also reported. 31 Boitrel et al reported the asymmetric epoxidation of styrene derivatives and naphthalene derivatives using two different series of bisstrapped chiral iron porphyrin complexes derived from L-prolinoyl residues as catalysts. 29 A new family of porphyrin metal complexes based on chiral atropisomerism was reported as catalysts for the enantioselective epoxidation of styrene derivatives.…”

“…30 In the year 2001, Foxon et al reported the synthesis of porphyrins by mixed condensation of pyrrole, (R,R)-2,6di(1-phenylbutoxy) benzaldehyde, and pentafluorobenzaldehyde. 31 Boitrel et al reported the asymmetric epoxidation of styrene derivatives and naphthalene derivatives using two different series of bisstrapped chiral iron porphyrin complexes derived from L-prolinoyl residues as catalysts. 32 In the year 2004, Nakagawa et al described an efficient synthesis of novel D4-symmetric chiral porphyrins and used them as catalysts in asymmetric epoxidation reaction.…”

Synthesis and characterization of new soluble polyfluorinated seco-porphyrazines

“…Also, fluorocarbons display enhanced hydrophobicity, chemical resistance and thermal stability in comparison to their hydrocarbon counterparts [43,52]. Consequently, porphyrazines reported here can be proposed as active compounds for catalytic and photosensor applications in homogeneous media [17,18,53]. …”