Fluorinated Porphyrin Tweezer:  A Powerful Reporter of Absolute Configuration forerythroandthreoDiols, Amino Alcohols, and Diamines

Abstract

A general and sensitive nonempirical protocol to determine the absolute configurations of erythro and threo diols, amino alcohols, and diamines is reported. Binding of diols to the porphyrin tweezer system is greatly enhanced by increasing the Lewis acidity of the metalloporphyrin. Supramolecular complexes formed between the porphyrin tweezer host and chiral substrates exhibited exciton-coupled bisignate CD spectra with predictable signs based on the substituents on the chiral center. The working model suggests that the observed helicity of the porphyrin tweezer is dictated via steric differentiation experienced by the porphyrin ring bound to each chiral center. A variety of erythro and threo substrates were investigated to verify this chiroptical method. Their absolute configurations were unequivocally determined, and thus a general mnemonic is provided for the assignment of chirality.

Bulky melamine‐based Zn‐porphyrin tweezer as a CD probe of molecular chirality

“…Specifically, in an effort to enhance stereodifferentiation and hence provide more reliable AC assignment of bifunctional compounds (diamines, diols, amino-alcohols, and epoxyalcohols), Borhan and coworkers have designed bulkier analogs of tweezer A, which also form 1:1 complexes. 18,19 Inoue and coworkers have developed a dimer of octaethyl free base, Zn-or Mg-porphyrin linked by a short ethane bridge 20 as well as its chlorin analog. 21,22 The latter dimeric porphyrin hosts with closely attached porphyrins predominantly coordinate monodentate guests such as amines and alcohols, forming 1:2 host/guest complexes with moderately intense CD signals.…”

Porphyrin tweezer receptors: Binding studies, conformational properties and applications

“…These include the use of different metals at the porphyrin core (Zn (II) and Mg(II)) [27], changes in the length of the spacer (n = 1, 3) [28], and the decoration of the meso-position of the porphyrin ring with different phenyl substituents [29,30,31,32]. that for some substrates the carbonyl oxygen atom of an amide group could act as an alternative binding site to the nitrogen atom of one of the two primary amino groups.…”

“…In trying to overcome this limitation, Bohran et al synthesized tweezer receptors bearing electron-deficient porphyrin units(T3a -T3b, Figure 8). The aim of this work was to increase the association constants of complexes between dihydroxylated guest and tweezer receptors containing Zn-porphyrin units with a strong electropositive character[29,30,31]. already known that electron-deficient monoporphyrins decorated with polyfluorinated phenyl groups at their meso-positions (Figure 9) produce 1:1 complexes with monoamines and monoalcohols having association constants values that are one or two orders of magnitude higher than their non-fluorinated counterparts (i.e.…”

Palladium-Catalyzed Polyfluorophenylation of Porphyrins with Bis(polyfluorophenyl)zinc Reagents

“…The construction of porphyrins and related tetrapyrrolic macrocycles has attracted much interest [1][2][3][4][5][6] because they have a variety of important applications in many fields [7,8], including catalysis [9][10][11][12][13][14], medicine [15][16][17][18], and materials [19][20][21][22][23][24][25][26][27]. It is also well documented that the chemical, physical, and biological properties of porphyrin macrocycles can be systematically tuned by the electronic, steric and conformational environments of their peripheral substituents [7,8].…”

“…Penta-fluoro-phenyl and related polyfluorophenyl groups are one of the most important peripheral substituents in that their strong electron-withdrawing nature can greatly affect the electronic properties of a porphyrin core [25,27]. Conventional approaches to synthesizing pentafluorophenyl-substituted porphyrins involve multiple condensation reactions of pentafluorobenzaldehydes by using various monopyrroles or substituted dipyrromethanes under acidic conditions, followed by oxidation of the OPEN ACCESS resulting porphyrinogen intermediates [26][27][28][29][30]. However, these multiple-condensation methods have low yields, significant side products, and difficult purifications.…”