Pyrroles deuteration

Dioxacorroles are 18-7r-electron aromatic systems like corroles. They exhibit basicity intermediate between that of porphyrin and corrole, and require 1 h at 100 °C in TFA for complete deuteration of the meso positions. The furan protons are also substituted by deuterium under the same conditions after lOOh. Friedel-Crafts acylation occurs at C-5 while alkyl halides attack on the pyrrolic nitrogens to give a mixture of mono- and di-alkyl derivatives. 

IR and Raman Spectba of Pyrrole and Deuterated Derivatives in Liquid Phase ... 

The H-NMR spectra (Table I) show no evidence of tautomerism of 1-hydroxypyrroles to 2H- or 3//-pyrrole 1-oxides and are similar to those of corresponding pyrroles. The hydroxyl proton is not always seen, as in the case of 1-hydroxyindole, and is easily exchanged out by deuterium oxide. The H-NMR spectrum of 2-cyano-2-methyl-2//-pyrrole 1-oxide (2) in dimethyl sulfoxide (DMSO) was unambiguous (Table I), but in deuter-iochloroform, the 3- and 4-protons appeared at the same position. 

Evidence for the formation of carbanions from ketoximes and DMSO in the presence of large amounts of KOH is provided by partial deuterium exchange between DMSO-D6 and the a-position of ketoximes (75MI2 76S281) in the synthesis of pyrroles, along with partial deuteration of hydroxyl. 

The extended cyclic enolate derived from a simple pyrrol-3-en-2-one (butenolac-tam) has been deuterated at the 5-position with very high diastereoselectivity if the (g) nitrogen atom carries a a-methyl-p-methoxybenzyl group (de > 99 l).27 A similar diastereoselective protonation has been observed in a pyrrol-3-en-2-one formed by dearomatizing cyclization of a pyrrole. 

The preparation of the iron porphyrin TPPFeCl-d20 (21), where the phenyl groups are completely deuterated, has allowed the further characterization of the bis-cyano Fe(II) and Fe(III) porphyrins. In the spectrum of TPPFeIII(CN)21" in DMSO, the resonance at +15.45 ppm upfield from TMS is verified as the pyrrole H. Comparing the spectrum of TPPFe11 (CN),2 and TPPFe11 (CN)22--d20 shows the peak at -7.82 ppm from TMS to be the pyrrole H, and integration indicates that the... 

Figure 9. Trace A The 2H NMR spectrum from a solution of (N-MeTTP)FeuCl in CD2Cl2/CD3OD (4 1, vol/vol) at -90 °C. Trace B The NMR spectrum from the same solution after the addition of five equivalents of NaOCD3 at —90 °C. Trace B The 2H NMR spectrum from a similar solution as that in trace B prepared from the deuterated complex (N-CD3 d8-TTP)FenCl. Trace C The 1H NMR spectrum of a solution of (N-MeTTP)FeIICl and five equivalents of sodium p-cresolate at—60°C in toluene-d8/methanol-d4 (9 1, vol/vol). Trace C The upfield region of trace C. Resonance assignments Me, the N-methyl protons pyrr, the pyrrole protons o, the ortho protons of the p-tolyl substituents L0, Lm, Lp, the ortho, meta, and para resonances of the axial cresolato ligand. (Reproduced from reference 46. Copyright 1992 American Chemical Society.)...

Figure 12. Trace A 1H NMR spectrum of the porphyrin x-radical generated from (N -MeTTP)FenCl and excess m-CPBA (denoted 5 in this figure) at —90 °C in CD2Cl2. Trace B 2H NMR spectrum of 5 selectively deuterated at the meso-phenyl positions. Trace C 2H NMR spectrum of 5 selectively deuterated at the /3-pyrrole positions. (Reproduced with permission from reference 52. Copyright 1990.)...

Recently, evidence for the transient ex istence of cation-radicals from simple pyrroles and indoles has been furnished by the observation of anodic regiospecific cyanation of these heterocycles.455 Both heterocycles are preferentially cyanated at the 2-position. Methyl side chains at these positions are also activated to cyanation and deuteration. Indole cation-radicals have been generated by photoionization in an aqueous medium.456 Unsubstituted at N, their lifetime in neutral solution is 10-6sec before they lose the N-proton however, it is longer in more acidic conditions.456 The photophysical properties of indole, its cation-radical, and neutral radical have been the subject of a recent theoretical analysis.457 On anodic oxidation of 2,3-diphenyl indole in acetonitrile, the initially formed cation-radicals dimerize to a product identified, primarily on the basis of 13C NMR, as 3-(5-indolyl)-indolenine (141).458... 

N—H.. X system. (X = C1-, Br, 0, N). NH stretching and out-ofplane bending frequencies can also be simply related, as shown in Fig. 9 b. The points (Table 4) correspond to frequencies of imidazole and triazole molecules in different environments, i. e., physical state and in complexes with various metal salts. The range of the vNH (3550—2700 cm-1) and yNH(515—940 cm-1) frequencies is smaller than that of the O—H.. 0 system, the N—H.. X hydrogen bonds being weaker. The dyNH frequency shift is less than half that of the drNH shift and the dy/yo relative shift for imidazole crystal amounts to 83%. As shown by deuteration studies of these molecules (26,131) the NH out-of-plane mode of imidazole and triazole does not appear to be mixed with other out-of-plane vibrations. Yet the yNH(j 2i) vibration of pyrrole is strongly... 

RR spectra of Cu(OEC) were first reported by Ozaki et al.. Figure 15 compares the polarized RR spectra of Cu(OEC) with those of Cu(OEP). The RR bands of Cu(OEC) in the 900-1700 cm region were assigned on the basis of frequency shifts upon 15,20-deuteration of meso-carbons and N substitution of pyrrolic nitrogens . Anderson et and Hanson et al. also reported the RR spectra of metallo-chlorin derivatives. Ozaki et al. extended the comparative study of Fe(OEP) and Fe(OEC) to the Fe-L stretching and ligand internal modes. Here the vibrational spectra of M(OEC) are explained on the basis of M(OEP) and then the difference in the Fe-L interaction between Fe(OEC) and Fe(OEP) will be discussed. 

Reactivity First and foremost, porphyrins are aromatic molecules. For example, they undergo some of the electrophilic substitution reactions characteristic of aromatic compounds—nitration, halogenation, sulphona-tion, formylation, acylation, and deuteration. Porph)nins differ from molecules such as benzene, in that there are two different sites on the macrocycle where electrophilic substitution can take place with different reactivities the meso-position and the pyrrole p-position. Which of these... 

Orza, J.M., R. Escribano, and R. Navarro (1985). Out of plane vibracional assignments and potential function of pyrrole and deuterated derivatives. J. Chem. Soc. Faraday Trans. 81, 653. 

The synthesis of functionalized calix[4]pyrroles able to accommodate ion pairs within their cavities was first approached by using crown ether-like polyether straps to link two of the four meso-csxhon atoms of the calix[4]pyrrole framework. The first of such ditopic systems, receptor 7, reported by Kim, Sessler, and coworkers, was designed to contain a the calix[4]arene crown-6-moiety for cesium cation recognition, while retaining a calix[4]pyrrole subunit for anion recognition (cf. Fig. 12.6) [22]. In the solid state, the individual ions within the CsF ion pair complex, which are bound to 7, are separated from one another by a single methanol molecule that was presumably captured during crystallization. Proton NMR spectroscopic analyses, carried out in deuterated methanol/chloroform (1 9 vA ),... 

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