First synthesis of meso-substituted pyrrolo[1,2-a]quinoxalinoporphyrins

• Dileep Kumar Singh and
• Mahendra Nath

Beilstein J. Org. Chem. 2014, 10, 808–813, doi:10.3762/bjoc.10.76

• ]quinoxalinoporphyrins; Pictet–Spengler reaction; synthesis; Introduction Many natural porphyrins are known to play essential roles in a number of biological processes including oxygen transport [1], solar energy conservation [2][3][4] and photosynthesis [5]. Owing to the expanded π-conjugation system as well as good

• thermal stabilities, various artificial porphyrins have been prepared as promising materials for organic photonic and electronic applications [6][7][8][9]. In addition, porphyrins fused with external aromatic systems exhibit a broad range of applications in diverse areas such as molecular devices [10][11

• of biologically important functional groups were also introduced on the periphery of meso-substituted porphyrins to develop efficient photosensitizers for photodynamic therapy applications [41][42][43]. However, the porphyrins with a pyrrolo[1,2-a]quinoxaline moiety at the meso-positions have not

From porphyrin benzylphosphoramidate conjugates to the catalytic hydrogenation of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin

• Marcos C. de Souza,
• Leandro F. Pedrosa,
• Géssica S. Cazagrande,
• Vitor F. Ferreira,
• Maria G. P. M. S. Neves and
• José A. S. Cavaleiro

Beilstein J. Org. Chem. 2014, 10, 628–633, doi:10.3762/bjoc.10.54

• reduction of the macrocycle, thereby affording chlorin and other derivatives (Scheme 1). Considering the importance of TPPF20 as a template for further functionalizations [7] and the better suitability of chlorins for PDT compared to porphyrins due to their enhanced red-shifted Q bands [2], we decided to

• with 10% Pd/C and NEt3 the benzyl groups could not be selectively removed without affecting the phosphoramidate moiety and the porphyrin core. Catalytic hydrogenation of TPPF20 with H2/10% Pd/C There are many methods for performing the reduction of porphyrins (or metalloporphyrins) leading to different

• levels of hydrogenation on the β-pyrrolic double bonds [12][13]. Most of these methods employ chemicals other than H2 as hydrogen donors to reduce porphyrins into chlorins [14][15][16][17][18]. In our case, we decided to investigate the extent of the direct catalytic hydrogenation with H2 over TPPF20 in

Simple two-step synthesis of 2,4-disubstituted pyrroles and 3,5-disubstituted pyrrole-2-carbonitriles from enones

• Murat Kucukdisli,
• Dorota Ferenc,
• Marcel Heinz,
• Christine Wiebe and
• Till Opatz

Beilstein J. Org. Chem. 2014, 10, 466–470, doi:10.3762/bjoc.10.44

• connection to the porphyrins, the chlorins, and the corrins. Furthermore, they are regarded as privileged structures by synthetic chemists because of widespread applications in medicinal chemistry [2][3] and materials science [4]. Not surprisingly, numerous synthetic methods [5][6][7][8][9][10][11][12][13

Synthesis of meso-substituted dihydro-1,3-oxazinoporphyrins

• Satyasheel Sharma and
• Mahendra Nath

Beilstein J. Org. Chem. 2013, 9, 496–502, doi:10.3762/bjoc.9.53

• derived from porphyrins [11][12]. Previously, a large number of these molecules have been synthesized by the coupling of diverse pharmaceutically important moieties, such as carbohydrates [13][14][15], amino acid residues [16][17][18][19], steroids [20][21], glycosides [22][23][24], nitroxyl derivatives

• . Further, these free-base porphyrins were successfully converted to their zinc(II) analogues 10–13 by using Zn(OAc)2·2H2O as outlined in Scheme 1. In contrast, the synthesis of new dihydro-1,3-naphthoxazinoporphyrins 14 and 16 was achieved in 75–85% yields in a one-pot three-component Mannich type

• -dihydroxynaphthalenes and formaldehyde in THF under reflux (Scheme 3). Attempts have also been made to prepare the corresponding zinc naphthoxazinoporphyrin dyads, but always impure products were obtained even after repeated column chromatography. The newly synthesized porphyrins were characterized on the basis of 1H

Intramolecular carbenoid ylide forming reactions of 2-diazo-3-keto-4-phthalimidocarboxylic esters derived from methionine and cysteine

• Marc Enßle,
• Stefan Buck,
• Roland Werz and
• Gerhard Maas

Beilstein J. Org. Chem. 2012, 8, 433–440, doi:10.3762/bjoc.8.49

• sulfonium ylide 20 in practically quantitative yield. It has recently been reported that ruthenium(II) porphyrins are suitable catalysts for carbenoid sulfonium ylide formation as well [43]. In continuation of our comparative studies of dirhodium(II,II) tetracarboxylate and tetracarbonyldiruthenium(I,I

Fifty years of oxacalix[3]arenes: A review

• Kevin Cottet,
• Paula M. Marcos and
• Peter J. Cragg

Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22

• incorporate porphyrin linkers between two oxacalix[3]arenes, but, due to the size of the porphyrins and their rigidity, only the capsular form was found [50]. Treatment with zinc(II) acetate introduced three equivalents of the metal, one for each porphyrin unit. 3.2.3 Capping the upper rim: Capping the upper

Ene–yne cross-metathesis with ruthenium carbene catalysts

• Cédric Fischmeister and
• Christian Bruneau

Beilstein J. Org. Chem. 2011, 7, 156–166, doi:10.3762/bjoc.7.22

• the disubstituted double bond possessing a (Z)-configuration does not participate in Diels–Alder reactions [61]. Using the EYCM/Diels–Alder sequence, tetrahydropyridines [57], substituted phenylalanines [71][72], modified porphyrins [73], carbocycle-linked oligosaccharides [74] and heterocycles [75

Self-assembly and semiconductivity of an oligothiophene supergelator

• Pampa Pratihar,
• Suhrit Ghosh,
• Vladimir Stepanenko,
• Sameer Patwardhan,
• Ferdinand C. Grozema,
• Laurens D. A. Siebbeles and
• Frank Würthner

Beilstein J. Org. Chem. 2010, 6, 1070–1078, doi:10.3762/bjoc.6.122

• these elongated fibres form interpenetrating network in which the solvent molecules are trapped [3][4]. Organogels based on various π-systems such as oligophenylenevinylenes [5] and thienylenevinylenes [6] oligophenyleneethylenes [7], phthalocyanines [8], porphyrins [9], naphthalene and perylene

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

• enclosed on all sides by the receptor being “trapped” as in a cage forming clathrates [35]. Binding of the amino group to a planar surface of the receptor is found in metal complexes or metalla-porphyrins. The molecular environment and the solvent determine the stability of the assembly: competitive

• ]. Many types of synthetic ammonium ion receptors are available, ranging from crown ethers, calixarenes, porphyrins, cucurbiturils, cyclodextrins and cyclopeptides to tweezer ligands, sterically geared tripods and several types of metal complexes. The most important methods used for evaluating ammonium

• substance classes that have been mostly used in organic ammonium ion recognition: crown ethers, calixarenes [54], cyclodextrins [55][56][57], cucurbiturils, porphyrins, phosphonate based receptors, tripodal receptors, tweezer ligands, clefts, cyclopeptides and metal complexes. We have not included rotaxanes

Versatile supramolecular reactivity of zinc-tetra(4-pyridyl)porphyrin in crystalline solids: Polymeric grids with zinc dichloride and hydrogen-bonded networks with mellitic acid

• Sophia Lipstman and
• Israel Goldberg

Beilstein J. Org. Chem. 2009, 5, No. 77, doi:10.3762/bjoc.5.77

• Å). It is further coordinated to two additional porphyrins with the aid of the tetrahedral zinc dichloride connectors (at Zn–N = 2.040 and 2.046 Å), each bridging between pyridyl groups of two neighboring moieties. The fourth pyridyl group is not involved in intermolecular coordination, and is

• rotationally disordered in the crystal. Such a four-point per porphyrin binding model, which involves the zinc ion and three of the pyridyl groups, results in the formation of a 2D grid coordination polymer wherein neighboring porphyrins are roughly perpendicular to each other. There is a considerable

• hydrogen bonded to four adjacent acids, and every acid is hydrogen bonded to four different porphyrins. This connectivity scheme results in a fascinating supramolecular grid sustained by such cooperative COOH···Npy hydrogen bonding (at N···O within 2.56–2.62 Å). The layered array thus formed has an open

One-pot preparation of substituted pyrroles from α-diazocarbonyl compounds

• Fernando de C. da Silva,
• Mauricio G. Fonseca,
• Renata de S. Rianelli,
• Anna C. Cunha,
• Maria C. B. V. de Souza and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2008, 4, No. 45, doi:10.3762/bjoc.4.45

• -indolyl alkanols that are important for the synthesis of porphyrins, using montmorillonite KSF as catalyst. The search for short procedures for the synthesis of highly functionalized pyrrole derivatives is still desirable [25][26][27]. In the next years the organic synthetic chemists will have more