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Ikyon Kim - One of the best experts on this subject based on the ideXlab platform.
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Domino Knoevenagel Condensation/Intramolecular Aldol Cyclization Route to Diverse Indolizines with Densely Functionalized Pyridine Units
2016Co-Authors: Myungock Kim, Youngeun Jung, Ikyon KimAbstract:A highly efficient [4 + 2] annulation route to polysubstituted indolizines is described employing a domino Knoevenagel condensation/intramolecular aldol cyclization process as a key step. Construction of pyridine rings in indolizine skeleton was rapidly achieved from several Pyrrole-2-Carboxaldehydes in good to excellent yields, leading to indolizines with various substituents at the 5, 6, and 7 positions depending on the reacting active methylene partners
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domino knoevenagel condensation intramolecular aldol cyclization route to diverse indolizines with densely functionalized pyridine units
Journal of Organic Chemistry, 2013Co-Authors: Myungock Kim, Youngeun Jung, Ikyon KimAbstract:A highly efficient [4 + 2] annulation route to polysubstituted indolizines is described employing a domino Knoevenagel condensation/intramolecular aldol cyclization process as a key step. Construction of pyridine rings in indolizine skeleton was rapidly achieved from several Pyrrole-2-Carboxaldehydes in good to excellent yields, leading to indolizines with various substituents at the 5, 6, and 7 positions depending on the reacting active methylene partners.
Vanessa Desplat - One of the best experts on this subject based on the ideXlab platform.
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new ferrocenic pyrrolo 1 2 a quinoxaline derivatives synthesis and in vitro antimalarial activity part ii
European Journal of Medicinal Chemistry, 2011Co-Authors: Jean Guillon, Elisabeth Mouray, Stephane Moreau, Catherine Mullie, Isabelle Forfar, Vanessa DesplatAbstract:Following our search for antimalarial compounds, novel series of ferrocenyl-substituted pyrrolo[1,2-a]quinoxalines 1-2 were synthesized from ferrocene-carboxaldehyde and tested for their in vitro activity upon the erythrocytic development of Plasmodium falciparum strains with different chloroquine-resistance status. The ferrocenic pyrrolo[1,2-a]quinoxalines 1-2 were prepared in 6 or 9 steps through a Barton-Zard reaction. Promising pharmacological results against FcB1, K1 and F32 strains were obtained with ferrocenyl pyrrolo[1,2-a]quinoxalines 1j-l linked by a bis-(3-aminopropyl)piperazine linker substituted by a nitrobenzyl moiety.
Jonathan S Lindsey - One of the best experts on this subject based on the ideXlab platform.
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construction of the bacteriochlorin macrocycle with concomitant nazarov cyclization to form the annulated isocyclic ring analogues of bacteriochlorophyll a
Journal of Organic Chemistry, 2017Co-Authors: Shaofei Zhang, Jonathan S LindseyAbstract:Bacteriochlorophylls contain a bacteriochlorin macrocycle bearing an annulated fifth ring. The fifth ring, termed the isocyclic ring or ring E, is equipped with 131-oxo and 132-carbomethoxy substituents. Herein, a general route to stable, synthetic bacteriochlorophyll analogues is described. Knoevenagel condensation (∼40 mM, rt, CH2Cl2, piperidine/AcOH/molecular sieves) of a dihydrodipyrrin–carboxaldehyde (AD half) and a dihydrodipyrrin substituted with a β-ketoester (BC half) forms a propenone bearing the two halves (a hydrobilin analogue). Subsequent treatment (0.2 mM) with acid (Yb(OTf)3, CH3CN, 80 °C) promotes a double ring-closure process: (i) condensation between the α-position of pyrrole ring A and the α-acetal unit attached to pyrroline ring B forms the bacteriochlorin macrocycle, and (ii) Nazarov cyclization of the β-(propenoyl)-substituted ring C forms the isocyclic ring (E). Five new bacteriochlorins bearing various substituents (alkyl/alkyl, aryl, and alkyl/ester) at positions 2 and 3 (β-pyrro...
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Construction of the Bacteriochlorin Macrocycle with Concomitant Nazarov Cyclization To Form the Annulated Isocyclic Ring: Analogues of Bacteriochlorophyll a
2017Co-Authors: Shaofei Zhang, Jonathan S LindseyAbstract:Bacteriochlorophylls contain a bacteriochlorin macrocycle bearing an annulated fifth ring. The fifth ring, termed the isocyclic ring or ring E, is equipped with 131-oxo and 132-carbomethoxy substituents. Herein, a general route to stable, synthetic bacteriochlorophyll analogues is described. Knoevenagel condensation (∼40 mM, rt, CH2Cl2, piperidine/AcOH/molecular sieves) of a dihydrodipyrrin–carboxaldehyde (AD half) and a dihydrodipyrrin substituted with a β-ketoester (BC half) forms a propenone bearing the two halves (a hydrobilin analogue). Subsequent treatment (0.2 mM) with acid (Yb(OTf)3, CH3CN, 80 °C) promotes a double ring-closure process: (i) condensation between the α-position of pyrrole ring A and the α-acetal unit attached to pyrroline ring B forms the bacteriochlorin macrocycle, and (ii) Nazarov cyclization of the β-(propenoyl)-substituted ring C forms the isocyclic ring (E). Five new bacteriochlorins bearing various substituents (alkyl/alkyl, aryl, and alkyl/ester) at positions 2 and 3 (β-pyrrole sites, ring A) and 132 carboalkoxy groups (R = Me or Et) were constructed in 37–61% yield from the hydrobilin analogues. The BC half and AD half are available in five and eight steps, respectively, from the corresponding Pyrrole-2-Carboxaldehyde and unsaturated ketone. The bacteriochlorins exhibit absorption spectra typical of bacteriopheophytins (free base bacteriochlorophylls), with a strong near-infrared absorption band (707–751 nm)
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refined syntheses of hydrodipyrrin precursors to chlorin and bacteriochlorin building blocks
Journal of Porphyrins and Phthalocyanines, 2009Co-Authors: Michael Krayer, Masahiko Taniguchi, Thiagarajan Balasubramanian, Marcin Ptaszek, Christian Ruzie, David L Cramer, Jonathan S LindseyAbstract:Bromo-substituted hydrodipyrrins are valuable precursors to synthetic bromo-chlorins and bromo-bacteriochlorins, which in turn are versatile substrates for derivatization in pursuit of diverse molecular designs. 8-bromo-2,3-dihydro-1-(1,1-dimethoxymethyl)-3,3-dimethyldipyrrin (1) is a crucial precursor in the rational synthesis of the bacteriochlorin building block 3,13-dibromo-8,8,18,18-tetramethylbacteriochlorin (H2BC-Br3Br13). 8-bromo-2,3,4,5-tetrahydro-1,3,3-trimethyldipyrrin (2) is a crucial precursor in the rational synthesis of the analogous 3,13-disubstituted chlorin building block (e.g.H2C-Br3M10Br13). The routes to 1 and 2 share a common precursor, namely 4-bromo-2-(2-nitroethyl)-1-N-tosylpyrrole (6-Ts), which is derived from Pyrrole-2-Carboxaldehyde. The prior seven-step synthesis of 1 from Pyrrole-2-Carboxaldehyde has limited access to H2BC-Br3Br13 given the large excesses of materials, extensive reliance on column chromatography, and low overall yield (1.4%). Refined procedures for synthesis of the common precursor 6-Ts as well as 1 and 2 afford the advantages of (1) diminished consumption of solvents and reagents, (2) limited or no use of chlorinated solvents, (3) limited or no chromatography, and (4) improved yields of most steps. Streamlined procedures enable the final two or three transformations to be performed without purification of intermediates. The new procedures facilitate the expedient preparation of 1 and 2 at the multigram scale.
Anil Kumar - One of the best experts on this subject based on the ideXlab platform.
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electronic epr and magnetic studies of co ii ni ii and cu ii complexes with thiosemicarbazone l1 and semicarbazone l2 derived from pyrole 2 carboxyaldehyde
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2007Co-Authors: Sulekh Chandra, Anil KumarAbstract:Abstract Co(II), Ni(II) and Cu(II) complexes are synthesized with thiosemicarbazone (L 1 ) and semicarbazone (L 2 ) derived from pyrole-2-carboxyaldehyde. These complexes are characterized by elemental analysis, molar conductance, magnetic susceptibility measurements, mass, IR, electronic and EPR spectral studies .The molar conductance measurements of the complexes in DMSO correspond to non-electrolytic nature except Co(L 1 ) 2 (NO 3 ) 2 and Ni(L 1 ) 2 (NO 3 ) 2 complexes which are 1:2 electrolytes. All the complexes are of high-spin type. On the basis of spectral studies an octahedral geometry may be assigned for Co(II) and Ni(II) complexes except Co(L 1 ) 2 (NO 3 ) 2 and Ni(L 1 ) 2 (NO 3 ) 2 which are of tetrahedral geometry. A tetragonal geometry may be suggested for Cu(II) complexes.
Myungock Kim - One of the best experts on this subject based on the ideXlab platform.
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Domino Knoevenagel Condensation/Intramolecular Aldol Cyclization Route to Diverse Indolizines with Densely Functionalized Pyridine Units
2016Co-Authors: Myungock Kim, Youngeun Jung, Ikyon KimAbstract:A highly efficient [4 + 2] annulation route to polysubstituted indolizines is described employing a domino Knoevenagel condensation/intramolecular aldol cyclization process as a key step. Construction of pyridine rings in indolizine skeleton was rapidly achieved from several Pyrrole-2-Carboxaldehydes in good to excellent yields, leading to indolizines with various substituents at the 5, 6, and 7 positions depending on the reacting active methylene partners
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domino knoevenagel condensation intramolecular aldol cyclization route to diverse indolizines with densely functionalized pyridine units
Journal of Organic Chemistry, 2013Co-Authors: Myungock Kim, Youngeun Jung, Ikyon KimAbstract:A highly efficient [4 + 2] annulation route to polysubstituted indolizines is described employing a domino Knoevenagel condensation/intramolecular aldol cyclization process as a key step. Construction of pyridine rings in indolizine skeleton was rapidly achieved from several Pyrrole-2-Carboxaldehydes in good to excellent yields, leading to indolizines with various substituents at the 5, 6, and 7 positions depending on the reacting active methylene partners.
