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Condensation

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Condensation - Free Register to Access Experts & Abstracts

Wolfram Sirges - One of the best experts on this subject based on the ideXlab platform.

  • novel porphyrinoids 14 biomimetic syntheses of doubly n n bridged 18 porphyrinogens
    European Journal of Organic Chemistry, 1993
    Co-Authors: Burchard Franck, Ralf Timmermann, Wolfram Sirges
    Abstract:

    Six N,N′-alkylene-bridged bispyrroles 9a–9e and one N,N′-oxaalkylene-bridged bispyrrole 16 with a reactive group at C-1 of each pyrrole unit were synthesized in 53–78% yields. Acid-catalyzed “biomimetic” Condensations of the bispyrroles with N,N′-C3 to N,N′-C5 bridges yielded N,N′:N″,N‴doubly bridged porphyrinogens 14, 15, 17, 18, which are novel heterocyclic systems. By exchanging one CH2 group for oxygen in the N,N′-alkylene chain of 9e to reduce the Prelog strain, the Condensation yield was significantly increased. The N,N′-C1-and the N,N′-C2-bridged bispyrroles 9a, 9b did not cyclize to porphyrinogens, but in one case cyclized to give a N,N′-C1-bridged dipyrrylmethane 12 instead.

  • Novel Porphyrinoids, 14. – Biomimetic Syntheses of Doubly N,N′‐Bridged [18]Porphyrinogens
    European Journal of Organic Chemistry, 1993
    Co-Authors: Burchard Franck, Ralf Timmermann, Wolfram Sirges
    Abstract:

    Six N,N′-alkylene-bridged bispyrroles 9a–9e and one N,N′-oxaalkylene-bridged bispyrrole 16 with a reactive group at C-1 of each pyrrole unit were synthesized in 53–78% yields. Acid-catalyzed “biomimetic” Condensations of the bispyrroles with N,N′-C3 to N,N′-C5 bridges yielded N,N′:N″,N‴doubly bridged porphyrinogens 14, 15, 17, 18, which are novel heterocyclic systems. By exchanging one CH2 group for oxygen in the N,N′-alkylene chain of 9e to reduce the Prelog strain, the Condensation yield was significantly increased. The N,N′-C1-and the N,N′-C2-bridged bispyrroles 9a, 9b did not cyclize to porphyrinogens, but in one case cyclized to give a N,N′-C1-bridged dipyrrylmethane 12 instead.

Sarasij K Upadhyay - One of the best experts on this subject based on the ideXlab platform.

Fabrizio Machetti - One of the best experts on this subject based on the ideXlab platform.

  • conjugate addition versus cycloaddition Condensation of nitro compounds in water selectivity acid base catalysis and induction period
    Chemistry: A European Journal, 2013
    Co-Authors: Luca Guideri, Francesco De Sarlo, Fabrizio Machetti
    Abstract:

    : Nitroacetates and nitroacetamides react in water as in chloroform with electron-deficient dipolarophiles to give Condensation or conjugate addition products under base catalysis. In general, high selectivity towards Condensation is observed in water, with shorter induction periods than in chloroform. In water, Condensations slowly occur even without base; kinetic profiles evidence the catalytic effect of the base, which should be related to the conversion into the tautomer nitronic acid. Condensations in water provide convenient access to isoxazole derivatives bearing various functional groups including ammonium, carboxy, and carboxyamide.

  • Conjugate addition versus cycloaddition/Condensation of nitro compounds in water: selectivity, acid-base catalysis, and induction period.
    Chemistry: A European Journal, 2012
    Co-Authors: Luca Guideri, Francesco De Sarlo, Fabrizio Machetti
    Abstract:

    : Nitroacetates and nitroacetamides react in water as in chloroform with electron-deficient dipolarophiles to give Condensation or conjugate addition products under base catalysis. In general, high selectivity towards Condensation is observed in water, with shorter induction periods than in chloroform. In water, Condensations slowly occur even without base; kinetic profiles evidence the catalytic effect of the base, which should be related to the conversion into the tautomer nitronic acid. Condensations in water provide convenient access to isoxazole derivatives bearing various functional groups including ammonium, carboxy, and carboxyamide.

Burchard Franck - One of the best experts on this subject based on the ideXlab platform.

  • novel porphyrinoids 14 biomimetic syntheses of doubly n n bridged 18 porphyrinogens
    European Journal of Organic Chemistry, 1993
    Co-Authors: Burchard Franck, Ralf Timmermann, Wolfram Sirges
    Abstract:

    Six N,N′-alkylene-bridged bispyrroles 9a–9e and one N,N′-oxaalkylene-bridged bispyrrole 16 with a reactive group at C-1 of each pyrrole unit were synthesized in 53–78% yields. Acid-catalyzed “biomimetic” Condensations of the bispyrroles with N,N′-C3 to N,N′-C5 bridges yielded N,N′:N″,N‴doubly bridged porphyrinogens 14, 15, 17, 18, which are novel heterocyclic systems. By exchanging one CH2 group for oxygen in the N,N′-alkylene chain of 9e to reduce the Prelog strain, the Condensation yield was significantly increased. The N,N′-C1-and the N,N′-C2-bridged bispyrroles 9a, 9b did not cyclize to porphyrinogens, but in one case cyclized to give a N,N′-C1-bridged dipyrrylmethane 12 instead.

  • Novel Porphyrinoids, 14. – Biomimetic Syntheses of Doubly N,N′‐Bridged [18]Porphyrinogens
    European Journal of Organic Chemistry, 1993
    Co-Authors: Burchard Franck, Ralf Timmermann, Wolfram Sirges
    Abstract:

    Six N,N′-alkylene-bridged bispyrroles 9a–9e and one N,N′-oxaalkylene-bridged bispyrrole 16 with a reactive group at C-1 of each pyrrole unit were synthesized in 53–78% yields. Acid-catalyzed “biomimetic” Condensations of the bispyrroles with N,N′-C3 to N,N′-C5 bridges yielded N,N′:N″,N‴doubly bridged porphyrinogens 14, 15, 17, 18, which are novel heterocyclic systems. By exchanging one CH2 group for oxygen in the N,N′-alkylene chain of 9e to reduce the Prelog strain, the Condensation yield was significantly increased. The N,N′-C1-and the N,N′-C2-bridged bispyrroles 9a, 9b did not cyclize to porphyrinogens, but in one case cyclized to give a N,N′-C1-bridged dipyrrylmethane 12 instead.

Faiz Ahmed Khan - One of the best experts on this subject based on the ideXlab platform.