The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
Wolfram Sirges - One of the best experts on this subject based on the ideXlab platform.
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novel porphyrinoids 14 biomimetic syntheses of doubly n n bridged 18 porphyrinogens
European Journal of Organic Chemistry, 1993Co-Authors: Burchard Franck, Ralf Timmermann, Wolfram SirgesAbstract: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.
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Novel Porphyrinoids, 14. – Biomimetic Syntheses of Doubly N,N′‐Bridged [18]Porphyrinogens
European Journal of Organic Chemistry, 1993Co-Authors: Burchard Franck, Ralf Timmermann, Wolfram SirgesAbstract: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.
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hydrotalcite catalysis in ionic liquid medium a recyclable reaction system for heterogeneous knoevenagel and nitroaldol Condensation
Tetrahedron Letters, 2004Co-Authors: Faiz Ahmed Khan, Jyotirmayee Dash, Rashmirekha Satapathy, Sarasij K UpadhyayAbstract:Knoevenagel Condensation proceeds efficiently in recyclable [bmim]PF 6 and [bmim]BF 4 without any catalyst, and hydrotalcites in ionic liquid serve as a safe and recyclable reaction system for both Knoevenagel as well as nitroaldol Condensations.
Fabrizio Machetti - One of the best experts on this subject based on the ideXlab platform.
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conjugate addition versus cycloaddition Condensation of nitro compounds in water selectivity acid base catalysis and induction period
Chemistry: A European Journal, 2013Co-Authors: Luca Guideri, Francesco De Sarlo, Fabrizio MachettiAbstract:: 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.
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Conjugate addition versus cycloaddition/Condensation of nitro compounds in water: selectivity, acid-base catalysis, and induction period.
Chemistry: A European Journal, 2012Co-Authors: Luca Guideri, Francesco De Sarlo, Fabrizio MachettiAbstract:: 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.
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novel porphyrinoids 14 biomimetic syntheses of doubly n n bridged 18 porphyrinogens
European Journal of Organic Chemistry, 1993Co-Authors: Burchard Franck, Ralf Timmermann, Wolfram SirgesAbstract: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.
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Novel Porphyrinoids, 14. – Biomimetic Syntheses of Doubly N,N′‐Bridged [18]Porphyrinogens
European Journal of Organic Chemistry, 1993Co-Authors: Burchard Franck, Ralf Timmermann, Wolfram SirgesAbstract: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.
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hydrotalcite catalysis in ionic liquid medium a recyclable reaction system for heterogeneous knoevenagel and nitroaldol Condensation
Tetrahedron Letters, 2004Co-Authors: Faiz Ahmed Khan, Jyotirmayee Dash, Rashmirekha Satapathy, Sarasij K UpadhyayAbstract:Knoevenagel Condensation proceeds efficiently in recyclable [bmim]PF 6 and [bmim]BF 4 without any catalyst, and hydrotalcites in ionic liquid serve as a safe and recyclable reaction system for both Knoevenagel as well as nitroaldol Condensations.
