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Hans-joachim Knölker - One of the best experts on this subject based on the ideXlab platform.
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First Total Synthesis of the Cytotoxic Carbazole Alkaloid Excavatine‐A and Regioselective Annulation to Pyrano[2,3‐a]Carbazoles and [1,4]Oxazepino[2,3,4‐jk]Carbazoles
European Journal of Organic Chemistry, 2017Co-Authors: Christian Brütting, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:We describe the first total synthesis of the cytotoxic carbazole alkaloid excavatine-A (1). The carbazole framework was constructed via double C-H bond activation of a diarylamine using our palladium(II)-catalyzed oxidative cyclization. Treatment of the intermediate 8-hydroxyCarbazoles 8 with prenal (7) and different additives led either to the pyrano[2,3-a]Carbazoles 6 or the [1,4]oxazepino[2,3,4-jk]Carbazoles 15. The pyran annulation was investigated to determine the influence of substitution pattern, additives, and reaction time on the selectivity.
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synthesis of prenyl and geranyl substituted carbazole alkaloids by dibal h promoted reductive pyran ring opening of dialkylpyrano 3 2 a Carbazoles
Chemistry: A European Journal, 2014Co-Authors: Ronny Hesse, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:The DIBAL-H promoted reductive pyran ring opening of dialkylpyrano[3,2-a]Carbazoles provides a direct access to a broad range of prenyl- and geranyl-substituted Carbazoles. Formation of a pyran ring followed by reductive ring opening represents a new method for the introduction of prenyl and geranyl groups. In the course of the present work, we achieved the first total syntheses of the following eight carbazole alkaloids: clauraila-E, 7-hydroxyheptaphylline, 7-methoxyheptaphylline, mukoenine-B (clausenatine-A), mukoenine-A (girinimbilol), mahanimbinol (mahanimbilol), euchrestine-A, and isomurrayafoline-B.
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Synthesis of Prenyl‐ and Geranyl‐Substituted Carbazole Alkaloids by DIBAL‐H Promoted Reductive Pyran Ring Opening of Dialkylpyrano[3,2‐a]Carbazoles
Chemistry: A European Journal, 2014Co-Authors: Ronny Hesse, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:The DIBAL-H promoted reductive pyran ring opening of dialkylpyrano[3,2-a]Carbazoles provides a direct access to a broad range of prenyl- and geranyl-substituted Carbazoles. Formation of a pyran ring followed by reductive ring opening represents a new method for the introduction of prenyl and geranyl groups. In the course of the present work, we achieved the first total syntheses of the following eight carbazole alkaloids: clauraila-E, 7-hydroxyheptaphylline, 7-methoxyheptaphylline, mukoenine-B (clausenatine-A), mukoenine-A (girinimbilol), mahanimbinol (mahanimbilol), euchrestine-A, and isomurrayafoline-B.
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Synthesis of Pyrrole and Carbazole Alkaloids
Topics in current chemistry, 2011Co-Authors: Ingmar Bauer, Hans-joachim KnölkerAbstract:An overview of recent transition metal-catalyzed syntheses of pyrroles and Carbazoles is presented. The focus is on methods which have been applied to the preparation of biologically active naturally occurring pyrrole and carbazole alkaloids. For pyrroles, special attention is paid to silver(I)-catalyzed cyclization reactions. For Carbazoles, iron(0)-mediated and palladium(0/II)-catalyzed cyclization reactions are highlighted and their broad range of applications is discussed.
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Chemistry of Carbazole Alkaloids
The Alkaloids: Chemistry and Biology, 2008Co-Authors: Hans-joachim Knölker, Kethiri R. ReddyAbstract:Publisher Summary The chapter presents a discussion on the chemistry of carbazole alkaloids and summarizes the different synthetic methods. The application of several procedures to the total synthesis of natural products is also discussed. The chapter discusses synthesis of Carbazoles by deoxygenation of nitrobiphenyls, synthesis of Carbazoles from azidobiphenyls, synthesis of Carbazoles by cyclization of 2,2’-diaminobiphenyls, synthesis of Carbazoles by cyclization of arylhydrazones, and so on. Cadogan developed a similar deoxygenative cyclization using refluxing triethylphosphite as solvent, and this method remained as the most common procedure for this conversion, which tolerates a variety of substituents on the o-nitrobiphenyls to afford diverse, functionalized carbazole derivatives. The widely accepted mechanism for this transformation involves exhaustive deoxygenation to a singlet nitrene that undergoes a downstream C–H insertion. The preparation of the hydrazone required in the Borsche method was accomplished very conveniently using the Japp–Klingemann reaction. The reaction uses formylcyclohexanone and a diazotized aromatic amine for the synthesis of hydrazone. This chapter also includes a discussion on the total synthesis of simple tricyclic Carbazoles and on the tricyclic Carbazoles substituted either at the C-ring or at the 9(N)-of the carbazole nucleus.
Arndt W. Schmidt - One of the best experts on this subject based on the ideXlab platform.
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First Total Synthesis of the Cytotoxic Carbazole Alkaloid Excavatine‐A and Regioselective Annulation to Pyrano[2,3‐a]Carbazoles and [1,4]Oxazepino[2,3,4‐jk]Carbazoles
European Journal of Organic Chemistry, 2017Co-Authors: Christian Brütting, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:We describe the first total synthesis of the cytotoxic carbazole alkaloid excavatine-A (1). The carbazole framework was constructed via double C-H bond activation of a diarylamine using our palladium(II)-catalyzed oxidative cyclization. Treatment of the intermediate 8-hydroxyCarbazoles 8 with prenal (7) and different additives led either to the pyrano[2,3-a]Carbazoles 6 or the [1,4]oxazepino[2,3,4-jk]Carbazoles 15. The pyran annulation was investigated to determine the influence of substitution pattern, additives, and reaction time on the selectivity.
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synthesis of prenyl and geranyl substituted carbazole alkaloids by dibal h promoted reductive pyran ring opening of dialkylpyrano 3 2 a Carbazoles
Chemistry: A European Journal, 2014Co-Authors: Ronny Hesse, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:The DIBAL-H promoted reductive pyran ring opening of dialkylpyrano[3,2-a]Carbazoles provides a direct access to a broad range of prenyl- and geranyl-substituted Carbazoles. Formation of a pyran ring followed by reductive ring opening represents a new method for the introduction of prenyl and geranyl groups. In the course of the present work, we achieved the first total syntheses of the following eight carbazole alkaloids: clauraila-E, 7-hydroxyheptaphylline, 7-methoxyheptaphylline, mukoenine-B (clausenatine-A), mukoenine-A (girinimbilol), mahanimbinol (mahanimbilol), euchrestine-A, and isomurrayafoline-B.
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Synthesis of Prenyl‐ and Geranyl‐Substituted Carbazole Alkaloids by DIBAL‐H Promoted Reductive Pyran Ring Opening of Dialkylpyrano[3,2‐a]Carbazoles
Chemistry: A European Journal, 2014Co-Authors: Ronny Hesse, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:The DIBAL-H promoted reductive pyran ring opening of dialkylpyrano[3,2-a]Carbazoles provides a direct access to a broad range of prenyl- and geranyl-substituted Carbazoles. Formation of a pyran ring followed by reductive ring opening represents a new method for the introduction of prenyl and geranyl groups. In the course of the present work, we achieved the first total syntheses of the following eight carbazole alkaloids: clauraila-E, 7-hydroxyheptaphylline, 7-methoxyheptaphylline, mukoenine-B (clausenatine-A), mukoenine-A (girinimbilol), mahanimbinol (mahanimbilol), euchrestine-A, and isomurrayafoline-B.
Olga Kataeva - One of the best experts on this subject based on the ideXlab platform.
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First Total Synthesis of the Cytotoxic Carbazole Alkaloid Excavatine‐A and Regioselective Annulation to Pyrano[2,3‐a]Carbazoles and [1,4]Oxazepino[2,3,4‐jk]Carbazoles
European Journal of Organic Chemistry, 2017Co-Authors: Christian Brütting, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:We describe the first total synthesis of the cytotoxic carbazole alkaloid excavatine-A (1). The carbazole framework was constructed via double C-H bond activation of a diarylamine using our palladium(II)-catalyzed oxidative cyclization. Treatment of the intermediate 8-hydroxyCarbazoles 8 with prenal (7) and different additives led either to the pyrano[2,3-a]Carbazoles 6 or the [1,4]oxazepino[2,3,4-jk]Carbazoles 15. The pyran annulation was investigated to determine the influence of substitution pattern, additives, and reaction time on the selectivity.
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synthesis of prenyl and geranyl substituted carbazole alkaloids by dibal h promoted reductive pyran ring opening of dialkylpyrano 3 2 a Carbazoles
Chemistry: A European Journal, 2014Co-Authors: Ronny Hesse, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:The DIBAL-H promoted reductive pyran ring opening of dialkylpyrano[3,2-a]Carbazoles provides a direct access to a broad range of prenyl- and geranyl-substituted Carbazoles. Formation of a pyran ring followed by reductive ring opening represents a new method for the introduction of prenyl and geranyl groups. In the course of the present work, we achieved the first total syntheses of the following eight carbazole alkaloids: clauraila-E, 7-hydroxyheptaphylline, 7-methoxyheptaphylline, mukoenine-B (clausenatine-A), mukoenine-A (girinimbilol), mahanimbinol (mahanimbilol), euchrestine-A, and isomurrayafoline-B.
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Synthesis of Prenyl‐ and Geranyl‐Substituted Carbazole Alkaloids by DIBAL‐H Promoted Reductive Pyran Ring Opening of Dialkylpyrano[3,2‐a]Carbazoles
Chemistry: A European Journal, 2014Co-Authors: Ronny Hesse, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:The DIBAL-H promoted reductive pyran ring opening of dialkylpyrano[3,2-a]Carbazoles provides a direct access to a broad range of prenyl- and geranyl-substituted Carbazoles. Formation of a pyran ring followed by reductive ring opening represents a new method for the introduction of prenyl and geranyl groups. In the course of the present work, we achieved the first total syntheses of the following eight carbazole alkaloids: clauraila-E, 7-hydroxyheptaphylline, 7-methoxyheptaphylline, mukoenine-B (clausenatine-A), mukoenine-A (girinimbilol), mahanimbinol (mahanimbilol), euchrestine-A, and isomurrayafoline-B.
Ronny Hesse - One of the best experts on this subject based on the ideXlab platform.
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synthesis of prenyl and geranyl substituted carbazole alkaloids by dibal h promoted reductive pyran ring opening of dialkylpyrano 3 2 a Carbazoles
Chemistry: A European Journal, 2014Co-Authors: Ronny Hesse, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:The DIBAL-H promoted reductive pyran ring opening of dialkylpyrano[3,2-a]Carbazoles provides a direct access to a broad range of prenyl- and geranyl-substituted Carbazoles. Formation of a pyran ring followed by reductive ring opening represents a new method for the introduction of prenyl and geranyl groups. In the course of the present work, we achieved the first total syntheses of the following eight carbazole alkaloids: clauraila-E, 7-hydroxyheptaphylline, 7-methoxyheptaphylline, mukoenine-B (clausenatine-A), mukoenine-A (girinimbilol), mahanimbinol (mahanimbilol), euchrestine-A, and isomurrayafoline-B.
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Synthesis of Prenyl‐ and Geranyl‐Substituted Carbazole Alkaloids by DIBAL‐H Promoted Reductive Pyran Ring Opening of Dialkylpyrano[3,2‐a]Carbazoles
Chemistry: A European Journal, 2014Co-Authors: Ronny Hesse, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:The DIBAL-H promoted reductive pyran ring opening of dialkylpyrano[3,2-a]Carbazoles provides a direct access to a broad range of prenyl- and geranyl-substituted Carbazoles. Formation of a pyran ring followed by reductive ring opening represents a new method for the introduction of prenyl and geranyl groups. In the course of the present work, we achieved the first total syntheses of the following eight carbazole alkaloids: clauraila-E, 7-hydroxyheptaphylline, 7-methoxyheptaphylline, mukoenine-B (clausenatine-A), mukoenine-A (girinimbilol), mahanimbinol (mahanimbilol), euchrestine-A, and isomurrayafoline-B.
Bin Wang - One of the best experts on this subject based on the ideXlab platform.
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n bromosuccinimide nbs catalyzed c h bond functionalization an annulation of alkynes with electron withdrawing group ewg substituted acetyl indoles for the synthesis of Carbazoles
Organic Letters, 2017Co-Authors: Han Wang, Zhen Wang, Yilong Wang, Ruirui Zhou, Siyao Yin, Xu Yan, Bin WangAbstract:An N-bromosuccinimide-catalyzed intermolecular annulation of acetyl indoles with alkynes was developed, allowing for regioselective formation of valuable Carbazoles through direct C–H bond functionalization. The readily available catalyst, wide substrate scope, gram scale synthesis, and mild conditions make this method practical. Mechanistic investigations indicate that the bromination of acetyl indole takes place to generate a bromide intermediate, followed by coupling with an alkyne and intramolecular cycloaromatization to furnish carbazole products.
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N‑Bromosuccinimide (NBS)-Catalyzed C–H Bond Functionalization: An Annulation of Alkynes with Electron Withdrawing Group (EWG)-Substituted Acetyl Indoles for the Synthesis of Carbazoles
2017Co-Authors: Han Wang, Zhen Wang, Yilong Wang, Ruirui Zhou, Siyao Yin, Xu Yan, Bin WangAbstract:An N-bromosuccinimide-catalyzed intermolecular annulation of acetyl indoles with alkynes was developed, allowing for regioselective formation of valuable Carbazoles through direct C–H bond functionalization. The readily available catalyst, wide substrate scope, gram scale synthesis, and mild conditions make this method practical. Mechanistic investigations indicate that the bromination of acetyl indole takes place to generate a bromide intermediate, followed by coupling with an alkyne and intramolecular cycloaromatization to furnish carbazole products