Acid‐Free Synthesis of Carbazoles and Carbazolequinones by Intramolecular Pd‐Catalyzed, Microwave‐Assisted Oxidative Biaryl Coupling Reactions – Efficient Syntheses of Murrayafoline A, 2‐Methoxy‐3‐methylcarbazole, and Glycozolidine

• Published in: European Journal of Organic Chemistry Vol. 2009; no. 27; pp. 4614 - 4621
• Main Authors: Sridharan, Vellaisamy, Martín, M. Antonia, Menéndez, J. Carlos
• Format: Book Review Journal Article
• Language: English
• Published: Weinheim WILEY‐VCH Verlag 01.09.2009; Wiley; Wiley-VCH
• Subjects: Biaryl coupling; Chemistry; Chemistry, Organic; C–H activation; Exact sciences and technology; Heterocycles; Heterocyclic compounds; Heterocyclic compounds with only one n hetero atom and condensed derivatives; Natural products; Noncondensed benzenic compounds; Organic chemistry; Physical Sciences; Preparations and properties; Quinones; Science & Technology; Heterocycles; ORGANIC-SYNTHESIS; DIRECT ARYLATION; TRANSITION-METAL-COMPLEXES; HOST MATERIALS; MEDIATED SYNTHESIS; Biaryl coupling; LIGHT-EMITTING-DIODES; Quinones; C-H activation; Natural products; DIENE COMPLEXES; PALLADIUM-PROMOTED SYNTHESIS; 1ST TOTAL-SYNTHESIS; Intramolecular reaction; Catalytic reaction; Nitrogen heterocycle; Carbazole derivatives; Quinone; Microwave; Palladium complex; Natural compound; Oxidative coupling; Chemical coupling; Aromatic compound; Chemical synthesis; Acid medium; Hydrogen bond
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.200900537

A mild and efficient methodology for the synthesis of oxygenated carbazoles from diarylamines under non‐acidic conditions was developed, based on a palladium‐catalyzed, microwave‐assisted double C–H bond activation process. This new protocol was successfully applied to the synthesis of three naturally occurring carbazoles, namely murrayafoline A, 2‐methoxy‐3‐methylcarbazole, and glycozolidine. The scope of the reaction was also expanded to include the synthesis of benzo fused carbazolequinones.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) Focused microwave irradiation promotes the acid‐free mild and efficient transformation of diarylamines into carbazoles through palladium‐catalyzed oxidative biaryl coupling processes involving a doubleC–H bond activation. The scope of this protocol is demonstrated through the total synthesis of three carbazole natural products, and it is also applied to the synthesis of benzo[b]carbazolequinones.