Convenient One-Pot Synthesis of 9H-Carbazoles by Microwave Irradiation Employing a Green Palladium-Based Nanocatalyst
H. Sebastián Steingruber
a
Instituto de Química del Sur, INQUISUR (CONICET-UNS), Departamento de Química, Universidad Nacional del Sur, Avenida Alem 1253, 8000 Bahía Blanca, Argentina
,
Pamela Mendioroz
a
Instituto de Química del Sur, INQUISUR (CONICET-UNS), Departamento de Química, Universidad Nacional del Sur, Avenida Alem 1253, 8000 Bahía Blanca, Argentina
,
María A. Volpe
b
Planta Piloto de Ingeniería Química (PLAPIQUI-CONICET), Camino La Carrindanga Km 7, 8000 Bahía Blanca, Argentina
,
Darío C. Gerbino∗
a
Instituto de Química del Sur, INQUISUR (CONICET-UNS), Departamento de Química, Universidad Nacional del Sur, Avenida Alem 1253, 8000 Bahía Blanca, Argentina
› Author AffiliationsThis work was generously supported by the National Council of Scientific and Technical Research (Consejo Nacional de Investigaciones Científicas y Técnicas; CONICET), the National Agency for Scientific and Technological Promotion (Agencia Nacional de Promoción Científica y Tecnológica; ANPCyT), and the Universidad Nacional del Sur (Secretaría General de Ciencia y Tecnología, Universidad Nacional del Sur; SGCyT-UNS), Argentina.
Dedicated to Professor Julio C. Podestá on the occasion of his 80th birthday
Abstract
An efficient palladium-catalyzed tandem reaction for the one-pot synthesis of 9H-carbazoles under microwave irradiation is developed. This approach involves a sequential Buchwald–Hartwig amination and a direct arylation from affordable and inexpensive anilines and 1,2-dihaloarenes. For the development of this purpose, a novel and magnetically recoverable palladium nanocatalyst supported on a green biochar under ligand-free conditions is used. Compared to other existing palladium-based protocols, the present synthetic methodology shows a drastic reduction in reaction times and excellent compatibility with different functional groups allowing to obtain a small library of 9H-carbazoles in high yields and with good regioselectivity. This procedure represents the first example in the direct synthesis of carbazoles using a heterogeneous palladium nanocatalyst from commercial precursors. To examine the application of this protocol, a direct and scalable synthesis of the bioactive carbazole alkaloid clausenalene from commercially available starting materials is described.
12b
Sharma N,
Sharma UK,
Van der Eycken EV.
Microwave-Assisted Organic Synthesis: Overview of Recent Applications. In Green Techniques for Organic Synthesis and Medicinal Chemistry.
Zhang W,
Cue BW.
Wiley; Hoboken: 2018: 441-468