Synthesis 2020; 52(04): 619-628
DOI: 10.1055/s-0039-1691069
paper
© Georg Thieme Verlag Stuttgart · New York

A Green Nanopalladium-Supported Catalyst for the Microwave-Assisted Direct Synthesis of Xanthones

H. Sebastián Steingruber
,
Pamela Mendioroz
,
Alejandra S. Diez
,
Darío C. Gerbino
Instituto de Química del Sur, INQUISUR (CONICET-UNS), Departamento de Química, Universidad Nacional del Sur, Avenida Alem 1253, 8000 Bahía Blanca, Argentina   Email: dgerbino@uns.edu.ar
› Author Affiliations
This work was partially 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. H.S.S. and P.M. thank CONICET and ANPCyT for a doctoral fellowship. D.C.G. is a research member of CONICET. Thanks are also given to ANPCyT for the purchase of the SPECS multitechnique analysis instrument (PME8-2003).
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Publication History

Received: 03 September 2019

Accepted after revision: 10 October 2019

Publication Date:
30 October 2019 (online)


Abstract

We report an efficient, selective, rapid and eco-friendly protocol for the one-step synthesis of a small xanthone library via an intermolecular catalytic coupling from readily available salicylaldehydes and 1,2-dihaloarenes under ligand-free conditions. To achieve this advantageous direct annulation, we used a novel recoverable palladium nanocatalyst supported on a green biochar under microwave irradiation. Unlike other existing palladium-based approaches, our synthetic strategy showed a greater operational simplicity, drastic reduction in reaction times, and an excellent tolerance to diverse functional groups. The reaction proceeds in very good yields and with high regioselectivity. The novel heterogeneous catalyst can be recycled and reused up to four times without significant loss of activity.

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