AUTHOR=Tabasso Silvia , Calcio Gaudino Emanuela , Acciardo Elisa , Manzoli Maela , Bonelli Barbara , Cravotto Giancarlo 

TITLE=Microwave-Assisted Protocol for Green Functionalization of Thiophenes With a Pd/β-Cyclodextrin Cross-Linked Nanocatalyst

JOURNAL=Frontiers in Chemistry

VOLUME=8

YEAR=2020

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2020.00253

DOI=10.3389/fchem.2020.00253

ISSN=2296-2646

ABSTRACT=<p>Microwaves (MW) are often the most efficient, in terms of heat exchange and conversion rate, of all the energy sources used to promote chemical reactions thanks to fast volumetric dielectric heating, and metal-catalyzed synthetic reactions under heterogeneous conditions are an eloquent example. We herein report a MW-assisted green protocol for the C-H arylation of thiophenes with substituted aryl halides. This sustainable protocol carried out in γ-valerolactone (GVL) is catalyzed by Pd nanoparticles embedded in cross-linked β-cyclodextrin. In view of the excellent results achieved with activated substrates, the one-pot synthesis of a 4(<italic>3H</italic>)-quinazolinone derivative has been accomplished. A pressure-resistant MW reactor, equipped with multiple gas inlets, was used for sequential (i) C-H arylation, (ii) reduction, and (iii) carbonylation in the presence of the same catalyst, but under different gas atmospheres. The robust heterogeneous Pd catalyst showed limited metal leaching in GVL, making this an efficient MW-assisted process with high atom economy.</p>