AUTHOR=Tundo Pietro , Musolino Manuele , Aricò Fabio 

TITLE=Dialkyl Carbonates in the Green Synthesis of Heterocycles

JOURNAL=Frontiers in Chemistry

VOLUME=7

YEAR=2019

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2019.00300

DOI=10.3389/fchem.2019.00300

ISSN=2296-2646

ABSTRACT=<p>This review focuses on the use of dialkyl carbonates (DACs) as green reagents and solvents for the synthesis of several 5- and 6-membered heterocycles including: tetrahydrofuran and furan systems, pyrrolidines, indolines, isoindolines, 1,4-dioxanes, piperidines, and cyclic carbamates. Depending on the heterocycle investigated, the synthetic approach used was different. Tetrahydrofuran systems, pyrrolidines, indolines, isoindoline, and 1,4-dioxanes were synthesized using dimethyl carbonate (DMC) as sacrificial molecule (B<sub>Ac</sub>2/B<sub>Al</sub>2 mechanism). Cyclic carbamates, namely 1,3-oxazin-2-ones, were prepared employing DACs as carbonylating agents, either by B<sub>Ac</sub>2/B<sub>Al</sub>2 mechanism or through a double B<sub>Ac</sub>2 mechanism. Piperidines were synthetized taking advantage of the anchimeric effect of a new family of dialkyl carbonates, i.e., mustard carbonates. Finally, in the case 5-hydroxymethylfurfural (HMF), DMC has been employed as efficient extracting solvent of this extensively investigated bio-based platform chemical from the reaction mixture. These synthetic approaches demonstrate, once again, the great versatility of DACs and their—yet to be fully explored—potential as green reagents and solvents in the synthesis of heterocycles.</p>