84 research outputs found
Mustard carbonate analogues
Sulfur and nitrogen (half-)mustard carbonate analogues are a new class of compounds, easily synthesized
by methoxycarbonylation reaction of the parent alcohols with dialkyl carbonates. In this work, their
reactivity as novel, green electrophiles is reported. Reactions have been conducted in autoclave conditions
at high temperature (180 °C), under pressure and in absence of any base, as well as, in neat at atmospheric
pressure, lower temperature (150 °C) and in the presence of a catalytic amount of a base. Several nucleophiles
have been investigated resulting, in some cases, in unexpected compounds, i.e., six-membered heterocycle
piperidine. Reaction mechanism and kinetics have been studied confirming that these compounds retain the
anchimeric effect of their mustard gas analogues, without being toxic. Noteworthy, a symmetrical nitrogen
mustard carbonate has also been employed as reagent in the preparation of a new family of macrocycles i.e.,
azacrowns, before not easily accessible
Dialkyl Carbonates in the Green Synthesis of Heterocycles
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 (BAc2/BAl2 mechanism). Cyclic carbamates, namely
1,3-oxazin-2-ones, were prepared employing DACs as carbonylating agents, either
by BAc2/BAl2 mechanism or through a double BAc2 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
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