The straightforward oxidation of electron-rich arenes, namely phenols, naphthols and anisole derivatives under mild reaction conditions is described by means of the use of environmentally benign HFIP-UHP system. The corresponding quinones or hydroxylated arenes, were obtained in moderate to good yields.Quinone derivatives constitute an important class of organic compounds present in several natural products that exhibit a wide range of applications in medicinal chemistry or biochemistry, 1 also playing an important role in some biological redox processes. 2 For example, some of these derivatives exhibit a demonstrated biological activity as it is the case of those representative examples shown in Figure 1.
The oxidative cleavage of indoles (Witkop oxidation) involving the use of H2O2 or urea hydrogen peroxide in combination with a polar solvent has been described. Among these solvents, 1,1,1,3,3,3‐hexafluoroisopropanol (HFIP) stands out as the one affording the corresponding 2‐ketoacetanilides generally in higher yields The protocol described has also enabled the oxidation of different pyrroles and furans derivatives. Furthermore, the procedure was implemented in a larger‐scale and HFIP was distilled from the reaction mixture and reused (up to 4 cycles) without a significant detriment in the reaction outcome, which remarks its sustainability and applicability.
In the present work, the employment of fluorinated alcohols, specifically 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), as solvent and promoter of the catalyst-free synthesis of substituted tetrahydrofuranes through the addition of electron-rich alkenes to epoxydes is described. The unique properties of this fluorinated alcohol, which is very different from their non-fluorinated analogs, allows carrying out this new straightforward protocol under smooth reaction conditions affording the corresponding adducts in moderate yields in the majority of cases. Remarkably, this methodology has allowed the synthesis of new tetrahydrofuran-based spiro compounds as well as tetrahydrofurobenzofuran derivatives. The scope and limitations of the process are also discussed. Mechanistic studies were also performed pointing towards a purely ionic or a SN2-type process depending on the nucleophilicity of the alkene employed.
The straightforward synthesis of N,N-disubstituted formamides using 1,1,1,3,3,3hexafluoroispropanol (HFIP) and H 2 O 2 combination is described. The unique features of HFIP allowed the utilization of a green oxidant such as H 2 O 2 and the products, arising from an oxidation-rearrangement sequence, were obtained in good to high yields under smooth reaction conditions.
INTRODUCTION
The oxidative dehydrogenation of N‐heterocyclic compounds by using H2O2 as oxidant in combination with polar solvents such as 1,1,1,3,3,3‐hexafluoroisopropanol (HFIP) and H2O is described. Among these two solvents, the best yields for the heteroaromatic compounds were generally achieved in HFIP. However, it is remarkable, that the use of a non toxic solvent such as H2O gave such good yields. Furthermore, the procedure was implemented in larger‐scale and HFIP was distilled from the reaction mixture and reused (up to 5 cycles) without a significant detriment in the reaction outcome.
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