RESUMO
A Lewis acid-catalyzed tandem reaction strategy for the construction of a dihydrophenalene-lactone tetracyclic skeleton has been disclosed. Starting with 2-naphthol-tethered ketones and active methylene esters, the tandem reaction catalyzed by Sc(OTf)3 proceeded well to afford an array of dihydrophenalene-fused lactones with moderate to high efficiency and diastereoselectivity. Moreover, the synthetic utility of this protocol was demonstrated by easy gram-scale preparation and diverse product transformations.
RESUMO
Protonated water-hydrogen clusters [H+(H2O)n·m(H2)] present an interesting model for fundamental water research, but their formation and isolation presents considerable experimental challenges. Here, we report the detection of [H+(H2O)n·m(H2)] (2 ≤ n ≤ 3, m ≤ 2) clusters alongside protonated water clusters H+(H2O)n (2 ≤ n ≤ 3) in a linear ion trap mass spectrometer under two different experimental conditions: (1) when water vapor was ionized by +5.5 kV ambient corona discharge in front of the mass spectrometer inlet; (2) when isolated H+(H2O)n clusters were exposed to H2 gas inside the linear trap. Chemical assignment of [H+(H2O)n·m(H2)] clusters was confirmed using reference experiments with isotopically labeled water and deuterium. Also, the formation of H2 gas in the corona discharge area was indicated by a flame test. Overall, our findings clearly indicate that [H+(H2O)n·m(H2)] clusters can be produced at room temperature through the association of protonated water clusters H+(H2O)n with H2 gas, without any cooling necessary. A mechanism for the formation of the protonated water-hydrogen complexes was proposed. Our results also suggest that the association of water ions with H2 gas may play a notable role in corona discharge ionization processes, such as atmospheric pressure chemical ionization, and may be partially responsible for the stabilization of reactive radical species occasionally reported in corona discharge ionization experiments.