Pd-Catalyzed Enantioselective Ring Opening/Cross-Coupling and Cyclopropanation of Cyclobutanones.

A palladium-catalyzed enantioselective sequential ring-opening/cross-coupling of cyclobutanones is disclosed that provides chiral indanones bearing C3-quaternary stereocenters. The reaction process involves palladium-catalyzed nucleophilic addition of cyclobutanones and aryl halides, enantioselective ß-carbon elimination, and intermolecular trapping of a transient σ-alkylpalladium complex with boronic acids. Alternatively, an intramolecular cyclopropanation is realized through C-H bond functionalization in the absence of external coupling reagents, affording chiral cyclopropane-fused-indanones in good yields and enantioselectivity.

Benzyl Deuteriodifluoromethyl Sulfoxide: An Easily Accessible and Stable Reagent for Direct Deuterodifluoromethylthiolation.

A new, stable and scalable reagent based on a sulfoxide skeleton for direct deuteriodifluoromethylthiolation has been developed. The reagent displays excellent reactivities toward Tf2O promoted C-H deuteriodifluoromethylthiolation of electron-rich arenes, indoles, alkenes, and intramolecular lactonization of 2-alkynylbenzoates. Moreover, high deuteration rates and good to excellent yields were achieved under metal-free reaction conditions. As a result, a wide range of deuteriodifluoromethylthilolated compounds were prepared, enabling further applications in drug discovery.

Deviant mass shift of hydrated product ions from sodiated beta-anilinodidrochalcones using an ion-trap mass spectrometer.

The fragmentation reactions of sodiated beta-anilinodidrochalcones have been investigated by electrospray ionization multi-stage mass spectrometry (ESI-MS(n)). The fragment ion of sodiated N-benzylidenebenzenamine (P1) easily undergoes ion-molecule reactions with the residual ESI solvent molecules (H2O and CH3OH) in the vacuum system, as verified by MS3 and accurate MS analysis. The formed hydrated ions appear as an unusual leading peak in the profile spectrum, which results in a deviant decreasing mass shift of almost 1 Da. Density functional theory calculations indicate that P1 easily associates with H2O without any energy barrier. Thus, the hydrated P1 exists partially as a loose system of P1 and H2O, which provides a reasonable explanation for the decreasing mass shift of the solvated P1. The above results are important in obtaining structural information from MS(n) spectra and preventing erroneous data interpretation for the analogous adducts.

Molecular assembly of an achiral phosphine and a chiral primary amine: a highly efficient supramolecular catalyst for the enantioselective Michael reaction of aldehydes with maleimides.

A combined catalyst system of a cinchonidine-derived primary amine and triphenylphosphine (CD-NH2 /PPh3 ) exhibited high catalytic performance in the Michael reaction of aldehydes with maleimides, thereby affording the corresponding functionalized aldehydes in excellent yields (up to 99 %) and enantioselectivities (>99 % ee). More interestingly, the significance of the phosphine in enhancing the enantioselectivities in the chiral-primary-amine-catalyzed Michael reaction was revealed. Furthermore, we explored the origin of the reaction mechanism in the Michael addition promoted by the dual organocatalytic system. On the basis of experimental results and spectroscopic analysis, such as UV/Vis, fluorescence emission (FL), NMR, and circular dichroism (CD) spectroscopy, as well as ESI-MS, we found that the molecular assembly of phosphine and primary amine played a crucial role in this enantioselective reaction, in which a possible supramolecular complex was formed as an effective chiral catalyst through noncovalent molecular interactions of a cinchona alkaloid-derived primary amine with triphenylphosphine.

Silicon-based Lewis acid assisted cinchona alkaloid catalysis: highly enantioselective aza-Michael reaction under solvent-free conditions.

The study showed that a combination of an achiral silicon-based Lewis acid and chiral Lewis base, such as iodotrimethylsilane (TMSI) and cinchonine, generated a highly enantioselective catalyst system under solvent-free conditions which gave aromatic ß-amino ketones with up to >99% ee. Mechanistic studies demonstrate the enhanced asymmetric induction may be due to the combined and competitive activation of a carbonyl moiety of chalcone with cinchonine and the silicon-based Lewis acid in the aza-Michael reaction.

Resveratrol and its oligomers from wine grapes are selective (1)O2 quenchers: mechanistic implication by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry and theoretical calculation.

Resveratrol and its oligomers, abundantly present in wine grapes, are believed to be effective phytoalexins for the phenomenon "French paradox" partially by virtue of their powerful antiradical properties. EPR spin-trapping technique was utilized, demonstrating all polyphenols were selective (1)O2 quenchers but not effective (•)OH and O2(•¯) scavengers. On the basis of the HPLC-ESI-MS(2) analysis for the simulated reactions of polyphenols with (1)O2, the molecular weights of the resulting photochemical products were 14 or 28 Da higher than those of their substrates. No fragment C2H2O (42 Da), which was rather distinctive of the resorcinol rings in these cases, had been observed, whereas their MS/MS spectra displayed characteristic neutral fragments including carbon monoxide (CO, 28 Da) and 2-hydroxy[1,4]benzoquinone (C6H4O3, 124 Da). Finally, PM3 semiempirical calculations and HR-FTICR-MS experiments were performed, supporting the assertion that their quenching mechanism involved physical and chemical pathways. Chemical quenching underwent an endoperoxide intermediate form to generate quinones.