Pd/Cu-Catalyzed Vinylation of Terminal Alkynes with (2-Bromoethyl)diphenylsulfonium Triflate.

The potential of (2-bromoethyl)diphenylsulfonium triflate to be a powerful vinylation reagent was determined by the Sonogashira cross-coupling reactions with terminal alkynes. The vinylation proceeded smoothly at 25 °C under Pd/Cu catalysis to afford a variety of 1- and 2-unsubstituted 1,3-enynes in moderate to excellent yields. This protocol represents the first application of (2-haloethyl)diphenylsulfonium triflate as a CH═CH2 transfer source in organic synthesis.

Synthesis and Biological Evaluation of CF3 Se-Substituted α-Amino Acid Derivatives.

Several CF3 Se-substituted α-amino acid derivatives, such as (R)-2-amino-3-((trifluoromethyl)selanyl)propanoates (5 a/6 a), (S)-2-amino-4-((trifluoromethyl)selanyl)butanoates (5 b/6 b), (2R,3R)-2-amino-3-((trifluoromethyl)selanyl)butanoates (5 c/6 c), (R)-2-((S)-2-amino-3-phenylpropanamido)-3-((trifluoromethyl)selanyl)propanoates (11 a/12 a), and (R)-2-(2-aminoacetamido)-3-((trifluoromethyl)selanyl)propanoates (11 b/12 b), were readily synthesized from natural amino acids and [Me4 N][SeCF3 ]. The primary in vitro cytotoxicity assays revealed that compounds 6 a, 11 a and 12 a were more effective cell growth inhibitors than the other tested CF3 Se-substituted derivatives towards MCF-7, HCT116, and SK-OV-3 cells, with their IC50 values being less than 10 µM for MCF-7 and HCT116 cells. This study indicated the potentials of CF3 Se moiety as a pharmaceutically relevant group in the design and synthesis of novel biologically active molecules.

Fluorine-Containing Inhalation Anesthetics: Chemistry, Properties and Pharmacology.

Studies on fluorinated inhalation anesthetics, including synthesis, physical chemistry and pharmacology, have been summarized in this review. Retrospecting the history of inhalation anesthetics revealed their increasing reliance on fluorine and ether structures. Halothane causes a rare but severe immune-based hepatotoxicity, which was replaced by enflurane in the 1970s. Isoflurane replaced enflurane in the 1980s, showing modest advantages (e.g. lower solubility, better metabolic stability, and without convulsive predisposition). Desflurane and sevoflurane came into use in the 1990s, which are better anesthetics than isoflurane (less hepatotoxicity, lower solubility, and/or markedly decreased pungency). However, they are still less than perfect. To gain more ideal inhalation anesthetics, a large number of fluorinated halocarbons, polyfluorocycloalkanes, polyfluorocycloalkenes, fluoroarenes, and polyfluorooxetanes, were prepared and their potency and toxicity were evaluated. Although the pharmacology studies suggested that some of these agents produced anesthesia, no further studies were continued on these compounds because they showed obvious lacking as anesthetics. Moreover, the anesthetic activity cannot be simply predicted from the molecular structures but has to be inferred from the experiments. Several regularities were found by experimental studies: 1) the potency and toxicity of the saturated linear chain halogenated ether are enhanced when its molecular weight is increased; 2) the margin of safety decreases and the recovery time is prolonged when the boiling point of the candidate increases; and 3) compounds with an asymmetric carbon terminal exhibit good anesthesia. Nevertheless, the development of new inhalation anesthetics, better than desflurane and sevoflurane, is still challenging not only because of the poor structure/activity relationship known so far but also due to synthetic issues.

Base-Mediated O-Arylation of Alcohols and Phenols by Triarylsulfonium Triflates.

A mild and efficient protocol for O-arylation of alcohols and phenols (ROH) by triarylsulfonium triflates was developed under transition-metal-free conditions. Various alcohols, including primary, secondary and tertiary, and phenols bearing either electron-donating or electron-withdrawing groups on the aryl rings were smoothly converted to form the corresponding aromatic ethers in moderate to excellent yields. The reactions were conducted at 50 or 80 °C for 24 h in the presence of a certain base and showed good functional group tolerance. The base-mediated arylation with asymmetric triarylsulfonium salts could selectively transfer the aryl groups of sulfoniums to ROH, depending on their inherent electronic nature. The mechanistic studies revealed that the reaction might proceed through the nucleophilic attack of the in situ formed alkoxy or phenoxy anions at the aromatic carbon atoms of the C-S bonds of triarylsulfonium cations to furnish the target products.

Transition-Metal-Free N-Arylation of Amines by Triarylsulfonium Triflates.

A simple and efficient method for transition-metal-free N-arylation of various amines by triarylsulfonium triflates is described. Both aliphatic and aromatic amines were smoothly converted at 80 °C in the presence of tBuOK or KOH to give the corresponding mono N-arylated products in good to high yields. The molar ratios of the reactants and the choice of bases had a big effect on the reaction. When a large excess of [Ph3 S][OTf] and tBuOK were employed for primary amines under the standard conditions, the bis(N-phenyl) products were predominantly formed. This method was also applicable to the synthesis of bioactive N-phenyl amino acid derivatives. The control experiments, the deuterium labelling study, and the presence of regioisomers of N-arylated products when using 4-substituted triarylsulfonium triflates suggested that the reaction might proceed through an aryne intermediate. The present protocol demonstrated that triarylsulfonium salts are versatile arylation reagents in the construction of CAr -N bonds.