Nucleophilic trifluoromethylation of carbonyl compounds and disulfides with trifluoromethane and silicon-containing bases

Provided that DMF (or another N,N-dialkylformamide) is present in the reaction medium, at least in a catalytic amount, fluoroform trifluoromethylates efficiently carbonyl compounds, even enolizable ones, when opposed to (TMS)(2)N(-) M(+), generated in situ from N(TMS)(3) and M(+) F(-) or RO(-) Na(+). When F(-) is used in a catalytic amount, silylated alpha-(trifluoromethyl)carbinols are obtained: in this case, the four-component system HCF(3)/N(TMS)(3)/catalytic F(-)/catalytic DMF behaves like the Ruppert's reagent, especially as far as nonenolizable carbonyl compounds are concerned (CF(3)SiMe(3) remains more efficient for enolizable carbonyl compounds). This process involves an adduct between DMF and (-)CF(3) which is the true trifluoromethylating agent. In the same way, fluoroform efficiently trifluoromethylates disulfides and diselenides when deprotonated with a strong base selected from t-BuOK or N(SiMe(3))(3)/Me(4)NF (or TBAT). t-BuOK is more adapted to the trifluoromethylation of aryl disulfides whereas N(SiMe(3))(3)/F(-) is well suited to that of aliphatic disulfides.     

Artificial metalloenzymes: The powerful alliance between protein scaffolds and organometallic catalysts

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Phosphinoferrocenylaminophosphines as novel and practical ligands for asymmetric catalysis

[structure: see text] A new series of ligands with a novel phosphine-aminophosphine ligation design as depicted in structure 1 has been prepared on a ferrocenylethyl backbone. These BoPhoz ligands of structure 2 have afforded exceedingly high activity and enantioselectivity in the rhodium-catalyzed asymmetric hydrogenation of dehydro-alpha-amino acid derivatives, itaconic acids, and alpha-ketoesters. These air-stable ligands are readily prepared from cost-effective and non-pyrophoric intermediates.     

Heteroatomic molecular clusters derived from Group 15 Zintl ion cages: synthesis and isolation of [M2(HP7)2](2-) (M=Ag, Au), two novel cluster anions exhibiting metallophilic interactions

Ethylenediamine (en) solutions of K(3)P(7) and 2,2,2-crypt (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) were reacted with the homoleptic group 11 complexes [M(nbe)(3)][SbF(6)] (M = Ag, Au; nbe = norbornene) yielding two novel cluster anions, [M(2)(HP(7))(2)](2-), both of which were isolated in low crystalline yields as [K(2,2,2-crypt)](2)[M(2)(HP(7))(2)] (M = Ag (1) and Au (2)). Optimization of the reaction conditions by incorporation of a proton source (ammonium tetraphenylborate) and the replacement of the light-sensitive nbe adducts of silver and gold with the chloride salts MCl (M = Ag, Au) was found to greatly increase the yield and purity in which 1 and 2 were isolated. Compounds 1 and 2 were characterized by single crystal X-ray diffraction, electrospray ionization mass-spectrometry (ESI- MS), elemental analysis, and (1)H and (31)P NMR spectroscopy. Density functional theory (DFT) calculations on the cluster anions were also conducted.     

The effect of stereochemistry on the mass spectra of the bis(trimethyl-silyl) esters of maleic and fumaric acids

The mass spectra of the bis(trimethylsilyl) esters of maleic and fumaric acids provide a simple and particularly striking example of the influence of stereochemistry on the electron-impact-induced fragmentation of organic molecules. The results provide evidence for the structural significance of the m/e 147 ion, which is considerably more intense in the maleate spectrum than in the fumurate spectrum.     

Transmission of terahertz radiation using a microstructured polymer optical fiber

A hollow-core microstructured polymer optical fiber was analyzed in the terahertz (THz) region. Spectral analysis of time domain data shows propagation of THz waves in both the hollow-core and the microstructured cladding with a time delay of approximately 20 ps. The frequency range and shift of the transmission bands between different sized waveguides suggested photonic bandgap or resonant guidance. Finite-difference time domain calculations agree relatively well to the experimental transmission results. Propagation losses were estimated to be as low as 0.9 dB/cm.     

Aryne-Enabled C−N Arylation of Anilines

Anilines are potentially high-value arylating agents, but are limited by the low reactivity of the strong C−N bond. We show that the reactive intermediate benzyne can be used to both activate anilines, and set-up an aryl transfer reaction in a single step. The reaction does not require any transition metal catalysts or stoichiometric organometallics, and establishes a metal-free route to valuable biaryl products by functionalizing the aniline C−N bond.