Free-Radical Addition of Dialkyl Phosphites to Branched Fluoro-Olefines

Abstract

We found that under UV-radiation, and without radical initiators, some higher fluoro-olefines regioselectively add dialkyl phosphites to give adducts with high yields. The intermediate phosphonyl substituted fluoroalkyl radicals were observed by ESR-technique and their reactivity was studied:     

N-Heterocyclic carbenes via abstraction of ammonia: 'normal' carbenes with 'abnormal' character

A new ammonia adduct of a N-heterocyclic carbene (NHC) has been isolated, which can be used as a reagent for the synthesis of transition metal carbene complexes. It represents the first example of a 1,2,3-triazolylidene with a 1,2,4-substitution pattern, thus opening a new subclass ('normal' 1,2,3-triazolylidenes) of sterically and electronically tunable NHCs.     

Low Catalyst Loading in Ring‐Closing Metathesis Reactions

An efficient procedure is described for ring‐closing metathesis reactions. A conversion of 95 % for diethyl diallylmalonate in dilute solution could be achieved within a few minutes, reaching TOF=4173 min^?1, with very low loading of commercially available Ru catalysts that contained unsaturated NHC ligands. In general, only 50 to 250 ppm of the catalyst is required to achieve near‐quantitative conversion into a broad variety of 5–16‐membered heterocyclic compounds. The practicality of this procedure was illustrated in the synthesis of 5–8‐membered N‐tert‐butoxycarbonyl (N‐Boc)‐ and N‐para‐toluenesulfonyl (N‐Ts)‐protected cyclic amines and 9–16‐membered lactones. The synthesis of macrocyclic proline‐based lactams required slightly higher catalyst loadings. Along with monocyclic products, oligomeric byproducts, mostly cyclodimers, were isolated and characterized.     

Subterahertz electrodynamics of (TMTSF)2X (X = ClO4, PF6) salts

The terahertz-subterahertz spectra of the complex permittivity and dynamic conductivity of polycrystalline (TMTSF)₂ClO₄ and (TMTSF)₂PF₆ samples are measured quantitatively. The spectra of (TMTSF)₂ClO₄ have absorption lines at frequencies of 7 and 30 cm^?1. The obtained temperature dependences of the line parameters in the range 5–300 K cast some doubt on the earlier concept of their phonon origin. An excitation is detected at temperatures below 20 K in the frequency range near 30 cm^?1, and its nature is related to the activation of a transverse acoustic phonon caused by the folding of the Brillouin zone due to the ordering of noncentrosymmetrical anions below 20 K. An increase in the carrier relaxation rate is found in this temperature range, which indicates a close relation between the electron and phonon subsystems in (TMTSF)₂ClO₄. Sings of additional low-energy excitations that should manifest themselves at frequencies below 1–2 cm^?1 are detected. (TMTSF)₂PF₆ containing centrosymmetrical anions has no absorption lines in the frequency range 3–20 cm^?1 and the temperature range 5–300 K.     

Synthesis of camphor-based chiral P,N-ligands

Russian Journal of Organic Chemistry -     

Antihydrogen formation in low-energy antiproton collisions with excited-state positronium atoms

The convergent close-coupling method is used to obtain cross sections for antihydrogen formation in low-energy antiproton collisions with positronium (Ps) atoms in specified initial excited states with principal quantum numbers n_i ≤?5. The threshold behaviour as a function of the Ps kinetic energy, E, is consistent with the 1/E law expected from threshold theory for all initial states. We find that the increase in the cross sections is muted above n_i =?3 and that here their scaling is roughly consistent with \({n_{i}^{2}}\), rather than the classically expected increase as \({n_{i}^{4}}\).