Cross-coupling of mesylated phenol derivatives with potassium alkoxymethyltrifluoroborates

Cross-coupling of mesylated phenol derivatives with various potassium alkoxymethyltrifluoroborates has been achieved. The corresponding aryl and heteroaryl alkoxymethyl compounds have been obtained with equal facility with both electron-rich and electron-poor substituents on the activated alcohol.     

Stereoselective organocatalytic one-pot α,α-bifunctionalization of acetaldehyde by a tandem Mannich reaction/electrophilic amination

The first asymmetric organocatalyzed one-pot α,α-bifunctionalization of acetaldehyde with two different electrophiles is described. A diarylprolinol silyl ether-catalyzed reaction of acetaldehyde with an imine and di-tert-butyl azodicarboxylate affords syn-2,3-diaminoalcohols with excellent ee values of up to 98%. This methodology was successfully applied to the synthesis of a chiral α,β-diaminocarboxylic acid.     

Liquid chromatographic retention of homologous alkanes in the two states of C18-bonded reversed phase silicas

Summary LiChrosorb Si100 densely grafted with octadecylmonofunctional reagents and the similar commerical LiChrosorb RP 18 have been studied in RP-HPLC, with water-methanol mobile phases at different temperatures. They exhibit a phase transition revealing two different states of bonded film as we have previously shown on densely grafted C18 or C22 macroporous silicas.The measurement of the capacity factors of the alkane homologous series indicated a discontinuity in the plot (logK, N) at a critical number whose value is dependent on temperature. Two different forms of these curves can be observed above and below the transition, revealing the influence of bonded film state on the retention mechanism.     

Etudes des sélénophènes mono et bisubstitués par Résonance Magnétique de 1H et de 13C

Proton and carbon magnetic resonance spectra of mono-and disubstituted selenophenes are investigated. The proton chemical shifts are discussed in terms of magnetic anisotropy and electric field effects of the substituents, with a view to studying the conformational equilibrium of the carbonyl group. π Electronic charges, computed by the PPP method, are correlated with the proton and carbon chemical shifts. The coupling constants between ¹³C and ¹H (1, 2 or 3 bonds) and ¹³C? ⁷⁷Se are shown to be good structural parameters and a set of substituent additivity constants is calculated.     

Spectrum of lattice gauge theories with fermions from a 1/d expansion at strong coupling

We study the strong coupling limit of U(N) or SU(N) gauge theories with fermions on a lattice. The integration over the gauge and fermion degrees of freedom is performed by analytic methods, leading to a partition function in terms of localized meson and baryon fields. A method for deriving a systematic expansion in the inverse of the space-time dimension of the corresponding Green functions is developed. It is applied to the study of spontaneous breakdown of chiral symmetry, which occurs for any U(N) or SU(N) theory with fermions in the fundamental representation. Meson and baryon spectra are then computed, and found to be in close agreement with those obtained by numerical methods at finite coupling. The pion decay constant is estimated.     

Gluon jet in deep inelastic muon scattering

We study the quark and gluon final state in deep inelastic μ-scattering. For a hadron observed at sufficiently large angleθ _h with respect to the virtual photon direction, and sufficiently large energy fractionz _h , this final state dominates the cross-section. Moreover, at the same time, most events in this regime are due to the fragmentation of the quark. In such cases the position of the gluon in phase space is determined, the quark acting as a trigger for gluon jet detection. We demonstrate that in the rest frame of the final quark and gluon, the gluon is energetic and well separated from quark and target fragments. We study the boost from the lab to this frame, and give expressions for the most probable boost in terms ofθ _h andz _h . This study should lead to a convenient visualization of the gluon jet.