Novel C2-symmetric chiral ligands: enantioselective transformation of cyclic 1,2-diols into 1,2-bis(phenylsulfenyl) and 1,2-bis(phenylselenyl) derivatives
作者:Elżbieta Wojaczyńska、Jacek Skarżewski
DOI:10.1016/j.tetasy.2008.02.001
日期:2008.3
Chiral C-2-symmetric S,S- and Se,Se-donating ligands as well as the C-1 mixed S,Se-donating ligands were prepared from optically active 1,2-cyclohexanediol and 1,2-cyclopentanediol via the respective S(N)2 reactions. The bis(chalcogen) ligands obtained effectively catalyze the asymmetric allylic alkylation with enantioselectivities of up to 50% ee. (C) 2008 Elsevier Ltd. All rights reserved.
77Se,13C and1H NMR spectra of phenylselenenylcycloalkanes, -cycloalkenes and some of their selenoxides and125Te NMR of a tellurium analogue
作者:Helmut Duddeck、Petra Wagner、Armin Biallaß
DOI:10.1002/mrc.1260290310
日期:1991.3
The 77Se, 13C and 1H NMR spectra of 46 mostly new compounds with phenylselenenyl groups attached to carbocycles and of three new corresponding selenoxides and the 125Te NMR of phenyltellurenylcyclohexane are reported. Substituent effects on the chemical shifts of these nuclei are compiled and discussed in terms of the configuration and conformation. Low-temperature NMR spectra of some cyclohexane derivatives allowed the evaluation of thermodynamic data, such as A values of the PhSe, PhSe(O) and PhTe groups.