- On enantioselective separation of phenoxypropionates using permethylated β-cyclodextrin HPLC and GC columns
-
Investigations on chiral phenoxypropionates using permethylated β-cyclodextrin HPLC and GC columns showed a decrease in enantioselective separation efficiency from mecoprop-methyl and dichlorprop-methyl to the threefold chlorinated fenoprop-methyl. This corresponded to decreasing electron density in the aromatic system due to the increasing negative inductive effect of 3 chlorine substituents. Investigation on methyl-(RS)-2-(2,4-dichloro-3,6-dinitrophenoxy)-propionate confirmed the influence of electrophilic substituents while determination of ethyl-(RS)-2-methoxypropionate emphasized the necessity of an aromatic system for enantioselective separation on a-cyclodextrin stationary phases. For fenoprop-methyl as well as for the aryloxyphenoxypropionates diclofop-methyl and fluazifop-butyl, reversed phase HPLC showed higher separation performance than high resolution capillary GC.
- Weber,Kreuzig,Bahadir
-
-
Read Online
- Phosphane ligands with two binding sites of differing hardness for enantioselective Grignard cross coupling
-
A series of new, chiral phosphanes is presented, individual members of which were designed to serve as ligands in transition-metal mediated asymmetric Grignard cross coupling reactions. These ligands are characterized by a side chain containing one or two oxygen atoms with the capacity to act as binding sites for the incoming Grignard reagent. A number of structural parameters for the compounds was varied to learn about the reaction mechanism. Most of the ligands were tested in two cross coupling reactions, the formation of 3-phenylbut-1-ene and of 2,2′-dimethyl-1,1′-binaphthyl, respectively. Although both systems gave modest enantiomeric excesses it was not possible to make a comparison of their respective abilities.
- Terfort, Andreas,Brunner, Henri
-
p. 1467 - 1479
(2007/10/03)
-
- Enantioselective cyclopropane syntheses using the chiral carbene complexes (SFe)- and (RFe)-C5H5(CO)(PR3)Fe=CHCH 3+. A mechanistic analysis of the carbene transfer reaction
-
Enantiomerically pure or enriched iron-carbene complexes of the type C5H5(CO)(PR3)Fe=CHCH3+ have been prepared by three routes: (a) Diastereomeric acyl complexes C5H5(CO)(PPhsub
- Brookhart, Maurice,Liu, Yumin,Goldman, Emma W.,Timmers, Debra A.,Williams, Gregory D.
-
p. 927 - 939
(2007/10/02)
-