588701-59-1Relevant articles and documents
Asymmetric induction afforded by chiral azolylidene N-heterocyclic carbenes (NHC) catalysts
Strand, Ragnhild B.,Helgerud, Trygve,Solvang, Tina,Dolva, Amund,Sperger, Christian A.,Fiksdahl, Anne
, p. 1350 - 1359,10 (2012/12/11)
Screening studies of new chiral imidazolium and triazolium based NHC salts I-VIII as ligands in asymmetric organometallic catalysis and as organocatalysts showed that these catalysts efficiently promoted the reactions. Moderate enantioselectivities (55-57% ee) were obtained in the asymmetric Cu-NHC catalysed conjugate additions of diethylzinc to cyclohexenone, in accordance with most previous studies. The chiral induction afforded in the gold(I)-NHC catalysed cyclopropanation reactions was low (28% ee). However, these results represent the first reported chiral gold(I)-NHC catalysed olefin cyclopropanation. The NHC-organocatalysed asymmetric cross-annulation of cinnamaldehyde and trifluoroacetophenone gave lower enantioselectivity (50% ee) but higher yields of the γ-lactone product relative to previous reports. The enantioselectivities obtained varied considerably, even within a group of structurally closely related NHCs. This study demonstrates the challenge of designing NHCs with a general ability to induce asymmetry in a broader range of reactions.
Imidazolium-oxazoline salts in ruthenium-catalyzed allylic substitution and cross metathesis of formed branched isomers
Ammar, Hamed Ben,Hassine, Bechir Ben,Fischmeister, Cedric,Dixneuf, Pierre H.,Bruneau, Christian
experimental part, p. 4752 - 4756 (2011/02/28)
Imidazolium-oxazoline chlorides have been prepared from chloroacetonitrile and used to generate bidentate mixed NHC-oxazoline ligands for ruthenium-catalyzed substitution of cinnamyl chloride by phenols. These ligands associated to [RuCp*(MeCN)3][PF6] promote allylic substitution reactions at room temperature with high regioselectivity in favour of the branched isomers giving terminal alkenes. These allylic ethers have been involved in further ruthenium-catalyzed cross metathesis reactions with electron-deficient olefins to give unsaturated esters and aldehydes. NHC-oxazoline ligands associated to the Cp*RuII moiety generate catalysts that orientate the nucleophilic allylic substitution of cinnamyl chloride by phenols towards the regioselective formation of branched products, which, on reaction with Hoveyda(II) catalyst, lead to cross metathesis, and unsaturated functional compounds.
