Synthesis of new chiral imidazolium salts derived from amino acids: their evaluation in chiral molecular recognition
作者:Belén Altava、Dalgi S. Barbosa、M. Isabel Burguete、Jorge Escorihuela、Santiago V. Luis
DOI:10.1016/j.tetasy.2009.03.028
日期:2009.5
A family of new imidazolium salts derivedfrom natural amino acids has been synthesized and tested for NMR enantiodiscrimination, as chiral shift reagents, of carboxylic acids. These imidazolium receptors contain different structural modifications and the splitting of the signals of the acids, after addition of the corresponding CSRs, depends on these structural variables. Compound 8b exhibited the
Chiral bisimidazolium salts derived from amino acids and their palladium(II)- and platinum(II)-biscarbene complexes
作者:Anke Meyer、Maria A. Taige、Thomas Strassner
DOI:10.1016/j.jorganchem.2009.01.036
日期:2009.5
good yields via a one-pot ring closing reaction, followed by esterification. The methylene bridged bisimidazolium iodide salts are accessible in moderate yields. Corresponding palladium(II)- and platinum(II)-NHC complexes could be synthesized and fully characterized, but do not show optical activity. We also report a solid state structure of one of the synthesized palladium(II) biscarbene compounds derived
Synthesis of chiral N-heterocyclic carbene (NHC) ligand precursors and formation of ruthenium(II) complexes for transfer hydrogenation catalysts
作者:Joseph DePasquale、Nicholas J. White、Erin J. Ennis、Matthias Zeller、Joe P. Foley、Elizabeth T. Papish
DOI:10.1016/j.poly.2012.10.010
日期:2013.7
The S enantiomers of ester functionalized NHC ligand precursors, 1-[(2S)-1-ethoxy-3-methyl-1-oxobutan-2-yl]-3-ethyl-1H-imidazol-3-ium bromide (3a) and the methyl ester analog 3b, were synthesized from L-valine and fully characterized. The absolute stereochemistry of the chiral center was confirmed by single crystal X-ray diffraction (for 3a) and enantiopurity (of 3a and 3b) was determined by micellar electrokinetic chromatography. Deprotonation of this NHC ligand precursor (3a or 3b) and coordination to [RuCl2(p-cymene)](2) resulted in the isolation of a monodentate complex (with only NHC coordination) (4a or 4b) and a bidentate complex (5). In the bidentate complex, in addition to NHC coordination, a carboxylate donor group (from in situ hydrolysis of the ester) coordinates to Ru. All ruthenium complexes have been characterized by spectroscopic and analytical methods, plus single crystal X-ray diffraction for 4a and 5. The evidence shows that both Ru complexes are racemic, but with alternate synthetic methods perhaps racemization during complexation of 3a or 3b to metals could be avoided. The ruthenium complexes described herein serve as catalysts for ketone transfer hydrogenation in basic isopropanol. (C) 2012 Elsevier Ltd. All rights reserved.
Huang; Yin; Wu, Asian Journal of Chemistry, 2012, vol. 24, # 11, p. 5405 - 5406