92587-21-8Relevant academic research and scientific papers
Chemo- And stereoselective reduction of β-keto-α-oximino nitriles by using baker's yeast
Mo, Kilwoong,Kang, Soon Bang,Kim, Youseung,Lee, Yong Sup,Lee, Jae Wook,Keum, Gyochang
, p. 1137 - 1143 (2015/02/19)
The baker's yeast mediated reduction of β-keto-α-oximino nitriles 3 at 20 ° C gave β-hydroxy-α-oximino nitriles 4 in high yields with high enantiomeric purity [enantiomeric excess (ee) values >99%]. At room temperature, the same reaction afforded the product in a slightly lower yield. The β-hydroxy-α-oximino nitriles 4 were obtained as single stereoisomers according to chiral GC-MS analyses and the 1H and 19F NMR spectra of the corresponding Mosher esters. The abso-lute stereochemistry of alcohol 4a was determined by hydrolysis of its oximino nitrile group followed by conversion into its corresponding α-hydroxy ester. The β-hydroxy-α-oximino nitrile products were further submitted to oxime- and nitrileselective transformations. This chemo- and stereoselective reduction can be used to generate important chiral building blocks.
Stereoselective synthesis of functionalised triol units by SnCl4 promoted allylation of α-benzyloxyaldehydes: Crucial role of the stoichiometry of the Lewis acid
Dubost, Christophe,Leroy, Bernard,Markó, Istvan E.,Tinant, Bernard,Declercq, Jean-Paul,Bryans, Justin
, p. 7693 - 7704 (2007/10/03)
Enantiomerically pure syn-anti and syn-syn configured triol units are efficiently synthesized by the SnCl4 mediated allylation of chiral α-benzyloxyaldehydes with the uniquely functionalised allylstannane 9. Remarkably, the stereochemistry of t
Cationic BINAP-Ru(II) Halide Complexes: Highly Efficient Catalysts for Stereoselective Asymmetric Hydrogenation of α- and β-Functionalized Ketones
Mashima, Kazushi,Kusano, Koh-hei,Sato, Naomasa,Matsumura, Yoh-ichi,Nozaki, Kyoko,et al.
, p. 3064 - 3076 (2007/10/02)
Cationic ruthenium-BINAP complexes 5, 7, and 10 of the formula Y, where X = Cl, Br, I; Y = Cl, Br, I, BF4, B(C6H5)4; arene = benzene, p-cymene, ethyl benzoate, and their enantiomers have been prepared by the reaction of arene-ruthenium halide complexes 4, 6, and 9 with (S)-BINAP or (R)-BINAP.Structures of the complexes were established by spectroscopy, conductivity, and a single-crystal X-ray analysis (5d: orthorhombic, P21212; a=20.141(2) Angstroem, b=18.504(1) Angstroem, c=12.241(1) Angstroem, V=4562.0(7) Angstroem3, Z=4, R=0.078 for unique 4177 reflections).BINAP derivatives with various substituents at the para and meta positions of four phenyl rings on phosphorus atoms and their cationic Ru(II) complexes have also been synthesized.These BINAP-Ru(II) complexes have been used as catalysts for the asymmetric hydrogenation of various unsaturated organic compounds such as α- and β-keto esters, allylic alcohols, and α,β-unsaturated carboxylic acids in excellent diastereo- and/or enantioselectivities.Catalytic activities and stereoselectivities depend highly on reaction conditions such as solvent, temperature, and additives.Variation of halogen ligands bound to ruthenium atom and substituents on four phenyl rings of BINAP also have exerted remarkable effects on the efficiency of the catalysis.Asymmetric hydrogenation of methyl (+/-)-2-(benzamidomethyl)-3-oxobutanoate catalyzed by the species derived from 9c and 3,5-(t-Bu)2-BINAP afforded the corresponding syn-(2S,3R)-17 in 98percent de and 99percent ee.
STEREOSELECTIVE REDUCTION OF C=X BY A CHIRAL 1,4-DIHYDROPYRIDINE (NADH-MIMIC) IN A SELF-IMMOLATIVE PROCESS
Meyers, A. I.,Brown, Jack D.
, p. 5617 - 5620 (2007/10/02)
A series of prochiral ketones and a prochiral imine was reduced with high absolute stereoselectivity using an optically active 4-methyl-1,4-dihydropyridine in the presence of Mg(ClO4)2.
ASYMMETRIC REACTIONS BASED ON 1,3-OXATHIANES-3. SECONDARY α-HYDROXYACIDS, RCHOHCO2H AND GLYCOLS RCHOHCH2OH
Ko, Kwang-Youn,Frazee, William J.,Eliel, Ernest L.
, p. 1333 - 1344 (2007/10/02)
Reduction of the previously prepared chiral 2-acyl-1,3-oxathianes derived from (+)-pulegone with various metal hydride combinations proceeds stereoselectively, with diastereomer excess (d.e.) of as much as 97percent in the case of reduction of phenyl ketons with lithium tri-sec. butylborohydride.Lesser selectivity (maximum 82percent d.e.) is achived with primary or tertiary alkyl ketones: the predominant diastereomer is readily purified by chromatography.The major product in these cases is that predicted by Cram's chelate rule.The product ratio is reversed with diisobutylaluminium hydride and also in the reduction of secondary alkyl ketones with lithium sec. butylborohydride, where stereoselectivity is low.The 2-hydroxyalkyl-1,3-oxathines are cleaved to α-hydroxyaldehydes with N-chlorosuccinimide-silver nitrate and the aldehydes reduced to glycols, RCHOHCH2OH with sodium borohydride with little or no racemization.Esters, RCHOHCO2CH3, are obtained in high enantiomeric purity by O-benzylating the 2-hydroxyalkyl-1,3-oxathianes prior to cleavage, oxidizing with sodium chlorite following cleavage, esterifying and debenzylating.A method for measuring the enantiomeric purity of glycols RCHOHCH2OH by conversion to 2-phenyl-1,3-dioxolanes with benzaldehyde, followed by proton NMR analysis of the resulting 2-phenyl-4-alkyl-1,3-dioxolane diastereomer pair in the presence of a chiral europium shift reagent is described.
