Non-destructive Removal of the Bornanesultam Auxiliary in ?-SubstitutedN-Acylbornane-10,2-sultanis under Mild Conditions: An efficient synthesis of enantiomerically pure ketones and aldehydes
作者:Wolfgang Oppolzer、Christophe Darcel、Patrick Rochet、Stephane Rosset、Jef De Brabander
DOI:10.1002/hlca.19970800502
日期:1997.8.11
two-step procedure involving a known mercaptolysis reaction followed by an [Fe(acac)3]-mediated coupling of the resulting S-benzyl thioesters with Grignard reagents. Furthermore, enantiomerically pure aldehydes 23 can be obtained from α-substituted N-acylbornane-10,2-sultams 6via a one-step reduction with (i-Bu)2AIH. No epimerization at the α-chiral center is observed during the cleavage reaction whereby
Rearrangement of <i>N</i>-<i>tert</i>-Butanesulfinyl Enamines for Synthesis of Enantioenriched α-Hydroxy Ketone Derivatives
作者:Chun-Tian Li、Hui Liu、Yun Yao、Chong-Dao Lu
DOI:10.1021/acs.orglett.9b03159
日期:2019.10.18
hexamethyldisilazide (or potassium tert-butoxide) and methyl triflate gives N-methylated N-tert-butanesulfinyl enamine intermediates that undergo stereoselective [2,3]-rearrangement to afford α-sulfenyloxy ketones with excellent enantiopurities. This cascade of enamination-N-methylation-rearrangement was even used to generate acyclic tertiary α-hydroxy ketones bearing two α-substituents showing negligible
Chiral Brønsted Acid from a Cationic Gold(I) Complex: Catalytic Enantioselective Protonation of Silyl Enol Ethers of Ketones
作者:Cheol Hong Cheon、Osamu Kanno、F. Dean Toste
DOI:10.1021/ja204331w
日期:2011.8.31
developed from a cationic gold(I) disphosphine complex in the presence of alcoholic solvent and applied to the enantioselective protonation reaction of silylenolethers of ketones. Various optically active cyclic ketones were obtained in excellent yields and high enantioselectivities, including cyclic ketones bearing aliphatic substrates at the α-position. Furthermore, the application of this Brønsted acid
thyl)sulfoximines and carbonyl compounds by an addition-elimination-isomerization reaction sequence. Under basic conditions, complete isomerization of the vinylic sulfoximines, obtained as intermediates, to the corresponding allylicsulfoximines takes place. Chromatographically separable mixtures of (E) and (Z) allylicsulfoximines were isolated in the case of beta,gamma-disubstituted allylic sulfoximines
The potential of Song’s chiral oligoethylene glycols (oligoEGs) as catalysts was explored in the enantioselective protonation of trimethylsilyl enolethers in combination with alkali metal fluoride (KF and CsF) and in the presence of a proton source. Highly enantioselective protonations of various silylenolethers of α-substituted tetralones were achieved, producing chiral α-substituted tetralones