Preparation of enantiomerically pure trans- and cis-2-(1-naphthyl)cyclohexan-1-ols
摘要:
Lipase-mediated treatment of racemic trans-2-(1-naphthyl)cyclohexan-1-ol with vinyl acetate allows clear-cut enantiospecific kinetic acetylation to give (+)-(1R,2S)-acetate in excellent chemical and enantiomeric excesses leaving (+)-(1S,2R)-alcohol in an excellent enantiomeric purity and excellent recovery. The enantiomerically pure alcohol obtained is transformed into the diastereomeric alcohol neatly via the Mitsunobu inversion reaction.
BF3 can be used in combination with organolithium/strong Lewis base complexes for the enantioselective nucleophilic ring-opening or the carbenoidic rearrangement of various meso-oxiranes with excellent yields and ee values of up to 87 %. Mechanistic aspects of these reactions are considered.
Aryl lithium reagents, complexed with (-)-sparteine, react enantioselectively with cyclic meso epoxides, to afford chiral aryl cyclanols. The enantiomeric excess, though moderate (27-87%), is the best in the literature for such a reaction. Activation by BF3 · OEt2 is needed, and is compatible with a diamine such as (-)-sparteine.
Palladium-catalyzed asymmetric hydrogenation of 2-aryl cyclic ketones for the synthesis of <i>trans</i> cycloalkanols through dynamic kinetic resolution under acidic conditions
The first efficient palladium-catalyzed asymmetric hydrogenation of 2-aryl cyclic ketones has been described through dynamickineticresolution under acidic conditions, providing a facile access to chiral trans cycloalkanol derivatives with excellent enantioselectivities.
Diastereoselective and Enantioselective Silylation of 2-Arylcyclohexanols
作者:Li Wang、Ravish K. Akhani、Sheryl L. Wiskur
DOI:10.1021/acs.orglett.5b00919
日期:2015.5.15
The silylation-based kinetic resolution of trans 2-arylcyclohexanols was accomplished by employing a triaryl silyl chloride as the derivatizing reagent with a commercially available isothiourea catalyst. The methodology is selective for the trans diastereomer over the cis, which provides an opportunity to selectively derivatize one stereoisomer out of a mixture of four. By employing this technology, a facile, convenient method to form a highly enantiomerically enriched silylated alcohol was accomplished through a one-pot reduction-silylation sequence that started with a 2-aryl-substituted ketone.