Ynolates were found to react with alpha-alkoxy-, alpha-siloxy-, and alpha-aryloxyketones at room temperature to afford tetrasubstituted olefins with high Z selectivity. Since the geometrical selectivity was determined in the ring opening of the beta-lactone enolate intermediates, the torquoselectivity was controlled by the ethereal oxygen atoms. From experimental and theoretical studies, the high Z
New Methylene Homologation Method for Cyclic Ketones
作者:Huaqing Liu、Chunrui Sun、Nam-Kyu Lee、Roger F. Henry、Daesung Lee
DOI:10.1002/chem.201201346
日期:2012.9.17
Teaching new tricks to an old dog: By intercepting adducts between ketones and lithium trimethylsilyldiazomethane, a new Tiffeneau–Demjanov type methylenehomologation could be realized in a single‐step operation. Among proton sources and Lewis acids, silica gel was found to be the most effective reagent for the protonation of intermediates and their subsequent ring expansion (see scheme).
Lewis Acid Promoted Carbon−Carbon Bond Cleavage of γ-Silyloxy-β-hydroxy-α-diazoesters
作者:Cristian Draghici、Matthias Brewer
DOI:10.1021/ja801004d
日期:2008.3.1
Cyclic gamma-silyloxy-beta-hydroxy-alpha-diazoesters undergo efficient rupture of the Cbeta-Cgamma bond when treated with tin tetrachloride to provide tethered aldehyde ynoate products in high yield.
Preparation of Tethered Aldehyde Ynoates and Ynones by Ring Fragmentation of Cyclic γ-Oxy-β-hydroxy-α-diazo Carbonyls
作者:Ali Bayir、Cristian Draghici、Matthias Brewer
DOI:10.1021/jo902405f
日期:2010.1.15
Cyclic gamma-oxy-beta-hydroxy-alpha-diazo carbonyls undergo Lewis acid induced ring fragmentation to provide either ynoates or ynones tethered to an aldehyde, ketone, or ester. The fragmentation precursors are convenient to prepare by adding lithiated alpha-diazo carbonyls to alpha-oxy ketones. The fragmentation appears general and provides a variety of functional group-rich products in good to excellent yield.
Thermodynamic and kinetic control in the reaction of carboethoxymethylene- triphenylphosphorane and ethyl lithiotrimethylsilylacetate with 2- (t-butyldimethylsilyloxy)cycloalkanones.
作者:Gerald L. Larson、J.Antonio Prieto、Antonio Hernandez