Diastereoselective Oxidative Carbon−Carbon Bond Formation via Silyl Bis-enol Ethers
作者:Christopher T. Avetta、Leah C. Konkol、Carla N. Taylor、Karen C. Dugan、Charlotte L. Stern、Regan J. Thomson
DOI:10.1021/ol802516z
日期:2008.12.18
Diisopropylsilyl bis-enol ethers are shown to be powerful intermediates for the diastereoselective dimerization and cross-coupling of cyclic ketones. The trends observed for the oxidative coupling of a range of different dialkylsilyl bis-enol ethers derived from cyclohexanone are rationalized by invoking a stereochemical model based on a Thorpe-Ingold effect.
General and Efficient α-Oxygenation of Carbonyl Compounds by TEMPO Induced by Single-Electron-Transfer Oxidation of Their Enolates
作者:Emanuela Dinca、Philip Hartmann、Jakub Smrček、Ina Dix、Peter G. Jones、Ullrich Jahn
DOI:10.1002/ejoc.201200736
日期:2012.8
for the synthesis of protected α-oxygenated carbonylcompounds is reported. It is based on the single-electron-transfer oxidation of easily generated enolates to the corresponding α-carbonyl radicals. Coupling with the stable free radical TEMPO provides α-(piperidinyloxy) ketones, esters, amides, acids or nitriles in moderate-to-excellent yields. Enolate aggregates influence the outcome of the oxygenation
Diastereo- and Enantioselective Synthesis of<i>syn</i>-2,3-Disubstituted 1,4-Diketones<i>via</i>Oxidative Coupling of Metalated Hydrazones
作者:Dieter Enders、Peter Müller、Daniela Klein
DOI:10.1055/s-1998-1562
日期:1998.1
An efficient diastereo- and enantioselective synthesis of syn-2,3-disubstituted 1,4-diketones 4 is described. Key step of the procedure is the oxidative coupling of the metalated SAMP/RAMP-hydrazones 2 with iodine, followed by oxidative cleavage of the dimerized bishydrazones 3 with ozone and subsequent separation of the minor meso-isomer by chromatography. The d,l-isomers of the title 1,4-diketones 4 are obtained in good overall yields (20-64%) and high diastereo- and enantiomeric excesses (de ≥ 98%, ee = 80- ≥ 95%).
Intermolecular [4 + 2]-Cycloadditions of Nitroalkenes with Cyclic Olefins. Transformations of Cyclic Nitronates
作者:Scott E. Denmark、Christopher J. Cramer、Jeffrey A. Sternberg
DOI:10.1002/hlca.19860690823
日期:1986.12.10
Nitrocyclohexene undergoes facile SnCl4-induced, [4 + 2]-cycloadditions with simple cycloalkenes to produce nitronates. The nitronates can be transformed sterospecifically into a number of other functional groups (alcohol, ketone, oxime, amine) by hydrolytic, reductive, and oxidative processes. The mechanism of the [4 + 2]-cycloaddition is believed to involve formation of a zwitterionic intermediate