diastereoselective radical 1,5 phenylmigration reactions fromsilicon in diarylsilyl ethers to various C-centered radicals to form the corresponding 3-phenylated alcohols are described. Functionalized aryl groups can also be transferred. The effect of the variation of the attacking radical on the aryl transfer reaction is discussed. Best results are obtained for the phenylmigration to nucleophilic secondary
Aldehyde-Catalyzed Transition Metal-Free Dehydrative β<i>-</i>Alkylation of Methyl Carbinols with Alcohols
作者:Qing Xu、Jianhui Chen、Quan Liu
DOI:10.1002/adsc.201200996
日期:2013.3.11
borrowing hydrogen strategy in which alcohols were activated by transition metal‐catalyzed anaerobic dehydrogenation, the direct addition of aldehydes was found to be an effective but simpler way of alcohol activation that can lead to efficient and green aldehyde‐catalyzed transition metal‐free dehydrative C‐alkylation of methyl carbinols with alcohols. Mechanistic studies revealed that the reaction proceeds
We developed a chromium-catalyzed, photochemical, and linear-selective alkylation of aldehydes with alkylzirconium species generated in situ from a wide range of alkenes and Schwartz’s reagent. Photochemical homolysis of the C–Zr bond afforded alkyl radicals, which were then trapped by a chromium complex catalyst to generate the alkylchromium(III) species for polar addition to aldehydes. The reaction
for two incompatible enantioselective transformations: a rhodium–diene complex-catalyzed asymmetric 1,4-addition occurs in the hydrophilic corona, while a Rh-TsDPEN-catalyzed asymmetric transfer hydrogenation proceeds in the hydrophobic core. Control experiments and kinetic studies showed that the gated behavior induced by the phototriggered reversible spiropyran to merocyanine transition in the cross-linking
Palladium-catalysed transfer hydrogenation of aromatic nitro compounds — an unusual chain elongation
作者:János Németh、Árpád Kiss、Zoltán Hell
DOI:10.1016/j.tetlet.2013.08.123
日期:2013.11
Aromaticnitrocompounds are reduced via transfer hydrogenation in the presence of palladium on magnesium-lanthanum mixed oxide support in ethanol yielding the corresponding amines. With several acetophenone derivatives, the reduction was accompanied by chain elongation whilst the carbonyl group remained intact.