zinc bromides and regioconvergent Negishi coupling with aryl or alkenyl triflates. The use of a suitable phosphine ligand favoring Pd migration enabled the selective formation of the linear cross‐coupling product. Subsequently, mixtures of secondary alkyl bromides were prepared from linear alkanes by standard bromination, and regioconvergent cross‐coupling then provided access to the corresponding linear
<i>p</i>-Toluenesulfonic Acid Adsorbed on Silica Gel: An Efficient Dehydrating Agent of Alcohols
作者:Franco D'Onofrio、Arrigo Scettri
DOI:10.1055/s-1985-31463
日期:——
Secondary and tertiary alcohols are efficiently dehydrated by reaction with p-toluenesulfonic acid supported on silica gel. In particular, the procedure allows the direct conversion of 3-hydroxy-steroids into Î2-olefins or Î3,5-dienes, without passing through the mesylate or tosylate esters.
Aliphatic Friedel-Crafts reactions. Part VI. Preparation of βγ-unsaturated ketones by the acetylation of substituted cyclohexenes
作者:J. K. Groves、N. Jones
DOI:10.1039/j39680002215
日期:——
Reaction of 1-alkylcyclohexenes with zinc chloride–acetic anhydride produces 6-acetyl-1-alkylcyclohexenes in good yields, together with small amounts of the isomeric 1-acetyl-2-alkylidenecyclohexanes. Hydrogenation of of the unstaurated ketones readily affords 1-acetyl-2-alkylcyclohexanes.
β- and γ-Disubstituted Olefins: Substrates for Copper-Catalyzed Asymmetric Allylic Substitution
作者:Caroline A. Falciola、Karine Tissot-Croset、Hugo Reyneri、Alexandre Alexakis
DOI:10.1002/adsc.200800086
日期:2008.5.5
The copper-catalyzed asymmetric allylic alkylation has shown through many examples that it is a powerful means to generate stereogenic centers with mono β- and γ-substituted olefinic substrates. However, little has been reported about more substituted olefinic patterns, such as β-disubstituted allylic electrophiles. In this paper, we show that a simple procedure using easily accessible Grignard reagents