نتایج جستجو برای: claisen rearrangement
تعداد نتایج: 27614 فیلتر نتایج به سال:
Arylsulfinyl groups direct the metal-free, regiospecific, nucleophilic ortho-allylation of pyrroles and pyrazoles. Mechanistic studies support the intermediacy of allylsulfonium salts that undergo facile thio-Claisen rearrangement onto the heterocyclic ring, giving products of coupling. The strategy has been adapted to allow regiospecific propargylation of the heterocyclic substrates.
A novel and efficient approach to 3-allyl-chromones from alkynones and allylic alcohols via a tandem Michael addition-Claisen rearrangement-O-arylation reaction has been developed. Diversely structural 3-allyl-chromones were afforded in up to 93% yield for 24 examples. This synthetic strategy is regiospecific, highly efficient, environment friendly and metal-free.
The Johnson-Claisen rearrangement of D-gluco and L-ido-derived allylic orthoesters afforded gamma,delta-unsaturated ester that on ester reduction, epoxidation, regioselective oxirane opening by sodium azide and hydrogenation led to sugar amino alcohols--immediate precursors for 1-deoxy-homonojirimycin 3a,b, and polyhydroxylated homoazepanes 4a,b. Our synthetic approach and glycosidase inhibitor...
Attempted RCM of 2,2'-bis(allyloxy)-1,1'-binaphthyl resulted in a Claisen-type rearrangement of a postulated labile dioxacyclodecine proceeding at room temperature and followed by [2+2] cycloaddition. Structures of products were confirmed by X-ray crystallography. A mechanistic rationalisation based on relative stabilities of proposed intermediates and transition states is provided.
γ-aminobutiric acid (gaba), the major inhibitory neurotransmitter in the central nervous system is activated by the antispastic and muscle relaxant agent, baclofen, which is a lipophilic derivative of gaba. because of its biological and pharmacological importance, there are several reports in the literature about the synthesis of baclofen since 1962. in this study baclofen was easily synthesize...
We have previously clarified that the strongly electron-withdrawing CF3 group nicely affected base-mediated proton shift of CF3-containing propargylic or allylic alcohols to afford corresponding α,β-unsaturated saturated ketones, respectively, which was applied this time Claisen rearrangement after O-allylation with a group, followed by isomerization allyl vinyl ethers via shift, enabling desir...
The title compound, C(16)H(18)F(6)O(4), was obtained through an unprecedented one-pot reaction sequence involving a Gosteli-Claisen rearrangement and a cyclo-isomerization. The constitution and relative configuration were determined by single-crystal X-ray diffraction analysis. In the crystal, mol-ecules are connected via O-H ⋯ O hydrogen bonds.
A series of ynenyl allyl ethers were rearranged into polysubstituted furans in the presence of a gold(I) catalyst. It is proposed that the transformation involves a Claisen-type rearrangement that allows the efficient creation of quaternary centers under mild experimental conditions.
[figure: see text] A tandem anionic 5-exo-dig cyclization/Claisen rearrangement sequence was used to effect a facile, "one-pot" conversion of an appropriately substituted 4-alkyn-1-ol to the tetracyclic carbon core structure of phorbol. The synthesis was conducted using readily available nonracemic starting materials to provide the target structure as a single enantiomer in high chemical yield.
Synthesis of substituted 1,3-dienes was achieved via gold(I)-catalyzed Claisen rearrangement of allenyl vinyl ethers. The N-heterocyclic carbene gold chloride catalyst (IPrAuCl) was superior in terms of activity and selectivity and afforded the 3,3-product in excellent yields. A proposed cation-π inter-action played a significant role in affecting the reaction rate.
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