21777-18-4Relevant articles and documents
γ-Regioselective Functionalization of 3-Alkenylindoles via 1,6-Addition to Extended Alkylideneindolenine Intermediates
Bertuzzi, Giulio,Lenti, Lucia,Giorgiana Bisag, Denisa,Fochi, Mariafrancesca,Petrini, Marino,Bernardi, Luca
supporting information, p. 1296 - 1302 (2018/02/28)
Alkylideneindolenines are widely employed key electrophilic intermediates for the α-functionalization of the C-3 side chain of indoles. However, the reactivity of their extended (vinylogous) counterparts has not been carefully explored so far. These intermediates can undergo 1,4- or 1,6-addition with functionalization at α- or γ-position of the side chain, resulting in regioisomeric mixtures of products. This work demonstrates that a complete γ-regioselectivity can be achieved in the reaction of 3-indol-3-yl allylic alcohols with various nucleophiles. This process is catalysed by just 1 mol% zinc(II) triflate at room temperature and entails the 1,6-selective addition of the nucleophile to an extended protonated alkylideneindolenine generated in situ. Indoles, pyrroles, anilines and thiols can be efficiently used as nucleophilic partners for this reaction, delivering the corresponding 3-vinyl substituted, γ-functionalised indole products in moderate to good yields. (Figure presented.).
L-Proline-catalyzed Knoevenagel condensation: A facile, green synthesis of (E)-ethyl 2-cyano-3-(1H-indol-3-yl)acrylates and (E)-3-(1H-indol-3-yl) acrylonitriles
Venkatanarayana,Dubey
experimental part, p. 1746 - 1759 (2012/05/04)
L-Proline has been utilized as a novel and ecofriendly catalyst in ethanol medium for the Knoevenagel condensation of indole-3-carboxyaldehydes and their N-methyl derivatives 1(a-e) and 4(a-e) with the active methylene compound, ethyl cyanoacetate (2) to afford substituted (E)-ethyl 2-cyano-3-(1H-indol-3-yl) acrylates 3(a-e) and 5(a-e) respectively. These products were reacted with dimethyl sulfate in the presence of PEG-600 as an efficient and green solvent to afford the corresponding N-mthylated derivatives 5(a-e). These Knoevenagel products react with 5% NaOH, yielding (E)-3-(1H-indol-3-yl)acrylonitriles 6(a-e) and 7(a-e). Copyright Taylor & Francis Group, LLC.
Borrowing hydrogen: Indirect "Wittig" olefination for the formation of C-C bonds from alcohols
Black, Phillip J.,Edwards, Michael G.,Williams, Jonathan M. J.
, p. 4367 - 4378 (2007/10/03)
The successful development of an indirect three-step domino sequence for the formation of C-C bonds from alcohol substrates is described. An iridium-catalysed dehydrogenation of alcohol 1 affords the intermediate aldehyde 2. The desired C-C bond can then be formed by a facile Wittig olefination, yielding the intermediate alkene 3. In the final step the alkene is hydrogenated to afford the indirect Wittig product, the alkane 4. The key to this process is the concept of borrowing hydrogen; hydrogen removed in the initial dehydrogenation step is simply borrowed by the iridium catalyst. Functioning as a hydrogen reservoir, the catalyst facilitates C-C bond formation before subsequently returning the borrowed hydrogen in the final step. Herein we present full details of our examination into both the substrate and reaction scope and the limitations of the catalytic cycle. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
