472 research outputs found
Polyoxometalate-intercalated layered double hydroxides as efficient and recyclable bi-functional catalysts for cascade reactions
The polyoxometalate (POM) intercalated-layered double hydroxides (LDHs) have been widely used as heterogeneous catalysts. However, the application of POM-LDHs as bi-functional catalysts for cascade reaction has seldom been studied comparing with the noble metal-based catalysts. Herein, a series of POM-LDHs catalysts of Tris-LDH-X4(PW9)2 (X = Mn, Fe, Co, Ni, Cu and Zn) has been prepared; The efficacy of Tris-LDH-Zn4(PW9)2 as efficient bi-functional catalyst has been demonstrated for cascade reactions involving oxidation of benzyl alcohol to benzaldehyde followed by Knoevenagel condensation with ethyl cyanoacetate to produce benzylidene ethyl cyanoacetate. The combination of POM's redox/acidic sites and LDHs's basic sites led to a composite catalyst with excellent activity (99%) and selectivity (≥ 99%) under mild and soluble-base-free conditions. This work offer a new design strategy for the fabrication of efficient bi-functional catalysts for the promotion of one-pot cascade reactions
8H-Chromeno[2′,3′:4,5]imidazo[2,1-a]isoquinoline
The title compound, C18H12N2O, comprises two aromatic fragments, viz., imidazo[2,1-a]isoquinoline and benzene, linked by oxygen and methylene bridges. Despite the absence of a common conjugative system within the molecule, it adopts an essentially planar conformation with an r.m.s. deviation of 0. 036 Å. In the crystal, due to this structure, molecules form stacks along the b axis by π⋯π stacking interactions, with shortest C⋯C distances in the range 3.340 (4)–3.510 (4) Å. The molecules are bound by intermolecular C—H⋯O interactions within the stacks and C—H⋯π interactions between the stacks
Synthesis of diverse indole-containing scaffolds by gold(I)-catalyzed tandem reactions of 3-propargylindoles initiated by 1,2-indole migrations: scope and computational studies
Similar to propargylic
carboxylates and sulphides, 3-
propargylindoles undergo 1,2-indole
migrations under cationic gold(I)-
catalysis. The intermediate Aucarbenoid
complex may evolve through
different pathways depending on the
substituents at the propargylic and
terminal positions of the alkyne moiety.
Thus, 3-indenylindole derivatives were
easily obtained through formal iso-
Nazarov or Nazarov cyclizations. DFT
computations support the formation of
an alkylidenecyclopropane intermediate
that undergoes aura-iso-Nazarov or
aura-Nazarov cyclizations upon
torquoselective ring opening. In
addition, 3-dienylindoles could be
accessed when none of the referred
pathways were accessible and so the
intermediate Au-carbenoid complex
evolved via a 1,2-CH insertion
reaction. We have also demonstrated
that the final products can be obtained
in a one-pot protocol from easily
available propargylic alcohols and
indolesMEC/FEDER (CTQ2007-61436/BQU) and Junta de Castilla y León (BU021A09) for financial support. We are also grateful to MEC (FPU predoctoral fellowship to D.M., “Young Foreign Researchers” contract (SB2006-0215) to M.G., “Ramón y Cajal” contract to M.A.F.-R., and “Juan de la Cierva” contract to P.G.-G.) and Fundación Ramón Areces (predoctoral fellowship to A.G.P.).This is the peer reviewed version of the following article: Sanz, R., Miguel, D., Gohain, M., García-García, P., Fernández-Rodríguez, Manuel A., González-Pérez, A., Nieto-Faza, O., de Lera, Ángel R. and Rodríguez, F. (2010), Synthesis of Diverse Indole-Containing Scaffolds by Gold(I)-Catalyzed Tandem Reactions of 3-Propargylindoles Initiated by 1,2-Indole Migrations: Scope and Computational Studies. Chem. Eur. J., 16: 9818–9828. doi:10.1002/chem.201001162, which has been published in final form at doi:10.1002/chem.201001162. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archivin
Tandem synthesis of alternating polyesters from renewable resources
The vast majority of commodity materials are obtained from petrochemical feedstocks. These resources will plausibly be depleted within the next 100 years, and the peak in global oil production is estimated to occur within the next few decades. In this regard, biomass represents an abundant carbon-neutral renewable resource for the production of polymers. Here we report a new strategy, based on tandem catalysis, to obtain renewable materials. Commercially available complexes are found to be efficient catalysts for alternating polyesters from the cyclization of dicarboxylic acids followed by alternating copolymerization of the resulting anhydrides with epoxides. This operationally simple method is an attractive strategy for the production of new biodegradable polyesters
Homogeneous and heterogeneous catalysts for multicomponent reactions
[EN] Organic synthesis performed through multicomponent reactions is an attractive area of research in
organic chemistry. Multicomponent reactions involve more than two starting reagents that couple in an
exclusive ordered mode under the same reaction conditions to form a single product which contains the
essential parts of the starting materials. Multicomponent reactions are powerful tools in modern drug
discovery processes, because they are an important source of molecular diversity, allowing rapid,
automated and high throughput generation of organic compounds. This review aims to illustrate
progress in a large variety of catalyzed multicomponent reactions performed with acid, base and metal
heterogeneous and homogeneous catalysts. Within each type of multicomponent approach, relevant
products that can be obtained and their interest for industrial applications are presented.The authors wish to gratefully acknowledge the Generalitat Valenciana for the financial support in the project CONSOLIDER-INGENIO 2010 (CSD2009-00050)Climent Olmedo, MJ.; Corma Canós, A.; Iborra Chornet, S. (2012). Homogeneous and heterogeneous catalysts for multicomponent reactions. RSC Advances. 2(1):16-58. https://doi.org/10.1039/c1ra00807bS16582
Organocatalytic asymmetric domino Michael–Henry reaction for the synthesis of substituted bicyclo[3.2.1]octan-2-ones
This paper was submitted for publication in the journal "Chemical Communications" and the definitive version can be found at: http://dx.doi.org/10.1039/c3cc39165eThe first organocatalytic asymmetric reaction between 1,4-cyclohexanedione and nitroalkenes have been studied, affording bicyclo[3.2.1]octane derivatives containing four continuous stereogenic centres. The products were obtained through a domino Michael-Henry process as a single diastereoisomer with excellent enantioselectivities
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