- Knoevenagel-Doebner condensation promoted by chitosan as a reusable solid base catalyst
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The development of green and sustainable processes using naturally occurring biopolymers is becoming one of the suitable remedies to replace the conventional catalytic systems that generate large amount of byproducts with high risk factors. In this context, although Knoevenagel-Doebner condensation reaction has been reported with many organocatalysts including proline, no attempts were made to develop heterogeneous catalysts with environmental concerns. Considering these factors in mind, the title reaction is studied with chitosan as a heterogeneous solid base catalyst for the synthesis of α,β-unsaturated carboxylic acids through the condensation followed by decarboxylation reactions. Chitosan offers many advantages including high stability as evidenced by leaching, reusability tests, wide substrate scope and providing higher yields of the desired products with high purity. Powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscope (SEM) and elemental analysis revealed that there are no major changes in the structural integrity and morphology of chitosan before and after catalysis under the optimized reaction conditions.
- Anbu, Nagaraj,Hariharan, Surendran,Dhakshinamoorthy, Amarajothi
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- The studies on the chemoenzymatic synthesis of 2-benzyl-3-butenoic acid
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The studies on the chemoenzymatic synthesis of 2-benzyl-3-butenoic acid 3 were performed. The alkylation of dienolates derived from the crotonic and vinylacetic acids with different types of alkylating agents was examined. In all cases the inseparable mixture of isomeric acids 3 and 4 were obtained. Chemoselective enzymatic esterification of those mixtures provides ester 6 in 86% yield as a single product without double bond isomerization. None common method can be used for its hydrolysis since under basic conditions only isomeric acid 5 is formed. To overcome this limitation enzyme catalysed hydrolysis process was design. This protocol afforded isomerically pure acid 3 in 98% yield.
- Borys, Filip,Paprocki, Daniel,Koszelewski, Dominik,Ostaszewski, Ryszard
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- Design, synthesis and biological evaluation of benzothiazepinones (BTZs) as novel non-ATP competitive inhibitors of glycogen synthase kinase-3β (GSK-3β)
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Glycogen synthase kinase-3β (GSK-3β) plays a key role in type II diabetes and Alzheimer's diseases, to which non-ATP competitive inhibitors represent an effectively therapeutical approach due to their good specificity. Herein, a series of small molecules benzothiazepinones (BTZs) as novel non-ATP competitive inhibitors of GSK-3β have been designed and synthesized. The in vitro evaluation performed by luminescent assay showed most BTZ derivatives have inhibitory effects in micromolar scale. Among them compounds 6l, 6t and 6v have the IC50 values of 25.0 μM, 27.8 μM and 23.0 μM, respectively. Moreover 6v is devoid of any inhibitory activity in the assays to other thirteen protein kinases. Besides, SAR is analyzed and a hypothetical enzymatic binding mode is proposed by molecular docking study, which would be useful for new candidates design.
- Zhang, Peng,Hu, Hai-Rong,Bian, Shi-Hui,Huang, Zhao-Hui,Chu, Yong,Ye, De-Yong
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- Method for regio- and stereoselective synthesis of (E)-Β,γ- unsaturated acids from aldehydes under solvent-free conditions
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Synthesis of (E)-β,-γunsaturated acids from aldehydes with malonic acid has been explored under solvent-free conditions. The modified Knoevenagel condensation reaction with N-methyl morpholine (NMM) as catalyst exhibits highly β,-γ regioselectivity and exclusively E-stereoselectivity. A mechanism accounting for both regio- and stereoselectivity has been proposed and preliminarily studied. Copyright Taylor & Francis Group, LLC.
- Zhang, Shi-Jie,Hu, Wei-Xiao
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experimental part
p. 3093 - 3100
(2010/12/19)
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- Selective oxidation of aromatic primary alcohols to aldehydes using molybdenum acetylide oxo-peroxo complex as catalyst
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Selective oxidation of various aromatic alcohols to aldehydes has been carried out with very high conversion (90%) and selectivity (90%) for aldehydes using cyclopentadienyl molybdenum acetylide complex, CpMo(CO)3(C{triple bond, long}CPh) (1) as catalyst and hydrogen peroxide as environmentally benign oxidant. Water-soluble Mo acetylide oxo-peroxo species is formed in situ after reaction of 1 with aqueous hydrogen peroxide during the course of reaction as catalytically active species. Interestingly even though the catalyst is homogeneous it could be recycled very easily by separating the products in organic phase and catalyst in aqueous phase using separating funnel. Even after five recycles no appreciable loss in alcohol conversion and aldehyde selectivity was observed.
- Biradar, Ankush V.,Dongare, Mohan K.,Umbarkar, Shubhangi B.
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experimental part
p. 2885 - 2888
(2009/09/06)
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- Carbonyl homologation via α-trimethylsilyl β-lactone rearrangements. A nonbasic alternative to the Wittig reaction
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Saturated and unsaturated aldehydes and ketones, when treated with trimethylsilylketene and BF3 for 16 hours, form β-lactones which spontaneously rearrange to α,β-unsaturated TMS esters; these hydrolyze during workup to form the corresponding carboxylic acids.
- Black,Zhang,Huang,Smith,Yates
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