Dibenzyl Malonate Research Articles

Stereoselective mechanochemical synthesis of thiomalonate Michael adducts via iminium catalysis by chiral primary amines.

The study presents a novel approach utilizing iminium salt activation and mild enolization of thioesters, offering an efficient and rapid synthesis of Michael adducts with promising stereoselectivity and marking a significant advancement in mechanocatalysis. The stereoselective addition of bisthiomalonates 1-4 to cyclic enones and 4-chlorobenzylideneacetone proceeds stereoselectively under iminium activation conditions secured by chiral primary amines, in contrast to oxo-esters as observed in dibenzyl malonate addition. Mild enolization of thioesters allows for the generation of Michael adducts with good yields and stereoselectivities. Reactions in a ball mill afford product formation with similar efficacy to solution-phase reactions but with slightly reduced enantioselectivity, yet they yield products in just one hour compared to 24 or even 168 hours in solution-based reactions. It is noteworthy that this represents one of the early reports on the application of iminium catalysis using first-generation chiral amines under mechanochemical conditions, along with the utilization of easily enolizable thioesters as nucleophiles in this transformation.

Mechanochemical Assisted Chemoselective and Stereoselective Hydrogen‐Bonding Catalyzed Addition of Dithiomalonates to Enones

AbstractDithiomalonates proved to be active nucleophiles in the stereoselective additions to chalcones, dienones, and en‐ynones affording the desired Michael adducts with moderate to good yield and enantioselectivities up to 98%. In contrast, the analogous dibenzyl malonate remained inactive. Bifunctional Cinchona squaramides secured the effective chirality transfer and the selectivity towards Michael adducts of various bisthiomalonates following the soft enolization approach. The thioester's nature impacted the reactivity and stability of the reactants or products. The reactions performed in solution led to the product, but it required prolonged time along with byproducts formation such as sulfa‐Michael adducts, thus limiting the applicability of more reactive dithioesters. On the contrary, the reactions performed under solvent‐free, ball milling conditions furnished adducts in substantially less time, with negligible or no byproduct generation. Therefore, the mechanochemical approach revealed to be an effective tool for supporting the hardly effective reactions under standard solution conditions. The conducted comprehensive KS‐DFT studies are in line with the experimental observations shedding more light on the intricate active nucleophile formation at a molecular level and different chemical reaction pathways, as well as indicating the crucial transitions state governing the observed stereoselectivities.

Modified Rice Husk Silica from Biowaste: An Efficient Catalyst for Transesterification of Diethyl Malonate and Benzyl Alcohol

Molybdenum and lanthanum oxide modified silica-based catalysts were prepared from the agricultural waste rice husk. These synthesized catalysts were characterized by various spectroscopic and non-spectroscopic techniques. The catalytic performance was investigated by transesterification reaction between diethyl malonate and benzyl alcohol in the liquid phase using modified silica as a heterogeneous catalyst. Molybdenum modified silica-based catalyst showed the highest conversion efficiency of 95.6% and selectivity of 96.8% for dibenzyl malonate. The reaction conditions were optimized to give maximum efficiency with the highest selectivity in a solvent-free green method.

Design of Sulphate Modified Solid Acid Catalysts for Transesterification of Diethyl Malonate with Benzyl Alcohol.

Sulphate ion modified multiwalled carbon nanotubes (S-CNTs), mesoporous carbon (S-MC), zirconia (S-ZrO2), alumina (S-Al2O3) and silica (S-SiO2) were prepared by wet impregnation technique. The physico-chemical properties of the prepared materials were investigated by Powder-XRD, BET-Surface area and SEM-EDS analysis. Surface acidity of the materials was analyzed using TPD-NH3 and n-butyl amine titration methods. Catalytic activity of these materials was investigated in liquid phase transesterification of diethyl malonate with benzyl alcohol. Effect of various reaction parameters on product yield as well as recyclability of the catalysts was investigated. Kinetics of the reactions was studied and activation energy was evaluated. All the catalysts investigated in this reaction were found to be catalytically active except S-Al2O3, for the formation of transester products; benzyl ethyl malonate (BEM) and dibenzyl malonate (DBM). S-ZrO2 and S-MC resulted good % yield (70 and 73% respectively) of total transester products where as S-CNTs showed 100% selectivity towards the formation of only BEM. Acid sites with moderate acid strength are found to be catalytically active for the transesterification reaction. The catalysts were recyclable up to 5 times without significant loss in their catalytic activity except in the case of S-MC. The reaction followed first order kinetics and the energy of activation of the reaction with different catalysts was in the range of 12-58 kJ mol-1.

Lipase-ultrasound assisted synthesis of polyesters

Poly (ethylene glutarate), poly (ethylene malonate) and poly (ethylene phthalate), were enzymatically synthesized by immobilized Candida antarctica lipase B in solvent free conditions. The synthesis of these polyesters was based on the ester-ester exchange reaction between ethylene glycol diacetate and di-ethyl glutarate, di-benzyl malonate, di-n-octyl phthalate to produce poly (ethylene glutarate), poly (ethylene malonate) and poly (ethylene phthalate), respectively. The effect of ultrasound and PET polymeric beads was evaluated and showed to improve the synthesis of all polyesters. Ultrasound, as a green solvent-free technology, showed high potentiality for the polyester synthesis intensification.

Synthesis and Characterisation of Various Diester and Triester Adducts of TiCl4

AbstractTitanium(IV) chloride and the triester glycerol tribenzoate (gtb) were reacted under moisture‐free conditions in order to investigate the use of triester‐containing oils in the purification of TiCl4 in industrial processes. This resulted in the isolation of a chloro‐bridged dimeric complex containing four titanium centres [{(TiCl4)2(gtb)}2] (1). Further novel coordination compounds of TiCl4 and the diesters; diisopropyl malonate, dibenzyl malonate and diethyl succinate were synthesised by direct reaction under moisture‐free conditions, yielding [TiCl4{CH2(COOiPr)2}] (2), [TiCl4{CH2(COOCH2Ph)2}] (3) and [TiCl4{C2H4(COOEt)2}] (4) respectively. The structures of compounds 1–4 were determined by single‐crystal X‐ray diffraction. All structures assumed an octahedral geometry consisting of the titanium bound to four chloride ligands and the diester molecule acting as a bidentate ligand, through its two carbonyl oxygen atoms. Exposure of the isopropyl malonate reaction to trace amounts of water during synthesis resulted in the formation of an oxo‐bridged dimeric structure [Ti2(μ‐O)Cl3{CH2(COOiPr)2}2] (2b), the structure of which was also obtained via single‐crystal X‐ray diffraction.

Improved Synthesis of Cyclic α-Hydrazino Acids of Five- to Nine-Membered Rings and Optical Resolution of 5,6,7-Membered Ring Hydrazino Acids

Synthesis of cyclic α-hydrazino acids of five- to nine-membered rings has been described. Di-tert-butyl or dibenzyl malonate was used as starting materials instead of diethyl malonate, which was used in our first report. Deprotection of tert-butyl or benzyl ester of the final compounds was much easier than that of ethyl or methyl esters. Overall yield of these acids were 39, 50, 47, 52, and 51%, respectively. These acids were then converted to the diastereomers either via the formation of peptides with L-phenylalanine methyl ester or via the formation of esters (for five- to seven-membered rings) with L-2-phenylalaninol. All diastereomers were separated except the nine-membered ring by flash chromatography. Hydrolysis of diastereomeric esters generated the optically pure five-, six- and seven-membered cyclic α-hydrazino acids. In this process, both the enantiomers have been isolated and the chiral auxiliary L-2-phenylalaninol was recovered. Absolute stereochemistry was determined from x-ray crystallographic analysis.

Transesterification of diethyl malonate with benzyl alcohol catalyzed by modified zirconia: Kinetic study

Zirconia and its modified forms such as 10%Mo(VI)/ZrO2, 10%V(V)/ZrO2, 10%W(VI)/ZrO2 and SO42−/ZrO2 were prepared and characterized for their physico-chemical properties such as BET for surface area, NH3-TPD and n-butylamine back titration method for total surface acidity, PXRD technique for crystallinity and ICP-OES technique for elemental analysis. These materials were used as catalysts in liquid phase transesterification reaction of diethyl malonate (DEM) with benzyl alcohol (BA). Optimization of reaction conditions such as reaction time, reaction temperature, weight of the catalyst and molar ratio of reactants were carried out to obtain highest possible transester yield. Dibenzyl malonate (DBM) and benzyl ethyl malonate (BEM) were obtained as major products. Highest total transester yield of (88%) was obtained in the presence of 0.75g of SZ catalyst at a molar ratio of DEM: BA=1:3, reaction temperature of 393K and reaction time 5h. Kinetic studies were carried out to find out the rate of the reaction and energy of activation values for zirconia catalysts, in order to identify a facile catalyst system for this reaction. A possible reaction mechanism was proposed based on the kinetic data and it was observed that Eley-Rideal mechanism fits well for this reaction. Reactivation and reusability studies of the catalysts were also taken up.

ChemInform Abstract: A Heterogeneous Layered Bifunctional Catalyst for the Integration of Aerobic Oxidation and Asymmetric C—C Bond Formation.

AbstractA novel layered heterogeneous bifunctional chiral catalyst consisting of bimetallic alloy nanoparticles and a chiral polymer‐supported Jorgensen—Hayashi‐type organocatalyst (POC) is designed, synthesized and successfully applied to the sequential aerobic oxidation—asymmetric Michael reaction of primary allylic alcohols and dibenzyl malonate.

Highly Efficient Catalytic Enantioselective Mannich Reaction of Malonates with N‐tert‐Butoxycarbonyl Imines by Using Yb(OTf)3/Pybox Catalysts at Room Temperature

Go Mannich! A highly efficient and enantioselective method for the direct asymmetric reaction of dibenzyl malonate with N-tert-butoxycarbonyl aldimines in the presence of Yb(OTf)3 and iPr-pybox complexes is described (see scheme; pybox = pyridine bisoxazoline).

A heterogeneous layered bifunctional catalyst for the integration of aerobic oxidation and asymmetric C–C bond formation

The design and synthesis of a heterogeneous bifunctional chiral catalyst for the sequential aerobic oxidation-asymmetric Michael reactions between primary allylic alcohols and dibenzyl malonate are described. Interestingly, we found that layering bimetallic nanoparticles over the organocatalyst, within the chiral composite material, is crucial for catalytic activity.

One-pot synthesis of poly-substituted tetramic acids for the preparation of putative turn mimics

A one-pot synthesis of poly-substituted tetramic acids and of their six-membered ring analogs have been obtained in one step by reaction of N-Boc dipeptides, activated as their O-succinimidyl esters (Boc-AA-AA-OSu), with the sodium anion of dibenzyl malonate. The adducts spontaneously cyclize to form five or six-member rings. To check whether this class of compounds may be used to promote reverse-turn conformations, one adduct was further derivatized. The formation of a hydrogen bond between the NH–Boc and the carbonyl at C2 of the heterocycle is highlighted, upon analysis of the product by IR, 1H NMR, and MD techniques, thus suggesting that these compounds are good candidates to promote reverse-turn conformations or other secondary structures and may be used for the formation of new foldamers.

Catalytic Asymmetric Protonation of Chiral Calcium Enolates

Asymmetric protonation represents a powerful methodology for constructing tertiary chiral carbon centers, with catalytic versions being of particular importance. However, excellent chiral environments should be designed for these transformations due to the steric nature of the hydrogen atom. In this paper the authors developed a highly enantioselective protocol for the catalytic asymmetric protonation of chiral calcium enolates, which were prepared in situ from amides 1 and dibenzyl malonate via 1,4-addition. 10 mol% of Ca(OEt)2, 10 mol% of phenol 2, and 11 mol% of Ph-PyBox 3 constituted the optimum system. ­Excellent yields (72-96%) and enantioselectivities (93-96% ee) were obtained for a range of substrates.

Mesoporous aluminophosphate materials: influence of method of preparation and iron loading on textural properties and catalytic activity

In this paper the influence of the method of preparation and the iron loading on the textural properties and surface acidity of Iron aluminophosphates (FeAlP), [Fe x Al0.95P1, x = 0.01 mol−0.1 mol] was studied in order to learn how the preparation conditions and iron loading affect catalyst activity in transesterification reaction between diethyl malonate and benzyl alcohol. The catalysts were characterized by BET surface area, N2 sorption studies, NH3-TPD pXRD, SEM, and. FT-IR. Significant differences in the texture, surface acidity and adsorptive properties of FeAlP catalysts were found showing the influence of the preparation conditions and iron loading on the textural and surface properties of these catalysts. The textural and surface properties are correlated in the transesterification reaction between diethyl malonate and benzyl alcohol. FeAlP with 0.025 mol iron loading prepared by drop wise addition of ammonia, resulted a mesoporous material with uniform pore diameter (5–18 nm), higher surface area and higher surface acidity and hence catalytic activity towards the formation of Dibenzyl malonate. Fast addition of ammonia produced nonuniform porous material with lower surface acidity and low transesterification activity. Urea hydrolysis method yielded nonuniform porous materials with low surface area as well acidity.

비정질 인산알루미늄 철의 표면 성질 및 촉매 특성: 함유된 철의 양에 의한 효과

ABSTRACT. Iron aluminophosphates (FeAlP) with different percentage of iron were synthesized and characterized for their surfaceand bulk properties. The catalytic activity was determined in the transesterification of diethyl malonate with benzyl alcohol. Benzyl ethylmalonate and dibenzyl malonate were obtained as the only products. FeAlP with 0.025 mole % of iron was found to be distinc tly different in its textural and catalytic properties. Formation of diester was found to be favored by the acid sites of intermedi ate strength.The presence of hydrated alumina and the polycondensed phosphates in the materials reduced the catalytic activity of iron alumino-phosphates in transesterification reaction. Keywords: Amorphous aluminophosphates, Transesterification, Benzyl malonates, Iron loading 비정질 인산알루미늄 철의 표면 성질 및 촉매 특성 : 함유된 철의 양에 의한 효과 A. V. Vijayasankar, C. U. Aniz † , and N. Nagaraju * Department of Chemistry, Catalysis Research Laboratory, St. Joseph’s College Research Centre, 36. Lalbagh Road, Shanthi Nagar, Bangalore 560027, India

Catalytic Asymmetric Michael Reactions of Dibenzyl Malonate to α,β‐Unsaturated N‐Acylpyrroles Using a La(O‐iPr)3/Ph‐Linked‐BINOL Complex.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Development of new methods toward efficient immobilization of chiral catalysts

BINOL moieties are efficiently immobilized onto the surface of a micelle-derived spherical polymer and a monolayer-protected Au cluster (Au-MPC). Ti-BINOLate complexes generated from the BINOL immobilized polymer and Au-MPC are found to promote catalytic asymmetric alkylation of benzaldehyde with Et 2Zn to afford the adduct in up to 84% ee and 86% ee, respectively. Au-MPC-supported multicomponent asymmetric catalyst was prepared and used in the Michael reaction of 2-cyclohexen-1-one with dibenzyl malonate affording the adduct in up to 67% yield and 98% ee.

Catalytic asymmetric Michael reactions of dibenzyl malonate to α,β-unsaturated N-acylpyrroles using a La(O- iPr) 3/ Ph-linked-BINOL complex

Catalytic asymmetric Michael reactions of a malonate to acyclic α,β-unsaturated N-acylpyrroles as ester equivalent acceptors are described. A La(O- iPr) 3/( S, S)-linked-BINOL complex, which is suitable for Michael addition to cyclic enones, is not suitable for acyclic α,β-unsaturated N-acylpyrroles. A new ( S, S)- Ph-linked-BINOL chiral ligand was developed to improve enantioselectivity, and a La(O- iPr) 3/( S, S)- Ph-linked-BINOL complex with the addition of HFIP afforded Michael adducts in good yield and enantioselectivity (up to 96% ee).

Synthesis of (-)-Paroxetine

A six-step synthesis of the serotonin uptake inhibitor (-)-paroxetine features an organocatalytic asymmetric conjugate addition of dibenzyl malonate to α,β-unsaturated aldehyde A mediated by the proline-derived catalyst B. 15 examples are given with yields generally in the range 72-93% (er > 93:7).

Catalysis of the Michael Addition Reaction by Late Transition Metal Complexes of BINOL‐Derived Salens.

AbstractFor Abstract see ChemInform Abstract in Full Text.