Top PDF Process for the synthesis of α, β-unsaturated esters

Process for the synthesis of α, β unsaturated esters

Process for the synthesis of α, β unsaturated esters

In one embodiment, the process includes the steps of: exposing a mixture of a mono-ole?n-ester and Fe(CO)5 to ultraviolet radiation; and adding a coordinating ligand or oxidiZing age[r]

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Synthesis, Reactions and Biological Importance of α, β-Unsaturated Carbodithioate Esters: A Review

Synthesis, Reactions and Biological Importance of α, β-Unsaturated Carbodithioate Esters: A Review

Interestingly, α, β-unsaturated thioesters have marked reactivity as Michael acceptors and they are proved to be excellent substrates in the synthesis of several natural products [22]. Although, it is a very useful intermediate, traditional syntheses of thioesters are encountered with the occasional difficulties such as 1,4-addition of thiolate and subsequent separation from the main product [23]. Olefin cross-metathesis has been elegantly explored to construct α, β-unsaturated thioesters using thioacrylate [24]. Encouraged by the success of synthesis of α, β-unsaturated esters, A.R. Mohite et al [25]. planned to extend the protocol for the straightforward synthesis of α, β-unsaturated thioesters using the optimized reaction conditions for esters. To compare the reactivity and to extend the application, thiols 13 (1 eq.) were treated with few benzylidene derivative of MA 12 under optimized reaction conditions (Scheme 4). The corresponding α, β-unsaturated thioesters 14 were obtained in good to excellent yields (76–90%) in just 30 min (Scheme 4).
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α,β unsaturated acyl ammonium intermediates in asymmetric organocatalysis

α,β unsaturated acyl ammonium intermediates in asymmetric organocatalysis

4.4 Reaction Scope 4.4.1 Enone-malonate synthesis via cross-metathesis In order to investigate the scope of the MML process with respect to the nucleophile- electrophile reactant, an optimisation of the starting material synthesis was carried out. It was not possible to generate the enone-malonate starting materials via ozonolysis/Wittig procedures due to the unstable nature of intermediate aldehydes, leading to no formation of the desired products. Grubbs II-catalysed cross metathesis between allylester 382 and methyl vinyl ketone 383 afforded the desired product 370, but the conversion was low so a range of alternative catalysts developed by the Nolan group 130 were tested to try and improve the efficiency of the reaction. xviii These catalysts have been shown to be highly effective in cross-metathesis processes however in our reaction M20 385 and M31 387 gave poor conversion to product 370 (12-27%, Scheme 112). M23 386 and M2 388 afforded higher conversions of 41% and 56% respectively on a 0.5 mmol scale. However when the M2-catalysed reaction was scaled up to 15 mmol the conversion dropped to 39%. No competing homocoupling of allyl ester 382 was observed and the reaction did not tolerate lower catalyst loadings. Increased and decreased equivalents of methyl vinyl ketone 383 were also investigated however no improvement to the conversion was achieved.
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Synthesis of Allylic Amines by Asymmetric Transfer Hydrogenation of α,β-Unsaturated N-(tert-Butylsulfinyl)imines

Synthesis of Allylic Amines by Asymmetric Transfer Hydrogenation of α,β-Unsaturated N-(tert-Butylsulfinyl)imines

In our opinion, the transformation described herein represents a very efficient methodology for the preparation of allylic amines with very high optical purities from easily available enones. Our ATH process is more convenient than the few procedures of selective reduction of the C=N bond of conjugated N-(tert-butylsulfinyl)imines reported so far, which employ stoichiometric amounts of aluminum or boron reducing agents. Some advantages of our ATH protocol in comparison with the reported examples are: (a) it is much more versatile, since a broader variety of allylic amines can be prepared with excellent ee’s; (b) our solvent and hydrogen source is isopropyl alcohol, which is environmentally friendly and appropriate for industrial scale applications; 30 (c) the ATH process is promoted by a catalytic amount of a ruthenium complex bearing a very cheap achiral ligand, which is very convenient from an economical point of view. The easy availability of α,β-unsaturated ketones, their straightforward transformation into both enantiomers of N-(tert-butylsulfinyl)imines and the very high diastereoselectivity of our ATH procedure can convert our proposal into a very useful tool for organic synthesis.
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Generation of Enamides and Enol esters: Application to Oxazole and α-Naphthol Synthesis

Generation of Enamides and Enol esters: Application to Oxazole and α-Naphthol Synthesis

Fig 1: Biologically important naphthol derivatives The profound usage of naphthalene derivatives particularly, naphthols stimulates the development of new and complementary methods for their synthesis. Stepwise electrophilic aromatic substitution to a naphthalene ring is recognized as a conventional method to access polysubstituted naphthalenes by functionalization of aromatic C-H bonds to C-C and C-N/O bonds. Complex reaction conditions and frequent formation of regioisomeric mixtures are the inevitable drawbacks associated with the above process. 5 Thus, a number of eminent methods including the Diels–Alder reaction, Hauser phthalide annulations, 6 rearrangement of cyclopropanes or cyclobutanes, and acid-catalyzed cyclization reactions have been developed. 7 Numerous transition metal catalysts encompassing Cr, Mn, Pd, Rh, and Cu were also successfully employed for the construction of naphthalene rings from their monocyclic precursors owing to their advantages over the regioselectivity problem. 8 In contrast, the regioselective synthesis of naphthols with predetermined substituents is less well endowed with literature precedents. Some elegant methods of naphthol synthesis are presented below.
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Aryloxide facilitated catalyst turnover in enantioselective α,β unsaturated acyl ammonium catalysis

Aryloxide facilitated catalyst turnover in enantioselective α,β unsaturated acyl ammonium catalysis

functionalized products (Table 2). The use of primary and secondary amines gave secondary and tertiary amides 10–14 in good yield, whilst addition of methanol gave methyl ester 15. All amide and ester products were obtained with high enantioselectivity indicating no significant loss in enantiopur- ity during the derivatization process. The scope of b- substituted a,b-unsaturated aryl esters amenable to the process was then investigated. Methyl-, isopropyl- and benzyl esters gave the addition products 16–18 in good yield and with excellent enantioselectivity. The incorporation of amides at the b-position was also well tolerated, giving unsymmetrical succinamide derivatives 19 and 20 in equally high yield and levels of enantiocontrol. The absolute config- uration of 19 was confirmed by single crystal X-ray analysis, with all other examples assigned by analogy. [17] Limitations of this methodology include incompatibility of substrates such as g-keto ester derivative 22, which gave a complex mixture of products, and cinnamic acid derivative 23, which was com- pletely unreactive. A derivative bearing b-alkyl substitution however gave product 21 with excellent enantiocontrol, albeit in low yield. The synthesis of a quaternary stereogenic carbon centre was also attempted, however application of b,b- disubstituted derivative 24 failed to give the desired Michael addition product.
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Chemoenzymatic approach toward the synthesis of 3-O-(α/β)-glucosylated 3-hydroxy-β-lactams

Chemoenzymatic approach toward the synthesis of 3-O-(α/β)-glucosylated 3-hydroxy-β-lactams

respectively, but they can be exploited for synthetic purposes under speci fic process conditions as well. A critical property to consider when choosing a suitable candidate for catalyzing the envisioned glycosylation reactions is the substrate promiscuity. Indeed, acceptor sites that are strictly speci fic toward a narrow group of molecules will be less likely to bind the rather challenging cis-3-hydroxy- β-lactam targets. Therefore, two biocatalysts that are known to have a broad acceptor scope were selected. The sucrose 6 ′-phosphate phosphorylase from T. thermosaccharolyticum (TtSPP) is an appealing enzyme for the synthesis of α-glucosides considering the use of sucrose as a cheap and renewable donor substrate, and shows activity on a diverse range of small molecules with retention of the anomeric con figuration. 63 Moreover, a mutant of TtSPP (R134A) was rationally designed previously in our laboratory to widen the entrance to the active site, triggering a ffinity for bulky polyphenols such as resveratrol. 64 The selected option for the synthesis of β-bonded adducts concerns the stevioside glucosyltransferase from S. rebaudiana (UGT- 76G1Sr), which has been employed successfully on structures such as branched alcohols, flavonoids, terpenoids, and more. 65 Although its need for the expensive donor substrate uridine diphosphate glucose (UDP-glucose) is a major drawback, this Scheme 3. Carbohydrate-Active Enzymes Used in Glycosylation Reactions (A = Acceptor; P i = Inorganic Phosphate; UDP =
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Multiple roles of aryloxide leaving groups in enantioselective annulations employing α,β unsaturated acyl ammonium catalysis

Multiple roles of aryloxide leaving groups in enantioselective annulations employing α,β unsaturated acyl ammonium catalysis

homoanhydrides, demonstrating the wide applicability of the method. Finally, the phenol derivative produced upon proton- ation of the aryloxide during the reaction was shown to act as a Brønsted acid, which promoted an isothiourea-catalysed kinetic resolution of benzoxazole-derived dihydropyranones. Overall, this work provides a concise and efficient method for the synthesis of polyuorinated heterocyclic products in high yield and enantioselectivity. Identication of the multiple roles of the aryloxide leaving group in this process should inform future work in this area and provide inspiration for new reaction design. 27
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Novel β' and α'/β' sialon ceramics

Novel β' and α'/β' sialon ceramics

boundary diffusion proc< . although full densificatl can occur without the transformation becoming complete. 4. Methods of Producing Silicon Nitride-based Components The earliest successful attempts at fabricating solid components followed from a natural extension of the nitriding process involved in synthesis of the Si3N 4 powder itself. In reaction bonding, the raw s i l i c o n powder is first formed into the req u i r e d s h ape u s i n g c o n ventional f orming techniques (e.g. isostatic pressing, s l i p casting, or injection moulding), then the compact is nitrided between 1150°C and 1400°C to give a bonded mixture of a and B-Si 3N 4 as the reaction product (i.e. Reaction bonded silicon nitride - RBSN). The main advantage of this method is that only slight shrinkage occurs w h i c h allows f a i r l y c o m p l i c a t e d shapes to be f abricated, w i t h reasonable tolerance, quite cheaply. Unfortunately, it is difficult to nitride thick sections and the product always contains 15- 3 0 % porosity which reduces its mechanical strength, although much of this strength is retained to temperatures in excess of 1400°C and the absence of any amorphous intergranular phase affords it excellent oxidation resistance.
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Isothiourea catalysed enantioselective Michael addition of N heterocyclic pronucleophiles to α,β unsaturated aryl esters

Isothiourea catalysed enantioselective Michael addition of N heterocyclic pronucleophiles to α,β unsaturated aryl esters

Introduction Catalytic enantioselective Michael addition of enolate equiva- lents to a , b -unsaturated carbonyl compounds represents an efficient methodology for stereoselective C–C bond formation. 1 Within this eld, considerable advances in catalytic enantiose- lective Michael additions to enals and enones have been re- ported. 2 Typical strategies involve activation of the Michael acceptor through iminium ion formation, 3 H-bonding organo- catalysis, 4 or Lewis acid catalysis. 5 In comparison to enals and enones, the intrinsic recalcitrance of a,b-unsaturated esters 6 represents a signicant challenge in enantioselective catalysis (Scheme 1a). 7 Established metal-based catalytic systems allow, for example, conjugate additions of aryl boronic acids and Grignard reagents to a,b-unsaturated esters. 8 Broader reactivity has been targeted through developing the use of ester surro- gates such as N-acylpyrroles, 9 2-acyl imidazoles, 10 activated imides 11 and b , g -unsaturated acyl phosphonates. 12 Catalytic strategies using these motifs typically rely upon two-point binding between the enoyl substrate and either a Lewis acidic metal catalyst 13 or a H-bond donor organocatalyst. 14 Despite these advances, only limited organocatalytic strategies have been developed that allow activation of a,b-unsaturated ester substrates, with the current state-of-the-art strategies having
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Green approach for the synthesis of some new  α,β-unsaturated ketimines under water

Green approach for the synthesis of some new α,β-unsaturated ketimines under water

Available online: 04 February 2012. ABSTRACT. An environmentally benign and efficient synthesis of some α,β-unsaturated ketimines from new 2-hydroxychalcone and different aromatic amines under water suspension. The remarkable advantages offered by this method are environmentally friendly, short reaction times, non-hazardous, simple work-up procedure and good to excellent yields of products.

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Organocatalytic Michael addition–lactonisation of carboxylic acids using α,β unsaturated trichloromethyl ketones as α,β unsaturated ester equivalents

Organocatalytic Michael addition–lactonisation of carboxylic acids using α,β unsaturated trichloromethyl ketones as α,β unsaturated ester equivalents

Sequential addition of two different nucleophiles to a dihydropyranone gives the corresponding differentially substituted diacid derivative. Introduction Lewis base organocatalysis is a powerful method for the stereoselective construction of carbon-carbon bonds. 1 In this regard, catalytic asymmetric conjugate additions of ammonium and azolium enolates to electron-deficient alkenes have been widely explored. 2,3 However, the use of α,β-unsaturated esters and amides as Michael acceptors in such processes remains a challenge due to the decreased electrophilicity of such substrates. Strategies to overcome this problem typically make use of more reactive α,β-unsaturated ester equivalents such as N-acylpyrroles 1, 4 2-acyl imidazoles 2, 5 activated imides 3 6 and
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Epoxidation of unsaturated esters

Epoxidation of unsaturated esters

the most prominent of which is the manufacture of epoxy resins. The potential of epoxidised fatty materials was quickly recognised, Vernonia anthelmintica oil with its high epoxy acid content (70%) has been evaluated as a stabiliser and plasticiser for polyvinyl chloride^^'^^. The stabilising qualities are mainly due to the ability of the epoxy groups to react with residual hydrogen chloride in the polymer with chlorohydrin formation. Soybean, cottonseed and linseed oils, to name just a few oils rich in unsaturated fatty acids, are commercially epoxidised for use as stabilisers and plasticisers, The epoxy derivatives serve also as monomers for curing with agents like phthalic anhydride to give epoxy resins'”' a n d are valuable intermediates for a great number of chemicals.
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Addition of dithi(ol)anylium tetrafluoroborates to α, β-unsaturated ketones

Addition of dithi(ol)anylium tetrafluoroborates to α, β-unsaturated ketones

© 2018 Huang et al.; licensee Beilstein-Institut. License and terms: see end of document. Abstract In the presented study, dithi(ol)anylium tetrafluoroborates are added to α,β-unsaturated ketones in a Michael-type reaction yielding diverse substituted ketene diothi(ol)anes. The reactions proceed at room temperature in 1 or 13 h without the need of further addi- tives. The presented procedure is in particular useful for dithi(ol)anylium tetrafluoroborates without electron-withdrawing groups in α-position. This is advantageous with respect to previous approaches, which were limited to the use of ketene dithioacetals substi- tuted with electron-withdrawing groups. Aiming for the systematic investigation of possible steric and electronic influences on the outcome of the reaction, various combinations of electrophiles and nucleophiles were used and the results of the reactions were compared based on the type of the used dithioacetal. The scope of the presented procedure is shown with four additional transfor- mations including the use of additional electrophiles and nucleophiles, the use of a chiral auxiliary and subsequent reduction of selected products. Additionally, we extended the reaction to the synthesis of diene dithiolanes by addition of an ynone to α-alkyl or aryl-substitued dithiolanylium TFBs.
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Microwave induced novel synthesis and characterization of 3,5-diaryl-∆2-isoxazoline” from α, β-unsaturated carbonyl compounds

Microwave induced novel synthesis and characterization of 3,5-diaryl-∆2-isoxazoline” from α, β-unsaturated carbonyl compounds

Conclusion We have developed a facile rapid one-pot economic methodology for the synthesis of substituted 3,5-diaryl-∆ 2 - isoxazoline (4a-k) through by the reaction of α,β-unsaturated carbonyl compounds with hydroxyl amine hydrochloride in presence of base/ basic Al 2 O 3 using MWI. For the synthesis of isoxazolines (4a-k) microwave assisted solid support methodusing basic alumina was found better method in comparison to classical as well as solution phase MWl method and gave shorter reaction time, higher yield and solvent free condition with easy experimental manipulation. The synthesized compound may serve as useful intermediate for the synthesis of structurally diverse heterocyclic compounds. Significant anti- microbial activity was observed with synthesized compounds against bacteria and fungi.
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STEREOSELECTIVE SYNTHESIS OF α,β-UNSATURATED δ-LACTONE CONTAINING NATURAL PRODUCTS, SYNTHESIS OF 12-MEMBERED MACROLACTONE AND ITS C12 EPIMER AND ATTEMPTED SYNTHESIS OF OKASPIRODIOL

STEREOSELECTIVE SYNTHESIS OF α,β-UNSATURATED δ-LACTONE CONTAINING NATURAL PRODUCTS, SYNTHESIS OF 12-MEMBERED MACROLACTONE AND ITS C12 EPIMER AND ATTEMPTED SYNTHESIS OF OKASPIRODIOL

yield. In the present study on the first synthesis of 1, it was planned to undertake a macrocyclisation protocol for the macrolide ring construction instead of a macrolactonisation protocol. It was then planned to use of RCM protocol for the macrocyclisation step. In accordance with the synthetic strategy, finally, ester 16 on treatment with Grubbs 15 second generation catalyst in CH 2 Cl 2 at reflux for 12 h afforded 17 in 72% yield. Later, deprotection as well as double bond redunction of macrolide 17 by using Pd/C in MeOH under hydrogen atmosphere for 2 h to gave alcohol 18 in 82%
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Merging domino and redox chemistry: Stereoselective access to di- and trisubstituted β,γ-unsaturated acids and esters

Merging domino and redox chemistry: Stereoselective access to di- and trisubstituted β,γ-unsaturated acids and esters

E-mail: fgarcia@ipna.csic.es;dtejedor@ipna.csic.es Homepage: http://www.ipna.csic.es/dept/qbb/qb/ [§] These authors have contributed equally to this work Abstract: This work shows how the coupling of a MW-assisted domino reaction and an internal neutral redox reaction constitutes an excellent manifold for the stereoselective synthesis of di- and trisubstituted olefins featuring a malonate unit, an ester or a free carboxylic acid at the allylic position.

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Conjugate Addition of Indoles to α,β Unsaturated Ketones Using Bismuth (III) Bromide

Conjugate Addition of Indoles to α,β Unsaturated Ketones Using Bismuth (III) Bromide

Keywords Bismuth, Bismuth Bromide, Conjugate Addition, Green Chemistry, Indoles Indoles and their derivatives are of considerable interest in medicinal chemistry due to the wide range of biological activity they exhibit. Indoles undergo elec- trophilic substitution at the 3-position and hence a variety of methods have been developed for the synthesis of 3-substituted indoles [1]-[8]. The conjugate addi- tion of indoles to chalcones (substituted phenyl styryl ketones) leads to 3-indolyl ketones, compounds that exhibit biological activity [9]. Hence a variety of cata- lysts have been used to catalyze such additions. Some examples include FeCl 3
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An investigation of support effects on the Pt-catalysed selective transformation of α,β-unsaturated substrates

An investigation of support effects on the Pt-catalysed selective transformation of α,β-unsaturated substrates

3 reaction schemes. 8,9 Consequently, a fundamental understanding of the active site and reaction network is pivotal for improving catalyst design. The definition of a catalyst is any reagent or material which increases the rate of chemical reaction by the lowering the activation energy barrier for the rate determining step of said reaction, without being consumed. This rate enhancement is achieved by providing an alternative mechanism, proceeding through a transition state of lower energy. In doing so, this can enable reactions normally hindered by slow reaction kinetics/barriers, to proceed with enhanced rate under more amiable conditions, wrt to the uncatalysed reaction. However, as substrate complexity increases, multiple reaction pathways present themselves resulting in the possibility of various side products. As each product has an inherent activation energy barrier, the presence of a catalyst can be used as a tool to drive the formation of specific products, based solely on energetic favourability. 10,11 In this instance, intelligent design must be employed to tune final product selectivity and improve system efficiency. Applying this fundamental property, catalytic systems are utilised in a wide array of situations, from large- scale cracking of long-chain alkanes and crude oil in the petrochemical sector, 12 to the promotion of the Heck 13 and Friedel-Crafts 14 reactions in fine chemical synthesis, but perhaps most famously in the after-treatment of partially converted emission gases in internal combustion engines. 15,16 Unaided such processes could not implemented on such a substantial scale without catalyst exploitation.
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Hydrogenation of α,β-unsaturated aldehydes and lipids by water-soluble transition metal complex catalysts

Hydrogenation of α,β-unsaturated aldehydes and lipids by water-soluble transition metal complex catalysts

New complexes were synthesized according to the known [1] method of synthesis of the analogous [RuH(OAc)(mtppms) 3 ] complex. The structures of the three complexes were characterized by IR and/or 1 H- and 31 P-NMR spectroscopy. According to the IR data the bidentate coordination of the carboxylate ligand was established in case of all three complexes. Due to the spectroscopic data following general structure was suggested for the complexes (Figure 1).

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