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Search for "aldol reaction" in Full Text gives 122 result(s) in Beilstein Journal of Organic Chemistry.
Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source
Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221
- amount of reductant, as exemplified by the reductive aldol reaction of α,β-unsaturated nitriles catalyzed by cobalt using phenylsilane as the reductant [34]. Yamada found that the reductive carboxylation of α,β-unsaturated compounds with CO2 proceeded in the presence of Co catalysts and reductants
Recent applications of chiral calixarenes in asymmetric catalysis
Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117
- results clearly confirmed the cooperative effect and special role of the calixarene backbone. Aldol reaction Since chiral substituents and binding sites attached to the upper rim of the calixarene backbone can offer the full advantage of the unique inclusion properties of hydrophobic cavity, Wang et al
- prolinamide units located appropriate array on calixarene in the presence of 2 mol % of PhCOOH catalyzed the aldol reaction in excellent yield and high enantioselectivity. Under the optimized reaction conditions, the aldol reaction of aromatic aldehydes 72 with 70 and 71 afforded the adducts in moderate to
- respectively have been designed by Yilmaz et al. as shown in Figure 9 [65]. A new prolinamide derivative 92 with increased NH acidity has been synthesized from diformylcalixarene derivative 90 as shown in Scheme 24 [66]. Aldol reaction between 21 and 70 in water showed that catalyst 75 provided faster reaction
Recent advances in synthetic approaches for medicinal chemistry of C-nucleosides
Beilstein J. Org. Chem. 2018, 14, 772–785, doi:10.3762/bjoc.14.65
- methods of C2' substitution that involve conversion of the C2'-OH to a ketone followed by Me or F substitution [87][88][89][90][91][92][93][94]. Using the Mukaiyama aldol reaction, Peifer obtained a C2'-substituted ribonolactone, which can then be employed in C-nucleoside synthesis [75]. This involves
- '-substituted D-ribonolactone via Mukaiyama aldol reaction. A series of 2'-O-alkyl, alkyl, cycloalkyl and deoxy D-ribonolactone were synthesized using this method. B. Use of Hantzsch ester to obtain the β-anomer of C-nucleosides. Synthesis of carbocyclic C-nucleosides using cyclopentanone [53]. A. Nucleophlic
Nanoreactors for green catalysis
Beilstein J. Org. Chem. 2018, 14, 716–733, doi:10.3762/bjoc.14.61
- depicted in Figure 2, PQS (4a) has an OH moiety that allows for its linkage to the organocatalyst proline 4b. Also, PQS has a lipophilic component that acts as a reaction solvent for hydrophobic dienes. The latter feature allows aldol reactions to take place efficiently in water. The aldol reaction between
- asymmetric aldol reaction of cyclohexanone and 4-nitrobenzaldehyde [83]. Cross-linked polymersome nanoreactors were also used to perform asymmetric cyclopropanation reactions in water [15]. These products are highly desired intermediates in the preparation of agrochemicals and pharmaceuticals [84][85][86
Investigations towards the stereoselective organocatalyzed Michael addition of dimethyl malonate to a racemic nitroalkene: possible route to the 4-methylpregabalin core structure
Beilstein J. Org. Chem. 2018, 14, 553–559, doi:10.3762/bjoc.14.42
- , reduction, nitro-aldol reaction, and dehydration (Scheme 1). Methylation of the ester 2 in the alpha position proceeded easily with LDA as a base and methyl iodide as an alkylating agent. The ester functionality was then reduced with DIBAL in dichloromethane to afford aldehyde 4 in 90% yield. A base
- -mediated addition of nitromethane to the aldehyde 4 provided nitro alcohol 5. The somewhat lower yield (58%) of the aldol product 5 is likely caused by the reversibility of the nitro-aldol reaction. The yield of this reaction did not improve with longer time and unreacted aldehyde was still present in the
Syn-selective silicon Mukaiyama-type aldol reactions of (pentafluoro-λ6-sulfanyl)acetic acid esters with aldehydes
Beilstein J. Org. Chem. 2018, 14, 373–380, doi:10.3762/bjoc.14.25
- . The selectivity of these reactions depends on the geometry of the intermediate enolates. Here, we have reacted octyl pentafluoro-λ6-sulfanylacetate with substituted benzaldehydes and acetaldehyde under the conditions of the silicon-mediated Mukaiyama aldol reaction. The transformations proceeded with
- : aldol reaction; ester enolate; fluorine; SF5 compounds; stereochemistry; Introduction The classical acid- or base-catalyzed directed cross aldol reaction of an aldehyde and an enolizable second carbonyl compound is one of the most powerful and reliable carbon–carbon bond-forming transformations in
- chose the reaction of the less volatile octyl 2-(pentafluoro-λ6-sulfanyl)acetate (1) with p-nitrobenzaldehyde. Analogously to a protocol used by Ishihara et al. [35] for an Evans aldol reaction of trifluoropropanoic amides, we refluxed 1 equiv of ester 1 with 1.5 equiv trimethylsilyl
Recent developments in the asymmetric Reformatsky-type reaction
Beilstein J. Org. Chem. 2018, 14, 325–344, doi:10.3762/bjoc.14.21
- than the aldol reaction, especially in the case of heterogeneous conditions. Moreover, another limitation of the Reformatsky reaction is the requirement of an α-halogen in the Reformatsky reagent. Anyway, the Reformatsky reaction is versatile since it can occur through either intra- or intermolecular
The use of 4,4,4-trifluorothreonine to stabilize extended peptide structures and mimic β-strands
Beilstein J. Org. Chem. 2017, 13, 2842–2853, doi:10.3762/bjoc.13.276
- followed a general procedure to access to (2S,3S)-CF3-threonine through an aldol reaction of CF3CHO with the Ni(II) complex of the chiral Schiff base of glycine which was introduced by Belokon et al. [23][24]. The chiral auxiliary (S)-N-(2-benzoylphenyl)-1-benzylpyrrolidine-2-carboxamide (11) was obtained
- conditions gave the nickel Schiff base complex 12 in 71% yield as red crystals. The nucleophilic glycine equivalent 12 went through the aldol reaction with trifluoroacetaldehyde to give complex 13 in moderate yield (66%). Further hydrolysis of complex 13 led to the recovery of the chiral auxiliary 11 and
- obtained through the aldol reaction of trifluoroacetaldehyde with the Ni(II) complex of the chiral Schiff base of glycine. The conformational analysis of these pentapeptides was conducted by the combined use of NMR spectroscopy and molecular dynamics simulations. NMR conformational studies showed that the
Recent progress in the racemic and enantioselective synthesis of monofluoroalkene-based dipeptide isosteres
Beilstein J. Org. Chem. 2017, 13, 2637–2658, doi:10.3762/bjoc.13.262
- protection. Xaa-ψ[CF=C]-Pro The first asymmetric synthesis of Xaa-ψ[CF=C]-Pro was reported in 2012 by Chang’s group with the synthesis of MeOCO-Val-ψ[(Z)-CF=C]-Pro 93 (Scheme 18) [52]. Their synthesis started with a stereoselective aldol reaction using (L)-threonine to furnish a chiral β-hydroxy
Regiodivergent condensation of 5-alkoxycarbonyl-1H-pyrrol-2,3-diones with cyclic ketazinones en route to spirocyclic scaffolds
Beilstein J. Org. Chem. 2017, 13, 2179–2185, doi:10.3762/bjoc.13.218
- , bridged 1,3-oxazepine products 12 were formed in marginal yields, resulting from an initial aldol reaction involving the carbonyl group at C-3 of pyrroledione 9 and a subsequent intramolecular 6-endo-trig O-nucleophilic attack of the enol species at a conjugate unsaturated ketone moiety in the five
Mechanochemical synthesis of small organic molecules
Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186
- ]. In this section some of the most important C–C bond forming reactions and their advantages are discussed. Aldol reaction In 2000, Raston and Scott first reported the aldol condensation reaction using veratraldehyde, 4-phenylcyclohexanone and 1-indanone in the presence of NaOH in a vibrating ball mill
- -free conditions were performed using a combination of (S)-binam-L-Pro (A, 5 mol %) and benzoic acid (10 mol %) as organocatalyst [49]. Juaristi and co-workers investigated the mechanistic aspects of α,α-dipeptide derivatives of a (S)-proline- (A′)-catalyzed asymmetric aldol reaction (Scheme 2b) under
Solvent-free sonochemistry: Sonochemical organic synthesis in the absence of a liquid medium
Beilstein J. Org. Chem. 2017, 13, 1850–1856, doi:10.3762/bjoc.13.179
- ninhydrin and dimedone. Both systems were investigated in the complete absence of solvent and without the presence of any grinding media (such as inert silica beads) to help mediate the reaction. The aldol reaction was successfully carried out by twin screw extrusion, as I have reported previously [6]. The
- ultrasonic irradiation at room temperature that is instigating and accelerating this chemical reaction. Further confirmation that sonochemistry is a viable method to carry out solid state organic synthesis was obtained by carrying out an aldol reaction between ninhydrin and dimedone (Scheme 2). The optimised
- . Reaction mixture before and after ultrasonic irradiation for 60 minutes. 1H NMR spectrum of diimine 1 in CDCl3/EtOD. 1H NMR spectrum of 1,3-indandione 2 in DMSO-d6. Reaction between o-vanillin and 1,2-phenylenediamine by ultrasonic irradiation for 60 minutes. Aldol reaction between ninhydrin and dimedone
NHC-catalyzed cleavage of vicinal diketones and triketones followed by insertion of enones and ynones
Beilstein J. Org. Chem. 2017, 13, 1816–1822, doi:10.3762/bjoc.13.176
- , the reaction efficiency was much lower than that of benzil (1a) (Scheme 4). The only isolated by-product in the reaction of 5a was bicyclo[3.2.1]octanone 8 (ca. 10%), which was formed by competitive tandem Michael–aldol reaction [21]. Cycloheptane-1,2-dione (5b) and cyclododecane-1,2-dione (5c) gave
The chemistry and biology of mycolactones
Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159
Total syntheses of the archazolids: an emerging class of novel anticancer drugs
Beilstein J. Org. Chem. 2017, 13, 1085–1098, doi:10.3762/bjoc.13.108
- a boron-mediated anti-aldol reaction [67] of lactate-derived ethyl ketone 13 with aldehyde 12, which in turn was available from aldehyde 9 by HWE olefination. This Paterson aldol reaction and related aldol reactions, which have been amply used by the Menche group [68][69][70], proceeded with
Synthesis of D-manno-heptulose via a cascade aldol/hemiketalization reaction
Beilstein J. Org. Chem. 2017, 13, 795–799, doi:10.3762/bjoc.13.79
- aldol/hemiketalization reaction of a C4 aldehyde with a C3 ketone provides the differentially protected ketoheptose building block, which can be further reacted to furnish target D-manno-heptulose. Keywords: aldol reaction; cascade reaction; D-manno-heptulose; higher-carbon sugar; ketoheptose
- chain elongations of aldoses employing the Henry reaction, the aldol reaction, and the Wittig reaction for the preparation of ketoheptoses [20][21][22], sugar lactones were also often utilized for the synthesis of D-manno-heptulose via reactions with C-nucleophiles or conversion into exocyclic glycals
- on TLC monitoring. Given that the C4 aldehyde 3 was unstable upon purification by silica gel column chromatography, it was immediately used for the subsequent coupling after the extraction procedure. The aldol reaction of aldehyde 3 with the readily available ketone 4 [42][43] under the catalysis of
Formose reaction controlled by boronic acid compounds
Beilstein J. Org. Chem. 2016, 12, 2668–2672, doi:10.3762/bjoc.12.263
- formose reaction consists of several elemental reaction steps, e.g., acyloin condensation, aldol reaction, retro-aldol reaction, aldose–ketose isomerization, and Cannizzaro reaction, and the product, formose, is a complicated mixture of more than thirty species of sugars and sugar alcohols including non
Formose reaction accelerated in aerosol-OT reverse micelles
Beilstein J. Org. Chem. 2016, 12, 2663–2667, doi:10.3762/bjoc.12.262
- rate-determining step of the formose reaction. It is known that glycolaldehyde acts as a cocatalyst. Thus, when the concentration of glycolaldehyde reaches a certain level, formaldehyde is consumed rapidly to form a complicated mixture of sugars predominantly via aldol reaction and aldose–ketose
- transformation in the sugar formation period. When formaldehyde is consumed quantitatively, the reaction mixture turns yellow. In the sugar degradation period, the sugars formed are decomposed dominantly through cross-Cannizzaro reaction and retro-aldol reaction to form a more complicated reaction mixture. The
Towards the development of continuous, organocatalytic, and stereoselective reactions in deep eutectic solvents
Beilstein J. Org. Chem. 2016, 12, 2620–2626, doi:10.3762/bjoc.12.258
- . Keywords: continuous process; DES; organocatalysis; proline; stereoselective aldol reaction; Introduction The aldol reaction is a powerful synthetic tool to create new C–C bonds [1]. It offers several possibilities to control the stereochemical outcome of the process and to afford stereochemically defined
- chiral products [2]. Among all the possible options, the L-proline-catalysed stereoselective cross-aldol reaction remains the greener choice. After the pioneering works by List and Barbas [3], a huge effort was made by the scientific community to improve both the yield and the stereoselectivity of the
- eutectic mixtures as reaction media (Table 1) [40]. The behaviour of DES mixtures A–E in the proline-catalysed model aldol reaction between cyclohexanone and 4-nitrobenzaldehyde was preliminarily investigated under standard batch conditions (Scheme 1). In our hands, the reaction proceeded completely in 20
Synthesis of polyhydroxylated decalins via two consecutive one-pot reactions: 1,4-addition/aldol reaction followed by RCM/syn-dihydroxylation
Beilstein J. Org. Chem. 2016, 12, 2602–2608, doi:10.3762/bjoc.12.255
- 1,4-addition of vinylmagnesium bromide to sugar-derived cyclohexenone, followed by an aldol reaction with a derivative of but-3-enal. The obtained diene is then subjected to an assisted tandem catalytic sequence: ring-closing metathesis with the subsequent reuse of the Ru-catalyst in the syn
- possibility of using a copper-catalyzed one-pot 1,4-addition of vinylmagnesium bromide to sugar-derived cyclic α,β-unsaturated ketones (such as 9), followed by an aldol reaction with an optically pure derivative of but-2-enal 10 to obtain a mixture of diastereomeric dienes, such as 11 (Scheme 2). As a result
- of this transformation, three new stereogenic centers are generated. A copper-catalyzed 1,4-addition of organometallic reagents to cyclic α,β-unsaturated ketones, followed by an aldol reaction has been already used in the synthesis of complex natural products [26][27][28][29][30][31][32][33
Enduracididine, a rare amino acid component of peptide antibiotics: Natural products and synthesis
Beilstein J. Org. Chem. 2016, 12, 2325–2342, doi:10.3762/bjoc.12.226
- synthetically broken down into tripeptides 78 and 79 (Scheme 15). Tripeptide 78 was further disconnected into protected serine 80 and protected β-hydroxyenduracididine residues 81 and 82. The synthesis of key amino acids 81 and 82 was based on an aldol reaction between protected aldehyde 83 and glycine 84
A chiral analog of the bicyclic guanidine TBD: synthesis, structure and Brønsted base catalysis
Beilstein J. Org. Chem. 2016, 12, 1870–1876, doi:10.3762/bjoc.12.176
- base the retro-aldol reaction of some cycloadducts with kinetic resolution of the enantiomers. In three cases, the retro-aldol products (48–83% ee) could be recrystallized to high enantiopurity (≥95% ee). The absolute configuration of several compounds is supported by anomalous X-ray diffraction and by
- base-catalyzed retro-aldol reaction and they are not converted backwards into Diels–Alder adducts under such conditions [19][25][26]. Our results shown below give further support to this view. Riant, Kagan and Ricard have demonstrated for the first time that deprotonated anthrones may coordinate to
- moderate stereoselectivity is superimposed with a kinetic resolution of enantiomers in the subsequent retro-aldol reaction. Both are catalyzed by the chiral guanidine 10. As a result, the numbers shown in Table 1 are not constant but depend on the relative turnover of each reaction. When rac-25 reacted
Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update
Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98
- products in good yields and with excellent enantioselectivities (Scheme 16). In 2013, Ishimaru and co-workers developed a N-aryl-L-valinamide (cat. 5)-catalyzed asymmetric aldol reaction of isatins with ketones, affording the products in excellent yields and with up to >99% ee (Scheme 17) [33]. The
- reaction was performed under mild conditions using PTSA·H2O as the additive. Subsequently, the asymmetric aldol reaction of aliphatic aldehydes with isatins was achieved by the same group by using a structurally slightly modified organocatalyst (cat. 5, Scheme 18) [34]. Malonic acid as the additive and
- hydrogen bonds with organocatalyst (cat. 5) and isatin substrate. A novel N-prolinylanthranilamide-based pseudopeptide organocatalyst (cat. 6) was designed by Bunge et al. for the enantioselective aldol reaction of 2,2-dimethyl-1,3-dioxan-5-one with isatins, affording the products in good yield and with
Scope and mechanism of the highly stereoselective metal-mediated domino aldol reactions of enolates with aldehydes
Beilstein J. Org. Chem. 2016, 12, 813–824, doi:10.3762/bjoc.12.80
- ; domino aldol; metal enolate; tetrahydropyran; Introduction Since its discovery in the late nineteenth century the aldol reaction has become one of the most powerful tools in the field of carbon–carbon bond formation [1][2][3][4][5]. It is widely used in the formation of many natural products [6][7][8][9
- ][10][11], stereoselective syntheses [12][13][14][15][16], and tandem reactions [17][18][19]. While the latter processes usually comprise only one aldol reaction, tandem reaction sequences containing two consecutive aldol steps are mostly limited to the trimerization of enolates [20][21][22]. Metal
- , Ga, In, Ti, Zr, Sn), and various aldehydes and ketones is studied experimentally and computationally. Results Metal effect The experiments were performed to screen suitable metal fragments for their ability to promote the domino aldol reaction by studying the reaction between propiophenone (1a) and
Muraymycin nucleoside-peptide antibiotics: uridine-derived natural products as lead structures for the development of novel antibacterial agents
Beilstein J. Org. Chem. 2016, 12, 769–795, doi:10.3762/bjoc.12.77
- steps (Scheme 1) [87][88]. This was followed by an aldol reaction of aldehyde 2 with N,N-dibenzylglycine tert-butyl ester (3) [89] and LDA as a key step of the synthesis (Scheme 1). The resultant products were the two 5'-epimers 4 (5'R,6'S) in 31% yield and 5 (5'S,6'S) in 14% yield, which could be
- glycine (100). Hence, LipK was revealed to be a transaldolase mediating a retro-aldol reaction of L-threonine (119) towards the enol(ate) and acetaldehyde (120), followed by a stereoselective aldol addition of the former to uridine-5'-aldehyde 99 (Scheme 12). Using synthetic reference compounds, it could
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