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Search for "enone" in Full Text gives 173 result(s) in Beilstein Journal of Organic Chemistry.
Synthesis of a sucrose dimer with enone tether; a study on its functionalization
Beilstein J. Org. Chem. 2014, 10, 1246–1254, doi:10.3762/bjoc.10.124
- sucrose aldehyde afforded a dimer composed of two sucrose units connected via their C6-positions (‘the glucose ends’). The carbonyl group in this product (enone) was stereoselectively reduced with zinc borohydride and the double bond (after protection of the allylic alcohol formed after reduction) was
- shown in Figure 2. The properly activated sugar is converted into phosphorane or phosphonate which – upon reaction with an aldehyde derived from another monosaccharide – provides higher carbon sugar (HCS) enone [16][17][18]. Application of this methodology to selectively protected 2,3,3’,4,4’-penta-O
- the ‘fructose end’ providing alcohol 6 [8]. This alcohol was converted into aldehyde 7 [21] (route a in Scheme 1) and separately into phosphonate 9 (route b). Reaction of both synthons under the mild PTC conditions [22][23][24] afforded the respective enone 10 in good yield (Scheme 1
Visible-light-induced, Ir-catalyzed reactions of N-methyl-N-((trimethylsilyl)methyl)aniline with cyclic α,β-unsaturated carbonyl compounds
Beilstein J. Org. Chem. 2014, 10, 890–896, doi:10.3762/bjoc.10.86
- -aminomethyl radicals [43][44][45] to enones. N-Methyl-N-((trimethylsilyl)methyl)aniline (5) for example served as substrate for the alkylation of 2-cyclohexenone (6) employing iridium catalyst 7. When using the amine as the limiting reagent and an excess of enone (1.5 equiv) product 8 was obtained in 70
- and delivered product 14 in 41% yield. Addition to cyclic α,β-unsaturated ketones Based on the results obtained with five-membered lactone 9, it was suprising to note that the related five-membered enone, 2-cyclopentenone (15), delivered mainly the direct addition product 17 instead of the tricyclic
Simple two-step synthesis of 2,4-disubstituted pyrroles and 3,5-disubstituted pyrrole-2-carbonitriles from enones
Beilstein J. Org. Chem. 2014, 10, 466–470, doi:10.3762/bjoc.10.44
- closure to furnish 3,4-dihydro-2H-pyrrole-2-carbonitriles 6 after reprotonation [36]. If the products are devoid of an additional substituent in 2-position, the cyclocondensation can be simply effected by refluxing a mixture of the enone 1 and aminoacetonitrile hydrochloride (2) in pyridine. The base
Additive-assisted regioselective 1,3-dipolar cycloaddition of azomethine ylides with benzylideneacetone
Beilstein J. Org. Chem. 2014, 10, 352–360, doi:10.3762/bjoc.10.33
- -donating groups (Table 3, entries 6, 10 and 11). When the hydroxy group was introduced to the para-position on the phenyl ring of enone, the best regioisomeric ratio was obtained and only one single regioisomer 4k was isolated (Table 3, entry 11). Surprisingly, the addition of 4-nitrobenzoic acid only
Synthesis of the B-seco limonoid core scaffold
Beilstein J. Org. Chem. 2014, 10, 194–208, doi:10.3762/bjoc.10.15
- quaternary centers at the ring junction. We decided to start the sequence with known enone 15 [39] and intended to construct the all-carbon quaternary center at C13 by substrate controlled α-functionalization. The second quaternary center at C14 might be established by 1,2-addition and finally, ring-closing
- systems, presenting appropriate stereogenic substitution at the C ring system. After merging these alcohols with an undecorated A ring, the resulting allyl vinyl ethers could serve as suitable rearrangement precursors. The synthesis of 19 and 20 commenced with enone 15 [39], which was prepared from
- rearrangements of the model substrates with an undecorated A ring, we attempted to access the B-seco limonoid scaffold by an analogous rearrangement of bicyclic precursor 66 (Scheme 8). The elaboration of the required bicyclic system commenced with enone 15 (Scheme 8). Initially, we envisaged an α-vinylation via
Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis
Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14
- to give tricycle 111. The enol ether moiety was reduced using NaCNBH3, followed by allylic Riley oxidation and PCC-mediated enone formation. Copper-catalyzed conjugate addition in the presence of TMSCl [105] yielded silyl enol ether 112. Subsequent introduction of the side chain in 113 via a Claisen
- , reduction of the remaining double bond and subsequent Krapcho decarboxylation [132] resulted in less functionalized ketone 150. Aldol condensation with furfural followed by O-allylation and Claisen rearrangement furnished enone 151. Standard functional group interconversiones were used to access TIPS
- yielded intermediate cis-divinylcyclopropane 164, which underwent the desired rearrangement at remarkably low temperature to yield bicycle 165. Selective hydroboration/oxidation (directed through participation of the untouched double bond) followed by Swern oxidation gave ketone 166. The enone system 167
Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products
Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6
Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C2-symmetric building block: a strategy for the synthesis of decanolide natural products
Beilstein J. Org. Chem. 2013, 9, 2544–2555, doi:10.3762/bjoc.9.289
- -butanol solvent mixture than the analogous enone reductions outlined in Scheme 3 and Table 2. Compared to these reactions, the saturated ester 25 was obtained in a nearly quantitative yield using half the amount of Cu precatalyst and BDP ligand. In order to obtain enantiomerically pure 21, an enzyme
A combined continuous microflow photochemistry and asymmetric organocatalysis approach for the enantioselective synthesis of tetrahydroquinolines
Beilstein J. Org. Chem. 2013, 9, 2457–2462, doi:10.3762/bjoc.9.284
- hand, the substrate scope of this new photocyclization–asymmetric transfer hydrogenation sequence was examined. The results are summarized in Table 2. In general, different 2-aminochalcones bearing substituted aromatic residues on both ketone and enone moieties underwent the desired photocyclization
An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles
Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265
- pyridines can be furnished by employing an amino-enone or aminonitrile compound with a 1,3-dicarbonyl moiety. In both cases a subsequent oxidation step is usually required to convert the initially formed dihydropyridine intermediate into the desired aromatic pyridine. Some additional but much less common
- condenses by Michael addition of the enol to the corresponding enone to give after further dehydration and lactonisation coumalic acid (Scheme 10). Returning to the main discussion, a recent synthesis of rosiglitazone [41] exemplifies the advantages of employing resin-bound agents in order to increase
- ) resulting in the formation of enone 2.23, this material was subsequently condensed with enamide 2.22 to directly yield clevidipine (2.3, Route B, [71]). A final strategy is depicted in Scheme 26 (Route C, [72]). This approach is similar to route B, however, it introduces the amine as part of the readily
Gold(I)-catalyzed enantioselective cycloaddition reactions
Beilstein J. Org. Chem. 2013, 9, 2250–2264, doi:10.3762/bjoc.9.264
- core of frondosins (for example, 5a), in 68% yield and 90% ee (Scheme 4). Since this bicyclic enone was previously elaborated into frondosin A and B, the approach represented a streamlined formal enantioselective synthesis of both molecules. Analogous to other transition metals from groups eight to
Elucidation of the regio- and chemoselectivity of enzymatic allylic oxidations with Pleurotus sapidus – conversion of selected spirocyclic terpenoids and computational analysis
Beilstein J. Org. Chem. 2013, 9, 2233–2241, doi:10.3762/bjoc.9.262
- clean and gives the enone 2 in good yield along with minor amounts of the corresponding allyl alcohol 3 and the epoxide 4a. This successful conversion of theaspirane (1) encouraged us to investigate the oxidation of other spirocyclic terpenoids. Many oxidized spiroethers are valuable flavor compounds or
- oxidation of allyl ether 7 may follow two alternative pathways either to the α,β-unsaturated lactone 14 or to the enone 15 (allylic oxidations at exocyclic positions are generally less favorable if radical mechanisms are operating) [35]. Due to sterical hindrance at position 5 and the strong activation for
- should thus be privileged for oxidation. As a consequence, the α,β-unsaturated lactone 17 is indeed the major product along with some unidentified more complex oxidation products. Again, oxidation in 5-position of 11 to the enone 18 was not observed. In addition, the allylic hydrogens in 9-position are
Regioselective 1,4-trifluoromethylation of α,β-unsaturated ketones via a S-(trifluoromethyl)diphenylsulfonium salts/copper system
Beilstein J. Org. Chem. 2013, 9, 2189–2193, doi:10.3762/bjoc.9.257
- –Hillman adducts (via SN2’ [16] or successive SN2’/SN2’ mode [17]). Sevenard and co-workers reported the nucleophilic 1,4-trifluoromethylation to chromones, coumarins and cyclohex-2-enone using the Ruppert–Prakash reagent, which was achieved by blocking the carbonyl moiety of the substrates with a bulky
- , aromatic rings substituted with either electron-donating or -withdrawing substituents, such as methyl, methoxy, fluoro and chloro were tolerated (Table 2, entries 2–4). A heteroaromatic, furanyl-substituted enone was compatible with the same reaction conditions (Table 2, entry 6). We next examined
- -substituted enone also produced the desired product 2l (Table 2, entry 12). Based on these results, we hypothesized the reaction mechanism as shown in Scheme 2. First, the conjugate trifluoromethylation of α,β-unsaturated ketones would be initiated by a single-electron transfer between S-(trifluoromethyl
A concise enantioselective synthesis of the guaiane sesquiterpene (−)-oxyphyllol
Beilstein J. Org. Chem. 2013, 9, 2028–2032, doi:10.3762/bjoc.9.239
- Martin Zahel Peter Metz Fachrichtung Chemie und Lebensmittelchemie, Organische Chemie I, Technische Universität Dresden, Bergstrasse 66, 01069 Dresden, Germany 10.3762/bjoc.9.239 Abstract (−)-Oxyphyllol was prepared in only 4 steps from an epoxy enone that already served as an intermediate for
- 3 can be utilized to generate the isopropyl group, and a regioselective transannular epoxide opening would construct the oxygen-bridged bicyclic hydroazulene framework. Alcohol 3 was traced back to the known epoxy enone 4 that already served as an intermediate for the total synthesis of 5 [6]. As
The chemistry of amine radical cations produced by visible light photoredox catalysis
Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234
- found to be optimal, lie within a narrow range of pKa values. The authors suggested that TFA protonates the enone 83, thus accelerating the addition of the α-amino radical to the enone (84). The Nishibayashi group reported that α-amino radicals generated from a different class of amines, anilines 87
Gold-catalyzed regioselective oxidation of propargylic carboxylates: a reliable access to α-carboxy-α,β-unsaturated ketones/aldehydes
Beilstein J. Org. Chem. 2013, 9, 1925–1930, doi:10.3762/bjoc.9.227
- the use of a P,S-bidentate ligand, which is proposed to enable the formation of tris-coordinated and hence less electrophilic gold carbene species. α-Carboxy α,β-unsaturated ketones/aldehydes can be obtained with fair to excellent yields. Keywords: enone; gold catalysis; oxidation; propargyl
- proceeded efficiently, yielding the α-acetoxyenone 5a-OAc (Z/E >50:1) and the isomeric β-acetoxyenone 5a-H in an excellent combined 92% yield along with a minute amount of the enone 6 (<0.5%, Scheme 3); moreover, 5a-OAc is favored over 5a-H by a ratio of ~7:1. Of particular importance is that the
- hydrolysis, only under thermal and anhydrous conditions products derived from the latter processes can be predominantly formed [32]; under our conditions (at ambient temperature and without exclusion of moisture), the enone 6 was indeed detected but in a minute amount, suggesting that the 1,2-acyloxy
A reductive coupling strategy towards ripostatin A
Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175
- ]. Treatment of 20 with the sulfur ylide derived from trimethylsulfoxonium iodide [33][34] led to recovery of starting material at room temperature, but decomposition at elevated temperatures. Instead, the enone was smoothly reduced to the allylic alcohol, and a Furukawa-modified Simmons–Smith reaction [35
- around the enone. Aliphatic enones react more sluggishly in this transformation; however, 3,4,5-trimethoxyphenylboronic acid may be used as a more efficient nucleophilic partner to circumvent this limitation. Application of this transformation to the ripostatin A epoxide fragment 5 allows installation of
- the C13 hydroxy group via conjugate addition to the δ-hydroxy-α,β-enone 49 (Figure 5). Although the diastereoselectivity of this reaction using substrates with a chiral center at the hydroxy group had not been investigated in the published study, substitution at the carbinol position was reportedly
Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives via radical pathways
Beilstein J. Org. Chem. 2013, 9, 1397–1406, doi:10.3762/bjoc.9.156
- Scheme 3) [22][24][27]. On the other hand, the same spirocyclic ketone is obtained in the 9,10-dicyanoanthracene (DCA) and biphenyl (BP) sensitized PET reaction of probe II, while reactions of this substrate with certain oxidants afford ring-expanded ketone and enone products (right in Scheme 3) [23][25
- presence of Cu(OAc)2 [25]. Only a trace amount of ring-expanded enone 4 along with small amounts of desilylated alcohol 1b (ca. 8%) and ketone 5 were detected in the product mixture by using 1H NMR analysis. Treatment of 1a (0.19 mmol) with n-Bu4NF (2.0 equiv) in THF for 1 h followed by hydrolysis gave a
- summarized in Table 1. As expected, this process produces ketone 3 as the major product along with both 2 and ring-expanded enone 4 as minor products. Moreover, the order of addition of 1b and Cu(OAc)2 does not significantly affect the product distribution (compare Table 1, entry 1 to entry 2). An
Establishing the concept of aza-[3 + 3] annulations using enones as a key expansion of this unified strategy in alkaloid synthesis
Beilstein J. Org. Chem. 2013, 9, 1170–1178, doi:10.3762/bjoc.9.131
- Aleksey I. Gerasyuto Zhi-Xiong Ma Grant S. Buchanan Richard P. Hsung Division of Pharmaceutical Sciences, School of Pharmacy, and Department of Chemistry, University of Wisconsin, Madison, WI 53705, USA 10.3762/bjoc.9.131 Abstract A successful enone version of an intramolecular aza-[3 + 3
- expand the scope of the enone aza-[3 + 3] annulation was made in the form of propyleine synthesis as a proof of concept. While synthesis of the enone annulation precursor was successfully accomplished, the annulation proved to be challenging and was only modestly successful. Keywords: alkaloids
- ][63], and tubulosine [64]. With the appropriate choice of an R group in the synthetic design, a highly convergent and expedient strategy can come forth for constructing these alkaloids. We report herein our success in achieving intramolecular aza-[3 + 3] annulations of an enone. Results and Discussion
Synthesis of the tetracyclic core of Illicium sesquiterpenes using an organocatalyzed asymmetric Robinson annulation
Beilstein J. Org. Chem. 2013, 9, 1135–1140, doi:10.3762/bjoc.9.126
- enantioselectivity and short reaction time, we decided to pursue this conversion at 40 °C where we obtained an enantiomeric excess of 90% (70% yield after 14 days). The enantiomerically enriched Hajos–Wiechert-like diketone 8 (ee > 90%) was then subjected to a selective protection of the C-6 enone motif to yield
- enone 10 (>10 grams) for further functionalization. Conversion of 10 to 9 was accomplished based on our previously reported strategy (Scheme 3) [25]. Treatment of 10 with magnesium methyl carbonate (MMC) [79][80][81] yielded the C-5 carboxylic acid that, without further purification, was esterified
- (0)-catalyzed carbomethoxylation [87][88][89][90] produced the desired C-ring lactone 20 in 61% yield. Epoxidation of the C-6/C-7 enone with NaOH/H2O2 followed by oxidative cleavage of the C-11 terminal alkene under OsO4/NaIO4 conditions [91][92] afforded the corresponding C-11 aldehyde. Exposure of
Formal synthesis of (−)-agelastatin A: an iron(II)-mediated cyclization strategy
Beilstein J. Org. Chem. 2013, 9, 860–865, doi:10.3762/bjoc.9.99
- (1.5 equiv) in EtOH effected cyclization, but the yield of 5a was poor due to the concomitant formation of carbamate 9 (39%) and enone 10 (30%) (Table 1, entry 1). This was in marked contrast to the observation that the same reagent system, i.e., FeBr2 (0.5 equiv)/Bu4NBr (1.2 equiv), allowed the
- provided evidence that these byproducts were generated by the intramolecular cyclization of enone 10 with TMSCl in EtOH, suggesting that the FeCl2/TMSCl system also gave enone 10 in ca. 30% yield [37]. The present study on the aminohalogenation reaction of carbamate 8 has inspired mechanistic insights that
- deserve discussion (Scheme 4). We hypothesize that cyclized material 5a/5b, reduced material 9, and enone 10 are generated from an N–iron complex (i) that has free-radical character, as previously proposed in the catalytic cyclization of azidoformates [30][38][39][40]. The contrasting yields obtained from
Some aspects of radical chemistry in the assembly of complex molecular architectures
Beilstein J. Org. Chem. 2013, 9, 557–576, doi:10.3762/bjoc.9.61
- by the preparation of enone 81 from allylic alcohol 80 in Scheme 17. By varying the xanthate partner, different substitution patterns and rings may then be introduced. Two examples, 83 and 86, in Scheme 17 illustrate the formation of triquinanes via bicyclic intermediate xanthates 82 and 85. The
- ]. In the sequence displayed in Scheme 18, the addition–cyclisation of a malonyl radical to enyne 89 furnishes allenyl acetate 91 by cyclisation of propargyl radical 90 [41]. Compound 91 readily undergoes reductive dexanthylation and solvolysis into enone 92, and internal Michael addition to give
Efficient synthesis of β’-amino-α,β-unsaturated ketones
Beilstein J. Org. Chem. 2013, 9, 486–495, doi:10.3762/bjoc.9.52
- ester moiety to a Weinreb amide [18] followed by changing the nitrogen protecting group to a carbamate furnished the key intermediate 6, which could be further alkylated with Grignard reagents to give β’-amino protected α,β-enone 1 in good overall yield and high enantiomeric excess. As Grignard reagents
Metal-mediated aminocatalysis provides mild conditions: Enantioselective Michael addition mediated by primary amino catalysts and alkali-metal ions
Beilstein J. Org. Chem. 2013, 9, 155–165, doi:10.3762/bjoc.9.18
- the primary amino group. The most promising counter ions are expected to be from the first group of the periodic table of elements, and test reactions were carried out by employing catalyst 5 and 7 with benzylideneacetone (9) and cyclohex-2-enone (10) (Figure 2) as substrates (Table 1). It was found
- % whereas the trans-diaminocyclohexane derivatives could only reach up to 47% ee (Table 1, entry 5). There is a strong preference for 7 to produce higher ee’s if cyclic enones are used, whereas diaminocyclohexane derivatives perform better with the acyclic trans-enone 9 (Table 1, entry 4 versus Table 2
Flow photochemistry: Old light through new windows
Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229
- ) [26]. Asymmetric induction can be achieved in [2 + 2] cycloadditions through the use of a chiral auxilliary. The [2 + 2] reaction shown in Scheme 3 employed a chiral ester function to direct the facial selectivity of the addition of the enone to cyclopentene. Diastereoselectivity was found to be
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