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Search for "ylide" in Full Text gives 145 result(s) in Beilstein Journal of Organic Chemistry.
Ring-closing-metathesis-based synthesis of annellated coumarins from 8-allylcoumarins
Beilstein J. Org. Chem. 2018, 14, 2991–2998, doi:10.3762/bjoc.14.278
- the past few years. Starting materials are allyl ethers of salicylic aldehydes or ketones 5 and the stable ylide ethyl (triphosphoranylidene)acetate (6), which upon microwave irradiation undergo a tandem Claisen rearrangement/Wittig olefination/cyclization sequence. This sequence was pioneered by the
One-pot synthesis of epoxides from benzyl alcohols and aldehydes
Beilstein J. Org. Chem. 2018, 14, 2308–2312, doi:10.3762/bjoc.14.205
- alcohols and aldehydes. Keywords: Corey–Chaykovsky; epoxide; heterocycle; one-pot; ylide; Introduction Epoxides have historically served as strategic functional groups in target-oriented synthesis [1][2][3][4]. Common examples of their utility include stereospecific ring opening [5][6][7], rearrangements
An efficient and facile access to highly functionalized pyrrole derivatives
Beilstein J. Org. Chem. 2018, 14, 884–890, doi:10.3762/bjoc.14.75
- , azomethine ylide) as the key substrate for 1,3-dipolar cycloadditions, the reaction conditions were very different exemplified by the wide range of reaction times from 0.3 h to 120 h, and the variable yields from 68% to 100% in different solvents. In order to establish the optimal experimental conditions
- suitable for the one-pot synthesis of pyrrolo[3,4-c]pyrrole-1,3-diones 12a–k, we investigated the reaction conditions step by step. Initially, benzaldehyde (7a) and ethyl glycinate hydrochloride (8a) were chosen as the model substrates for obtaining azomethine ylide 9a, and the results are summarized in
- Table 1. Based on reported methods, Et3N as base, MgSO4 as desiccant and CH2Cl2 as solvent were used for the synthesis of the azomethine ylide [13][14][17][18][19][20][21][22][23][24]. Because 9a easily decomposed to benzaldehyde on silica gel when monitored by TLC, we used 1H NMR to monitor the
Liquid-assisted grinding and ion pairing regulates percentage conversion and diastereoselectivity of the Wittig reaction under mechanochemical conditions
Beilstein J. Org. Chem. 2018, 14, 688–696, doi:10.3762/bjoc.14.57
- , and 5 indicates that the carbonate bases deprotonated the phosphonium salt to form the ylide which then subsequently added to the benzaldehyde. However, the oxygen anion could not bind to the phosphorus cation to produce the stilbene product, presumably due to the mismatched counter ion pair. After
One-pot sequential synthesis of tetrasubstituted thiophenes via sulfur ylide-like intermediates
Beilstein J. Org. Chem. 2018, 14, 243–252, doi:10.3762/bjoc.14.16
- facile preparation of thienyl heterocycles 8. The mechanism for this reaction is based on the formation of a sulfur ylide-like intermediate. It was clearly suggested by (i) the intramolecular cyclization of ketene N,S-acetals 7 to the corresponding thiophenes 8, (ii) 1H NMR studies of Meldrum’s acid
- -substituted aminothioacetals 9, and (iii) substitution studies of the methoxy group on Meldrum’s acid containing N,S-acetals 9b. Notably, in terms of structural effects on the reactivity and stability of sulfur ylide-like intermediates, 2-pyridyl substituted compound 7a exhibited superior properties over
- those of others. Keywords: 5-(heterocyclic)thiophenes; one-pot sequential synthesis; sulfur ylide; tetrasubstituted thiophene; Introduction Since the discovery of stable sulfonium ylides 1 in 1930 [1] and the pioneering work of several research groups during the 1960s (2 and 3) [2][3][4][5][6][7][8][9
Progress in copper-catalyzed trifluoromethylation
Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11
- halides with traditional trifluoromethylation reagents and a trifluoromethyl-substituted sulfonium ylide as a new reagent The CuI-mediated cross-coupling protocol using TESCF3 was firstly reported by Urata and Fuchikami [11]. The proposed mechanism of this reaction was demonstrated in Scheme 1. But it was
- reagent, trifluoromethyl-substituted sulfonium ylide, which was prepared by a Rh-catalyzed carbenoid addition to trifluoromethyl thioether (Scheme 4). This process was conducted in dichloromethane at 40 °C for 4 h with a catalyst loading of 100 ppm. Moreover, this new reagent was easily scaled-up and
- producing byproducts from a pentafluoroethylation. The proposed reaction mechanism is depicted in Scheme 9. First, a phosphonium ylide is formed after treating DFPB with DBU, and then dissociated to generate a difluorocarbene. The difluorocarbene reacts with DBU affording nitrogen ylide I, followed by a
Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis
Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269
- to vinylphosphonium salt. A phosphorus ylide thus generated undergoes a subsequent intramolecular Wittig reaction, leading to a carbo- or heterocyclic ring closure (Scheme 2) [1][2][3]. This reaction can be considered as a general method for the synthesis of carbo- and heterocyclic systems
- triphenylphosphine with 1-bromoethylbenzene. The resulting phosphonium salt 11 was then deprotonated to the corresponding ylide 12, which in the last step was subjected to bromination to give the expected α-bromoethylphosphonium bromide 13 [10]. 1.3. Peterson olefination of α-trimethylsilylphosphonium ylides with
- at room temperature to give the corresponding α-trimethylsilylphosphonium salt 14. The latter salt was deprotonated in the presence of s-BuLi under kinetically controlled conditions, and the resulting ylide 15 reacted with aldehyde, providing tributylvinylphosphonium salt derivatives 17 in good
Rh(II)-mediated domino [4 + 1]-annulation of α-cyanothioacetamides using diazoesters: A new entry for the synthesis of multisubstituted thiophenes
Beilstein J. Org. Chem. 2017, 13, 2569–2576, doi:10.3762/bjoc.13.253
- ’, as illustrated in Scheme 4. Initially generated from diazoester 2 carbenoid A attacks the sulfur atom of thioamide 1 to give the key intermediate S-ylide B [36][37][38][59][60], which is stabilized by ‘thioamide resonance’ [36][37][38]. The anion center of S-ylide B then attacks the carbon atom of
- or 5. Principally, thiophenes 3 and 5 could be derived from the S-ylide B in a somewhat different way, as for instance: coordination E of cyano group in S-ylide with a rhodium catalyst [63] gives rise to zwitterion F with a negative charge located on the rhodium atom, followed by recovery of the
- ylide with the rhodium catalyst. Within the adopted general scheme, the occurrence of thiophenes 4 could be rationalized by partial hydrolysis of carbamates 3 under the reaction conditions with the initial formation of the primary heteroaromatic amines 7. The latter then interact with carbenoids A, to
Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies
Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221
- . In contrast to the nucleophilic dimethoxycarbene, the formal transfer of the bis(carbomethoxy)carbene from the sulfur ylide 12 to E-1a leads to the cyclopropane derivative 13 [23] (Scheme 4). The reaction was proposed to occur stepwise via the zwiterrionic intermediate 14. Another example of a
- - and Z-1b, and depending on the substitution pattern of the aziridine ring, the formation of the pyrrolidine derivative 34 occurred either with complete stereoselectivity or mixtures of isomeric products were obtained. The [3 + 2]-cycloaddition of the azomethine ylide E,Z-32a, formed via conrotatory
- mixture of products was obtained starting from trans-33b. The formation of these isomeric products suggests that in the course of the reaction, isomerizations of both the intermediate azomethine ylide of type 32 as well as of the electron-deficient dipolarophiles E- and Z-1b, occur. The observed
Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective
Beilstein J. Org. Chem. 2017, 13, 2214–2234, doi:10.3762/bjoc.13.220
- ) followed by a formal [4 + 1]-annulation reaction with ylide (tandem Michael addition/intramolecular nucleophilic substitution of dimethylsulfide by oximate anion in intermediate 94). The addition of sulfonium ylides to nitrosoalkenes can end up not only with cyclic products, but also with α,β-unsaturated
- oximes 95, if the elimination of dimethyl sulfide from 94 proceeds faster than the cyclization. The cyclization/elimination selectivity was found be highly dependent on the nature of substituents in ylide 92. Only when R3 was an acyl or phenacyl group, exclusive formation of isoxazoline products 93 was
Mechanochemical synthesis of small organic molecules
Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186
- Reaction Pecharsky and co-workers reported the solvent-free mechanochemical synthesis of phosphonium salts [54] and phosphorus ylides [55] in the presence of the weak base K2CO3. Mechanochemically prepared phosphorous ylide from triphenylphosphine in presence of K2CO3 was utilized for a one-pot solvent
Dimerization reactions of aryl selenophen-2-yl-substituted thiocarbonyl S-methanides as diradical processes: a computational study
Beilstein J. Org. Chem. 2017, 13, 410–416, doi:10.3762/bjoc.13.44
- . This reaction has a free energy of the transition state of 15.7 kcal/mol (TS1) and is spontaneous by −35.5 kcal/mol (Figure 2). In an alternative reaction, two molecules of thiocarbonyl ylide 8 initially form a complex 15, which is bound by 4.5 kcal/mol (∆H (THF, 298 K)) and subsequently converts over
- Supporting Information File 1). The cyclization of the diradical leading to 2,2-diphenylthiirane occurs via a transition state with a free energy barrier very similar to the conversion 8 → 3a (16.4 versus 15.7 kcal/mol, respectively). The intermediate complex of two ylide molecules converts into the 1,6
Multicomponent synthesis of spiropyrrolidine analogues derived from vinylindole/indazole by a 1,3-dipolar cycloaddition reaction
Beilstein J. Org. Chem. 2016, 12, 2893–2897, doi:10.3762/bjoc.12.288
- out by reacting N-alkylvinyl products 3 with azomethine ylide, generated in situ through decarboxylative condensation of ninhydrin (4) and sarcosine (5). The 1,3-dipolar cycloaddition of the ylide with the olefin 3 yielded spiropyrrolidines 7 with regiospecificity (Table 1, entries 1–4). The formation
- of the azomethine ylide intermediate and a plausible reaction pathway for the formation of the spiranes is depicted following the retrosynthetic strategy in Scheme 2. The applicability of the cycloaddition reaction was explored first for indole derivatives 7a–d and then extended to the synthesis of
From betaines to anionic N-heterocyclic carbenes. Borane, gold, rhodium, and nickel complexes starting from an imidazoliumphenolate and its carbene tautomer
Beilstein J. Org. Chem. 2016, 12, 2673–2681, doi:10.3762/bjoc.12.264
- been prepared from mesoionic compounds (Figure 1). The carbenes 3 [31] and 4 [32][33] originate from a conjugated ylide and a cross-conjugated mesomeric betaine, respectively. A review elucidates the interconversions of mesomeric betaines to different types of N-heterocyclic carbenes (NHC, aNHC, rNHC
Catalytic Wittig and aza-Wittig reactions
Beilstein J. Org. Chem. 2016, 12, 2577–2587, doi:10.3762/bjoc.12.253
- inexpensive reagents to generate the necessary phosphonium ylide (phosphorane) reactant (a phosphine, typically Ph3P (1), an alkyl halide and a base), also adds to its appeal [3][4]. However, despite its proven utility, the Wittig reaction suffers from limitations that may deter from its use, especially on a
- developed the first reported catalytic Wittig-type reactions in which Bu3As (3, 0.2 equivalents) was used as the catalyst (Scheme 2) [9][10]. The reaction of 3 with an alkyl halide 4 followed by deprotonation using potassium carbonate generated the corresponding arsonium ylide (5) which, in turn, reacted
- )porphyrinate), and ethyl diazoacetate (11) to generate arsonium ylide 12 for use in biphasic catalytic Wittig-type reactions (Scheme 3) [11]. In these reactions sodium hydrosulfite replaced triphenylphosphite as the reducing reagent to convert the byproduct Ph3As=O (13) back into 9 in the aqueous phase of the
Sydnone C-4 heteroarylation with an indolizine ring via Chichibabin indolizine synthesis
Beilstein J. Org. Chem. 2016, 12, 2503–2510, doi:10.3762/bjoc.12.245
- ; Chichibabin synthesis; indolizine; pyridinium N-ylide; sydnone; Introduction In recent decades, interest in the syntheses of biheteroaryls has been focused on the creation of new hetaryl–hetaryl C(sp2)–C(sp2) bonds, in particular through cross-coupling reactions. These reactions are catalyzed by palladium or
- products 12a–c with yields in the range of 41–52%. Bearing in mind that the formation of indolizines through Chichibabin synthesis and 1,3-dipolar cycloaddition reaction requires in both cases the formation of an intermediate pyridinium N-ylide, it is expected that in these cycloadditions a mixture of
An effective one-pot access to polynuclear dispiroheterocyclic structures comprising pyrrolidinyloxindole and imidazothiazolotriazine moieties via a 1,3-dipolar cycloaddition strategy
Beilstein J. Org. Chem. 2016, 12, 2240–2249, doi:10.3762/bjoc.12.216
- combined the imidazothiazolotriazine and 3,3’-spiropyrrolidinyloxindole moieties by a 1,3-dipolar cycloaddition of an azomethine ylide generated in situ from paraformaldehyde and sarcosine to oxoindolylidene derivatives of imidazothiazolotriazine. During this work we have found that the “small” azomethine
- ylide generated from paraformaldehyde and sarcosine approaches the double bond plane in (oxoindolylidene)imidazothiazolotriazines mainly from the side of the imidazolidine ring opposite to the phenyl groups (syn attack) (Scheme 1) [5]. To further expand the spectrum of biological activity, it is of
- for the generation of the azomethine ylide as well as for nitrobenzylidene derivative 1b as dipolarophile. To further extend the substrate scope of this reaction, we used benzylidene derivatives of other imidazothiazolotriazines 1d–f without substituents at the bridge carbon atoms C(3a) and C(9a). The
Stereoselective synthesis of fused tetrahydroquinazolines through one-pot double [3 + 2] dipolar cycloadditions followed by [5 + 1] annulation
Beilstein J. Org. Chem. 2016, 12, 2204–2210, doi:10.3762/bjoc.12.211
- , NH 03435, USA 10.3762/bjoc.12.211 Abstract The one-pot [3 + 2] cycloaddition of an azomethine ylide with a maleimide followed by another [3 + 2] cycloaddition of an azide with the second maleimide gives a 1,5-diamino intermediate which is used for a sequential aminomethylation reaction with
- using one-pot intermolecular or intramolecular [3 + 2] azomethine ylide cycloadditions [22][23][24][25][26][27] as the initial step followed by cyclization or cycloaddition reactions to form polycyclic scaffolds with skeleton, substitution, and stereochemistry diversities. Introduced in this paper is a
- of azomethine ylide was carried out using glycine methyl ester (3a), 2-azidobenzaldehyde (4a), and N-methylmaleimide (5a) as reactants [33]. After exploring the reactions with different temperatures, times, solvents, and bases, it was found that with a 1.2:1.1:1.0 ratio of 3a:4a:5a, Et3N as a base
Unusual reactions of diazocarbonyl compounds with α,β-unsaturated δ-amino esters: Rh(II)-catalyzed Wolff rearrangement and oxidative cleavage of N–H-insertion products
Beilstein J. Org. Chem. 2016, 12, 1904–1910, doi:10.3762/bjoc.12.180
- appearance of the amides 4 and 7 during the processes studied (Scheme 3). At first, upon catalytic decomposition of diazocarbonyl compounds 2a–c and 3c, N-ylide E is generated, stabilization of which by proton transfer produces an ordinary N–H-insertion product, α-ketoamine F. Similar reactions are well
Synthesis of ferrocenyl-substituted 1,3-dithiolanes via [3 + 2]-cycloadditions of ferrocenyl hetaryl thioketones with thiocarbonyl S-methanides
Beilstein J. Org. Chem. 2016, 12, 1421–1427, doi:10.3762/bjoc.12.136
- 1,5-diradical as a key intermediate. The complete change of the reaction mechanism toward the concerted [3 + 2]-cycloaddition was observed in the reaction of a sterically crowded cycloaliphatic thiocarbonyl ylide with ferrocenyl methyl thioketone. Keywords: [3 + 2]-cycloadditions; 1,3-dithiolanes
Synthesis of a deuterated probe for the confocal Raman microscopy imaging of squalenoyl nanomedicines
Beilstein J. Org. Chem. 2016, 12, 1127–1135, doi:10.3762/bjoc.12.109
- -bromopropane-d7 (8) with triphenylphosphine [29]. To our surprise, condensation of dialdehyde 5 with one equivalent of the ylide 4 (9, n-BuLi, THF, −78 °C) did not afford any amount of the desired deuterated olefin but only polar material that could not be characterized. In an attempt to find more efficient
- reaction conditions, we investigated this reaction using the simple aldehyde 10 as a model compound, easily accessible from squalene according to the van Tamelen procedure [30]. The condensation of ylide 4 with 10 seemed to be an easy task, but many well-established procedures using various bases (n-BuLi
- , LiHMDS, NaH/DMSO, PhLi) [29][31][32] gave only intractable materials. We finally found that the treatment of 10 with the “instant ylide mixture” of Schlosser made by grinding a solid mixture of 9 and NaNH2 [33] delivered the desired squalene-d6 (11) although in a low 18% yield. However, when applied to
Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(−)-myrtenol nitrate
Beilstein J. Org. Chem. 2016, 12, 1081–1095, doi:10.3762/bjoc.12.103
- , the synthesis of either (E)-3-methyl-4-chlorobut-2-en-1-ol ((E)-60) or (Z)-3-methyl-4-chlorobut-2-en-1-ol ((Z)-61, Scheme 8). Reacting triphenylphosphine with 1-((2-bromoethoxy)methyl)-4-methoxybenzene (55) generated non-stabilized phosphonium ylide (2-(4-methoxybenzyloxy)ethyl)triphenylphosphonium
- ester via a Horner–Wadsworth–Emmons reaction caught our attention [47]. Changing tack and in a slightly modified procedure to that originally reported by Fujiwara et al. triethyl phosphonoacetate was deprotonated (NaH) and the resulting stabilised ylide (not shown) reacted by slow addition of
- of mercury(I) chloride (0.06 mol %) and sulfuric acid (0.35 mol %) in water following the procedure of Boger et al. [51]. 63 was afforded in an unoptimized 78% yield. Employing the conditions outlined in Scheme 10 63 reacted with the stabilized ylide generated from the deprotonation of triethyl
One-pot synthesis of enantiomerically pure N-protected allylic amines from N-protected α-amino esters
Beilstein J. Org. Chem. 2016, 12, 957–962, doi:10.3762/bjoc.12.94
- ]. However, that preliminary study was limited to the use of phosphonium ylide reagents and commonly t-Boc (iBoc and Ac were used once) as N-protecting group. To the best of our knowledge, no further studies on the reaction conditions have been carried out. Instead, the method was applied to N-Ac aspartic
- Discussion The experimental procedure for the tandem reduction–Wittig olefination synthesis of allylic amines reported the use of toluene as solvent for the reduction step and THF as solvent to prepare the phosphonium ylide [17]. Consequently, the Wittig olefination takes place in a 2:1 (toluene/THF) solvent
- as starting material (S)-methyl 2-(dibenzylamino)propanoate (1) [22]. In order to avoid the stereochemical drawback of the Wittig olefination (i.e., mixture of E and Z isomers), we selected the stabilized ylide ethyl 2-(triphenylphosphoranylidene)acetate, which gives the E isomer [23]. The results
Enantioselective carbenoid insertion into C(sp3)–H bonds
Beilstein J. Org. Chem. 2016, 12, 882–902, doi:10.3762/bjoc.12.87
- (Table 3) [9]. This work is particularly important because, at that time, the carbenoids derived from rhodium complexes were the most used for insertion reactions in C(sp3)–H bonds. Comparing the results of Table 3, the same enantiomer was obtained mainly for both carbenoid precursors, ylide 42a and the
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
- muraymycin core structure (Scheme 6) [78][99]. The key step of their route was a sulfur-ylide reaction with high substrate-controlled diastereoselectivity [100][101][102]. This epoxide-forming sulfur-ylide reaction had been established before by Sarabia et al. [103][104]. After some initial confusion
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