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Search for "olefination" in Full Text gives 138 result(s) in Beilstein Journal of Organic Chemistry.
One hundred years of benzotropone chemistry
Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98
- : Fulvalenes are typical cross-conjugated carbocyclic unsaturated compounds and are of theoretical and synthetic interest [59]. Several researchers have studied the synthesis of benzofulvalenes via the carbonyl group of 4,5-benzotropone (11) (Scheme 11). Halton’s group applied the Peterson olefination reaction
Preparation, structure, and reactivity of bicyclic benziodazole: a new hypervalent iodine heterocycle
Beilstein J. Org. Chem. 2018, 14, 1016–1020, doi:10.3762/bjoc.14.87
- example, azidobenziodazole was used as an efficient azidation reagent with a reactivity similar to azidobenziodoxoles [33]. Recently, the Wang group reported a rhenium catalyst-mediated oxidative dehydrogenative olefination of a C(sp3)–H bond using acetoxybenziodazole reagents [36]. To the best of our
A stereoselective and flexible synthesis to access both enantiomers of N-acetylgalactosamine and peracetylated N-acetylidosamine
Beilstein J. Org. Chem. 2018, 14, 856–860, doi:10.3762/bjoc.14.71
- as starting material reduces the flexibility of this approach. Another strategy introduces the nitrogen at C-2 [11] via the 2-iodoxybenzoic acid-mediated generation of an oxazolidinone ring, selectively leading to C2–C3 syn-products [12]. A third approach features E-selective Julia olefination of (R
Bromide-assisted chemoselective Heck reaction of 3-bromoindazoles under high-speed ball-milling conditions: synthesis of axitinib
Beilstein J. Org. Chem. 2018, 14, 786–795, doi:10.3762/bjoc.14.66
- TBAB [24][25][26][27]. However, for inert and liable to dehalogenation bromo-heteroarenes, no desired response had been obtained yet. Thus, this work was going to establish a mild and chemoselective olefination of 3-bromoindazoles under ball-milling conditions (Scheme 2). Results and Discussion
- = 6 mm, ФMB = 0.293), 500 rpm, 45 min. Optimisation of the reaction conditions for the olefination of 3-bromoindazoles.a Examination of the influence of the grinding auxiliary on the reaction outcomea. Supporting Information Supporting Information File 108: Reaction optimization studies, details of
Electrochemical Corey–Winter reaction. Reduction of thiocarbonates in aqueous methanol media and application to the synthesis of a naturally occurring α-pyrone
Beilstein J. Org. Chem. 2018, 14, 547–552, doi:10.3762/bjoc.14.41
- ; thiocarbonates; Findings The Corey–Winter reaction (also known as the Corey–Winter reductive olefination) is a chemical transformation that permits the conversion of 1,2-diols A into E-alkenes C via the formation and reduction of a cyclic thiocarbonate intermediate B (Scheme 1) [1][2]. In general this reaction
- aspects of the reaction that are currently under study to generate a robust and general olefination electrochemical method via the thiocarbonate reduction; nevertheless, this letter shows for the first time the potential use of electrochemistry with this functional group using green reduction conditions
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
- 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
- aldehydes An interesting alternative pathway to vinylphosphonium salts, based on a Peterson-like olefination of α-trimethylsilyl phosphonium ylides 15, was described by McNulty and Das and by Łukaszewicz et al. The commercially readily available iodomethyltrimethylsilane was reacted with tributylphosphine
- yields via Peterson olefination through a silylated betaine 16. The alternatively possible Wittig reaction to vinylsilane 18 can be considered as a side reaction (Scheme 11) [17][18]. The transformation shown in Scheme 11 was proven to be a general reaction with the possible participation of both
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
- Analogues in which there is no side chain or where the side chain stereochemistry is not controlled Gly-ψ[CF=CH]-Gly The Gly-ψ[CF=CH]-Gly analogue is the simplest one, as it does not present side chains. Its synthesis was performed by two groups, using in both cases an olefination reaction. Sano’s group was
- interested in the Horner–Wadsworth–Emmons (HWE) olefination to develop the synthesis of α-fluoro-α,β-unsaturated ester 3, which can be used as a precursor for the synthesis of monofluoroalkene-based dipeptide isosteres [23]. Cbz-Gly-ψ[(Z)-CF=CH]-Gly 5 was obtained in seven steps (Scheme 1). First, triethyl 2
- -fluoro-2-phosphonoacetate (1) was converted into the α-fluoro-α,β-unsaturated carbonyl 3 using the HWE olefination. The (Z)-isomer was obtained with complete selectivity. Then, reduction of the ester into the corresponding alcohol followed by a Mitsunobu reaction allowed the insertion of the NH
Homologated amino acids with three vicinal fluorines positioned along the backbone: development of a stereoselective synthesis
Beilstein J. Org. Chem. 2017, 13, 2316–2325, doi:10.3762/bjoc.13.228
- ]. Therefore we turned our attention to converting the fluorinated aldehyde 8b (Scheme 1) into the allylic fluoride 16. The crude fluorinated aldehyde 8b was treated with a variety of olefination reagents (e.g., Tebbe; Wittig; reagent 15 [27]). Unfortunately, however, the desired allylic fluoride 16 was either
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
- intermediate 45, which was subjected to Wittig olefination. Subsequent aza-Sakurai cyclization of intermediate 46 provided tricyclic derivative 47 as a single stereoisomer, which was then transformed into target myrioneurinol by standard operations. Addition of organometallic reagents to conjugated
Synthesis of 2-aminosuberic acid derivatives as components of some histone deacetylase inhibiting cyclic tetrapeptides
Beilstein J. Org. Chem. 2017, 13, 2153–2156, doi:10.3762/bjoc.13.214
- conventional steps viz. HWE-type olefination leading to the unsaturated ester 5, saturation of the double bond in the latter to 6, reduction of the ester moiety in 6 to the alcohol 7 followed by its oxidation. The aldehyde 8 thus obtained was subjected to a Wittig olefination to obtain the desired alkene 9 in
A novel application of 2-silylated 1,3-dithiolanes for the synthesis of aryl/hetaryl-substituted ethenes and dibenzofulvenes
Beilstein J. Org. Chem. 2017, 13, 1900–1906, doi:10.3762/bjoc.13.185
- presented protocol offers a new, highly efficient approach to tetrasubstituted ethenes and dibenzofulvenes bearing aryl and/or hetaryl substituents. Keywords: diazomethanes; 1,3-dipolar cycloadditions; olefination reactions; reaction mechanisms; thioketones; Introduction Aryl and hetaryl-substituted
- . The development of methods for the synthesis of substituted ethenes is of great importance and the so-called olefination reactions allow for valuable functional-group transformations [10][11][12][13]. As a general method for the preparation of tetrasubstituted ethenes, the McMurry reaction is widely
- useful olefination reactions and is another proof for the utility of aryl and hetaryl thioketones in organic synthesis [18]. Another important feature of the presented system with a potential, practical application to materials and coordination chemistry is the release of strictly controlled amounts of
The chemistry and biology of mycolactones
Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159
- Wittig, HWE or Julia olefination with the respective C15–C20 fragments. The most extensive contributions to the synthesis of mycolactones have come from Kishi and co-workers, who pioneered the synthesis of the extended mycolactone core structure. The group’s approaches to this problem have evolved over
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
- suitable olefination strategy. Subsequently, for connecting the resulting fragment to the thiazole subunit 6 a Heck reaction was envisioned as part of studies advancing this type of Palladium-catalyzed coupling strategies in complex target synthesis [61][62][63][64][65][66]. Finally, a HWE-macrocyclization
- 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
- lithium dimethylcuprate. In comparison with the likewise attempted Stork–Zhao olefination this protocol by Tanino and Miyashita was superior in yield and stereoselectivity [80]. To complete the fragment synthesis the [Ru]-catalyzed Trost–Alder-ene reaction [81] generated the desired primary alcohol which
Studies directed toward the exploitation of vicinal diols in the synthesis of (+)-nebivolol intermediates
Beilstein J. Org. Chem. 2017, 13, 571–578, doi:10.3762/bjoc.13.56
- ) was treated with the Wittig reagent Ph3P=CHCO2Et and the resulting unsaturated ester was then hydrogenated with Pd–C and H2 at room temperature to obtain compound 11 in 91% yield over two steps (Scheme 2). DIBAL-H (1.1 equiv, –78 °C) reduction of the ester group of 11 followed by Wittig olefination of
- of the allyl group in 16 with 9-BBN and the oxidation of the resulting organoborane with NaOH and H2O2 furnished alcohol 17 in 96% yield. A one-pot PCC oxidation–Wittig olefination (with Ph3P=CHCO2Et) of 17 provided (E)-α,β-unsaturated ester 18 in 85% yield over 2 steps. Compound 18 was then
(Z)-Selective Takai olefination of salicylaldehydes
Beilstein J. Org. Chem. 2017, 13, 323–328, doi:10.3762/bjoc.13.35
- Stephen M. Geddis Caroline E. Hagerman Warren R. J. D. Galloway Hannah F. Sore Jonathan M. Goodman David R. Spring Department of Chemistry, University of Cambridge, Lensfield Rd, Cambridge, CB2 1EW, UK 10.3762/bjoc.13.35 Abstract The Takai olefination (or Takai reaction) is a method for the
- conversion of aldehydes to vinyl iodides, and has seen widespread implementation in organic synthesis. The reaction is usually noted for its high (E)-selectivity; however, herein we report the highly (Z)-selective Takai olefination of salicylaldehyde derivatives. Systematic screening of related substrates
- led to the identification of key factors responsible for this surprising inversion of selectivity, and enabled the development of a modified mechanistic model to rationalise these observations. Keywords: alkenyl iodides; salicylaldehydes; stereoselectivity; Takai olefination; transition state
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
- -decalins and trans-hydrindanes (Scheme 1) [22][23][24][25]. It relies on the use of sugar-derived allyltin (such as 5) followed by ZnCl2-induced fragmentation into dienoaldehyde 6, subsequent Horner–Wadsworth–Emmons olefination, and intramolecular Diels–Alder reaction. In this paper, we explore the
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
- to orthogonally protected amino acids 46 and 47 (Scheme 7) [58]. Installation of the C-2 stereocentre again began with Garner’s aldehyde 48 and Wittig olefination, followed by Sharpless dihydroxylation to stereoselectively afford diol 49 [59][60]. The C-2 epimer was accessed via Still–Gennari
- olefination of aldehyde 48 to afford the Z-olefin, which underwent dihydroxylation using potassium osmate to afford diol 50 [61][62]. With both diastereomers in hand, conversion to protected amino acids 46 and 47 was effected in four steps. With amino acids 46 and 47 in hand, conversion to the corresponding
- with isothiourea 33 followed by mesyl chloride afforded cyclic guanidine 72 in 70% yield. Silyl deprotection, Swern oxidation and Still–Gennari olefination afforded Z-alkene 73. Diastereoselective dihydroxylation of 73 followed by treatment with 1,1'-thiocarbonyldiimidazole (TCDI) and sodium azide
A new and expeditious synthesis of all enantiomerically pure stereoisomers of rosaprostol, an antiulcer drug
Beilstein J. Org. Chem. 2016, 12, 2234–2239, doi:10.3762/bjoc.12.215
- successfully prepared the enantiomerically pure starting materials (+)-3 and (−)-3, we could proceed with the synthesis of the four stereoisomers of rosaprostol (1). The synthetic pathway to stereoisomers 1a and 1c is outlined in Scheme 4. At first, the Horner olefination reaction of (+)-3 and (−)-3 with
- methyl 5-formylpentanecarboxylate was carried out. The use of a mixture of Al2O3 and KOH as a base in this reaction afforded the corresponding olefination products (−)-(R)-5 and (+)-(S)-5 in high yields. Both of them were formed as mixtures of E and Z-isomers. Although these mixtures were directly used
The direct oxidative diene cyclization and related reactions in natural product synthesis
Beilstein J. Org. Chem. 2016, 12, 2104–2123, doi:10.3762/bjoc.12.200
- ratio of 1.5:1, favoring 99bb (Scheme 21). Glaciapyrrol A (100) was finally obtained from 99ab by deprotection of the benzoyl group and an olefination to connect the pyrrole subunit of the natural product. Leucosceptroids A–D Leucosceptroids A (105a) and B (105b) have been isolated in 2010 by Luo et al
Total synthesis of leopolic acid A, a natural 2,3-pyrrolidinedione with antimicrobial activity
Beilstein J. Org. Chem. 2016, 12, 1624–1628, doi:10.3762/bjoc.12.159
- carried out. Crucial steps for the strategy include a Dieckmann cyclization to obtain the 2,3-pyrrolidinedione ring and a Wittig olefination to install the polymethylene chain. An oxazolidinone-containing leopolic acid A analogue was also synthesized. The antibacterial activity showed by both compounds
- reduction is in agreement with previous results and is consistent with the Cram model for a chelation controlled reduction [16][17][18]. Both OH groups of compound 9 were oxidized by PCC to obtain aldehyde 10. The long carbon chain was incorporated into 10 by Wittig olefination with n
- before, we decided to incorporate the structural features found in leopolic acid into this novel heterocyclic system. Accordingly, Wittig olefination of 14, followed by coupling with L-phenylalanine benzyl ester, and subsequent catalytic hydrogenation in EtOAc of 16 afforded the analogue of leopolic acid
Selective bromochlorination of a homoallylic alcohol for the total synthesis of (−)-anverene
Beilstein J. Org. Chem. 2016, 12, 1361–1365, doi:10.3762/bjoc.12.129
- success in the copper-catalyzed cross coupling of an analogous dichlorotriflate [9], in our hands 2 failed to engage in productive carbon–carbon bond formation. An alternative retrosynthesis traced 1 back to bromochloroaldehyde 3, which should readily engage in standard olefination reactions. As 3 could
- avoided exposure to strong bases or reducing agents, a limitation that significantly guided the choice of reagents and conditions for the subsequent steps. Dess–Martin periodinane oxidation of alcohol 6 followed by Horner–Wadsworth–Emmons olefination with triethyl 2-phosphonopropionate (9) furnished the
- two enantiomers (or pseudoenantiomers) of a substrate allylic alcohol. Tetrahalide 11 was then oxidized to the corresponding aldehyde. Installation of the vinyl bromide was found to be difficult using traditional methods. Takai olefination [14] with CHBr3 and CrBr2 resulted in significant de
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
- explore the selective Wittig mono-olefination of dialdehyde 5 readily accessible from the known 2,3;22,23-epoxysqualene (7) [28]. As depicted in Scheme 1, the synthetic sequence began with the treatment of squalene with two equivalents of NBS in a water/THF mixture. After separation of the bis-bromohydrin
Towards the total synthesis of keramaphidin B
Beilstein J. Org. Chem. 2016, 12, 1096–1100, doi:10.3762/bjoc.12.104
- turn be synthesised by an aminolysis/oxidation/olefination sequence of the terminal alcohol 6, following traceless nitro group removal. 5-Nitropiperidin-2-one 6 in turn could be accessed by a nitro-Mannich lactamisation cascade reaction between Michael adduct 7, formaldehyde and a suitable primary
Cationic Pd(II)-catalyzed C–H activation/cross-coupling reactions at room temperature: synthetic and mechanistic studies
Beilstein J. Org. Chem. 2016, 12, 1040–1064, doi:10.3762/bjoc.12.99
- intermediate, characterized by X-ray analysis. Roles of various additives in the stepwise process have also been studied. Keywords: arylation; cationic palladium; C–H functionalization; green chemistry; olefination; Introduction Transition metal-catalyzed, direct functionalization of aryl C–H bonds has made
- temperature, we next sought to apply our cationic palladium(II) conditions to the venerable Fujiwara–Moritani reaction. As reported back in 1967, this direct aryl olefination reaction is among the first palladium-catalyzed C–H activation reactions to be described [190][191][192]. Subsequent studies have
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
- 10.3762/bjoc.12.94 Abstract An improved protocol for the synthesis of enantiomerically pure allylic amines is reported. N-Protected α-amino esters derived from natural amino acids were submitted to a one-pot tandem reduction–olefination process. The sequential reduction with DIBAL-H at −78 °C and
- and threonine derivatives. Keywords: amino acids; olefination; protecting group free; synthetic methods; Wittig reactions; Introduction Allylic amines have received significant attention because they represent a common scaffold in diverse biologically relevant compounds and natural products [1]. In
- -protected α-amino esters requires three chemical steps, i.e. reduction, oxidation and olefination (Figure 1) [9][10]. When the benzyl group is used as protecting group for the nitrogen functionality, the method represents a variation of the well-known Reetz protocol [11]. In the particular case of serine
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