Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

An efficient synthesis of the guaiane sesquiterpene (−)-isoguaiene by domino metathesis

• Yuzhou Wang,
• Ahmed F. Darweesh,
• Patrick Zimdars and
• Peter Metz

Beilstein J. Org. Chem. 2019, 15, 858–862, doi:10.3762/bjoc.15.83

• keto aldehyde 18. Chemoselective dibromoolefination with ylide 19 prepared from dibromomethyltriphenylphosphonium bromide and sodium tert-butoxide [22] led to ketone 20 virtually without erosion of the relative configuration (dr = 22:1). After subjecting 20 to carbonyl olefination with unsaturated

• to 26 only proceeded with a maximum yield of 20%. Asymmetric Michael addition of aldehyde 26 to methyl vinyl ketone (15) followed immediately by treatment of the resultant unstable keto aldehyde 27 with ylide 19 delivered dibromo olefin 28 with high diastereocontrol (dr = 19:1). Olefination of ketone

• ketone 20, the one-pot conversion of ketone 28 by olefination with unsaturated ylide 21 and alkyne formation with butyllithium yielded dienediyne 8 as a 1.3:1 mixture of E and Z olefin isomers. Gratifyingly, treatment of 8 with 25 mol% of the first generation Grubbs catalyst 29 produced the desired

Synthesis of the aglycon of scorzodihydrostilbenes B and D

• Katja Weimann and
• Manfred Braun

Beilstein J. Org. Chem. 2019, 15, 610–616, doi:10.3762/bjoc.15.56

• = R2 = H, instead of β-glycosyl, respectively). Results and Discussion Most syntheses of dihydrostilbenes rely on a carbonyl olefination followed by hydrogenation of the stilbene [7][8][9]. However, this route appeared not attractive, particularly as our attempts to hydrogenate highly substituted

Synthesis of 1,2-divinylcyclopropanes by metal-catalyzed cyclopropanation of 1,3-dienes with cyclopropenes as vinyl carbene precursors

• Jesús González,
• Alba de la Fuente,
• María J. González,
• Laura Díez de Tejada,
• Luis A. López and
• Rubén Vicente

Beilstein J. Org. Chem. 2019, 15, 285–290, doi:10.3762/bjoc.15.25

• cyclopropanes contrasts with the existence of few straightforward routes for their syntheses. Typical methods rely on the use of reagents containing the required cyclopropane ring, which involve multistep sequences for the installation of adequate functionalization. Thus, Wittig-type olefination with

Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• ) [53]. Starting from O-benzyl-D-serine (2S,3R)-2 was obtained in a similar way. Configurationally stable D-serinal derivative (R)-23 (prepared from D-serine [54]) which primarily exists as hemiacetal was subjected to cis-olefination with Stille's reagent at −30 °C to produce (S)-24 in good yield

• a protected serinal (R)-23 [54]. Wittig olefination extended the alkyl chain by two carbon atoms and simultaneously installed the C=C bond which was subjected to the intramolecular epoxidation to give a >20:1 mixture of aminoepoxides with the isomer (2S,3R,4R)-117 dominating. Without isolation this

• O-benzyl-L-serine. Reagents and conditions: a) (CF3CH2O)2P(O)CH2COOMe, KHMDS, 18-crown-6; b) I2, MeCN; c) Bu3SnH, AIBN, benzene, reflux; d) H2, 10% Pd/C, ethanol; e) CrO3, acetone, then CH2N2, ether; f) 3 M HCl, 80 °C. Synthesis of (2S,3R)-2 employing a one-pot cis-olefination–conjugate addition

Ring-closing-metathesis-based synthesis of annellated coumarins from 8-allylcoumarins

• Christiane Schultze and
• Bernd Schmidt

Beilstein J. Org. Chem. 2018, 14, 2991–2998, doi:10.3762/bjoc.14.278

• Christiane Schultze Bernd Schmidt Universität Potsdam, Institut fuer Chemie, Karl-Liebknecht-Straße 24–25, D-14476 Potsdam-Golm, Germany 10.3762/bjoc.14.278 Abstract 8-Allylcoumarins are conveniently accessible through a microwave-promoted tandem Claisen rearrangement/Wittig olefination

• 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

• groups of Harwood [31][32] and Mali [33][34][35][36], and its Wittig olefination/cyclization part has been employed in the synthesis of various coumarins without alkyl substituents at position 8 [37][38][39]. In all previous reports conventional heating was used to induce the tandem sequence. In this

Synergistic approach to polycycles through Suzuki–Miyaura cross coupling and metathesis as key steps

• Sambasivarao Kotha,
• Milind Meshram and
• Chandravathi Chakkapalli

Beilstein J. Org. Chem. 2018, 14, 2468–2481, doi:10.3762/bjoc.14.223

• generated the cross-coupling product 22 (72%). Next, aldehyde 22 was subjected to Wittig olefination to provide the corresponding alkene 23 (69%), which on subsequent treatment with KOt-Bu in THF gave the isomerized product 24 (73%). Later, RCM of isomerized olefin 24 with the help of G-II catalyst offered

• end, aldehydes 58a,b were subjected to a Wittig olefination followed by condensation with acryloyl chloride (60) to generate the corresponding diolefinic substrates such as 61a (70%) and 61b (65%). Later, these diolefins 61a,b were subjected to RCM with the aid of G-II catalyst 2 to furnish the

Stereoselective total synthesis and structural revision of the diacetylenic diol natural products strongylodiols H and I

• Pamarthi Gangadhar,
• Sayini Ramakrishna,
• Ponneri Venkateswarlu and
• Pabbaraja Srihari

Beilstein J. Org. Chem. 2018, 14, 2313–2320, doi:10.3762/bjoc.14.206

• to Wittig olefination reaction with triphenylphosphonium salt of n-nonyl bromide 15 in presence of n-BuLi to produce the corresponding Z-olefin 28 exclusively in 83% yield. Di-desilylation of compound 28 was easily achieved with n-tetrabutylammonium fluoride to furnish the target molecule

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• exact definition of a reaction employed in LSF, Jiang and co-workers have described a procedure that allows the enantioselective aerobic olefination of α-amino sp3 C–H bonds, using cooperative asymmetric and organocatalysed photoredox catalysis (Scheme 29) [73]. This may not allow for direct

Oligonucleotide analogues with cationic backbone linkages

• Melissa Meng and
• Christian Ducho

Beilstein J. Org. Chem. 2018, 14, 1293–1308, doi:10.3762/bjoc.14.111

• route using Wittig–Horner olefination and catalytic asymmetric hydrogenation as key steps (reactions not shown) [86][87][90][91][92]. Using 'dimeric' building blocks (S)-49, (R)-49, (S)-50, and (R)-50 (Scheme 5), automated DNA synthesis under standard conditions enabled the preparation of partially

• peptide synthesis using the monomeric 3'-amino-nucleosyl amino acids (S)-56 and (R)-56, respectively, as building blocks. The synthesis of thymidinyl amino acids 56 was again started from a corresponding 5'-aldehyde 57 using Wittig–Horner olefination and catalytic asymmetric hydrogenation as key steps

Atom-economical group-transfer reactions with hypervalent iodine compounds

• Andreas Boelke,
• Peter Finkbeiner and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2018, 14, 1263–1280, doi:10.3762/bjoc.14.108

• values (66% for 33b) are obtained. In another tandem procedure, a metal-free C(sp3)–H olefination of amidines 34 with DMSO and PIDA derivatives 20b was developed by Namitharan and co-workers [49]. A Pd(II)-catalysed Heck reaction of the formed exocyclic double bond with the emerging iodoarene yields

• amination–arylation sequence. Auto-amination and cross-coupling of PIDA derivatives 20c. Tandem C(sp3)–H olefination/C(sp2)–H arylation. Atom efficient functionalisations with benziodoxolones 36. Atom-efficient synthesis of furans 39 from benziodoxolones 36a and their further derivatisations

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

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

• Akira Yoshimura,
• Michael T. Shea,
• Cody L. Makitalo,
• Melissa E. Jarvi,
• Gregory T. Rohde,
• Akio Saito,
• Mekhman S. Yusubov and
• Viktor V. Zhdankin

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

• Bettina Riedl and
• Walther Schmid

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

• Jingbo Yu,
• Zikun Hong,
• Xinjie Yang,
• Yu Jiang,
• Zhijiang Jiang and
• Weike Su

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

• Ernesto Emmanuel López-López,
• José Alvano Pérez-Bautista,
• Fernando Sartillo-Piscil and
• Bernardo A. Frontana-Uribe

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

• Anna Kuźnik,
• Roman Mazurkiewicz and
• Beata Fryczkowska

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

• Myriam Drouin and
• Jean-François Paquin

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

• Raju Cheerlavancha,
• Ahmed Ahmed,
• Yun Cheuk Leung,
• Aggie Lawer,
• Qing-Quan Liu,
• Marina Cagnes,
• Hee-Chan Jang,
• Xiang-Guo Hu and
• Luke Hunter

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

• Yaroslav D. Boyko,
• Valentin S. Dorokhov,
• Alexey Yu. Sukhorukov and
• Sema L. Ioffe

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

• Shital Kumar Chattopadhyay,
• Suman Sil and
• Jyoti Prasad Mukherjee

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

• Grzegorz Mlostoń,
• Paulina Pipiak,
• Róża Hamera-Fałdyga and
• Heinz Heimgartner

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

• Matthias Gehringer and
• Karl-Heinz Altmann

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

• Stephan Scheeff and
• Dirk Menche

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

• Runjun Devi and
• Sajal Kumar Das

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