(Z)-Selective Takai olefination of salicylaldehydes

• Stephen M. Geddis,
• Caroline E. Hagerman,
• Warren R. J. D. Galloway,
• Hannah F. Sore,
• Jonathan M. Goodman and
• David R. Spring

Beilstein J. Org. Chem. 2017, 13, 323–328, doi:10.3762/bjoc.13.35

• formed bond to give the (E)-configured olefin, (E)-2 [5]. The minor (Z)-configured product, (Z)-2, presumably results from the reaction through a less favourable transition state which is nearly identical to 5 but differs in that either the R1 substituent originating from the aldehyde or the X

• observed (Z)-olefin products, (Z)-47. Whilst further experimental data is required in order to bolster this hypothesis, our proposed mechanism should act as a starting point for future detailed mechanistic investigations. Our observation that this alternative pathway is favoured by electron-withdrawing

• discussed above. Conclusion Following our observation of unusually high levels of (Z)-olefin product following Takai olefination of a particular aromatic substrate, systematic screening of related substrates revealed the characteristics a substrate should possess in order to lead to (Z)-selective Takai

The reductive decyanation reaction: an overview and recent developments

• Jean-Marc R. Mattalia

Beilstein J. Org. Chem. 2017, 13, 267–284, doi:10.3762/bjoc.13.30

• second part of their work, they developed adequate conditions to carry out the decyanation reaction without olefin isomerization [18]. They explored several methods for the preparation of 12-butyltricosa-1,22-diene 3 (R = n-C4H9). The reaction was carried out in a slurry of K/Al2O3 in hexane, hexane

• /toluene (1:1) and toluene giving 20%, 63% and 75% of olefin isomerization (from NMR and GC), respectively, for each solvent [34]. This isomerization was attributed to the translocation of the tertiary radical intermediate to a more stable allyl radical leading to the double bond migration. This

• rearrangement was avoided using K/Ph3CH in hexane/ether (3 R = n-C4H9, 41% yield) or K/HMPA/t-BuOH in ether (3 R = n-C4H9, 99% yield). The latter optimized conditions allow the decyanation of alkylcyano α,ω-dienes 2 in quantitative yields with no detection of olefin isomerization (Scheme 3). Radical

Efficient access to β-vinylporphyrin derivatives via palladium cross coupling of β-bromoporphyrins with N-tosylhydrazones

• Vinicius R. Campos,
• Ana T. P. C. Gomes,
• Anna C. Cunha,
• Maria da Graça P. M. S. Neves,
• Vitor F. Ferreira and
• José A. S. Cavaleiro

Beilstein J. Org. Chem. 2017, 13, 195–202, doi:10.3762/bjoc.13.22

• two germinal protons H-2’ of the olefin unit appear as two doublets (J = 1.3 Hz) at 5.81 and 5.56 ppm. The value of the coupling constant and the unique correlation of these two protons with a single carbon (115.5 ppm) observed in HSQC spectra corroborates the proposed structure. The HRMS–ESI

Iodination of carbohydrate-derived 1,2-oxazines to enantiopure 5-iodo-3,6-dihydro-2H-1,2-oxazines and subsequent palladium-catalyzed cross-coupling reactions

• Michal Medvecký,
• Igor Linder,
• Luise Schefzig,
• Hans-Ulrich Reissig and
• Reinhold Zimmer

Beilstein J. Org. Chem. 2016, 12, 2898–2905, doi:10.3762/bjoc.12.289

• tendency of this olefin to polymerize under the conditions applied. Consequently, the change of the olefin component from the methyl to the tert-butyl ester allowed the preparation of the corresponding coupling product syn-14 in significantly better yield. The use of dehydroamino acids such as olefin 16

Multicomponent synthesis of spiropyrrolidine analogues derived from vinylindole/indazole by a 1,3-dipolar cycloaddition reaction

• Manjunatha Narayanarao,
• Lokesh Koodlur,
• Vijayakumar G. Revanasiddappa,
• Subramanya Gopal and
• Susmita Kamila

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

Radical polymerization by a supramolecular catalyst: cyclodextrin with a RAFT reagent

• Kohei Koyanagi,
• Yoshinori Takashima,
• Takashi Nakamura,
• Hiroyasu Yamaguchi and
• Akira Harada

Beilstein J. Org. Chem. 2016, 12, 2495–2502, doi:10.3762/bjoc.12.244

• , including hydrolysis reactions [10][11][12][13][14][15], C–H bond activation [34][35][36], olefin epoxidation [37][38][39], Diels–Alder reactions [40][41][42], 1,3-dipole cycloadditions [43][44], and polymerizations [45][46][47], among others. Selective substrate recognition and activation are essential

A new paradigm for designing ring construction strategies for green organic synthesis: implications for the discovery of multicomponent reactions to build molecules containing a single ring

• John Andraos

Beilstein J. Org. Chem. 2016, 12, 2420–2442, doi:10.3762/bjoc.12.236

• -membered heterocycle containing two adjacent nitrogen atoms. Pyrazole Pyrazole is a well-studied 5-membered heterocycle that has been traditionally synthesized either via the Knorr [151] (1,3-diketone and hydrazine) or von Pechmann [152] (olefin and diazomethane followed by oxidation) strategies. Figure 7

Enduracididine, a rare amino acid component of peptide antibiotics: Natural products and synthesis

• Darcy J. Atkinson,
• Briar J. Naysmith,
• Daniel P. Furkert and
• Margaret A. Brimble

Beilstein J. Org. Chem. 2016, 12, 2325–2342, doi:10.3762/bjoc.12.226

• 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

Organometallic chemistry

• Bernd F. Straub,
• Rolf Gleiter,
• Claudia Meier and
• Lutz H. Gade

Beilstein J. Org. Chem. 2016, 12, 2216–2221, doi:10.3762/bjoc.12.213

• for olefin metathesis catalysis [86][87][90][91][98][99][100][108][132][138][147], the characterization of copper–carbene complexes as intermediates in the cyclopropanation of alkenes [102][106][113][119][120], as well as detailed studies into the mechanism of the hydroformylation of alkenes. An

Synthesis and properties of fluorescent 4′-azulenyl-functionalized 2,2′:6′,2″-terpyridines

• Adrian E. Ion,
• Liliana Cristian,
• Mariana Voicescu,
• Masroor Bangesh,
• Augustin M. Madalan,
• Daniela Bala,
• Constantin Mihailciuc and
• Simona Nica

Beilstein J. Org. Chem. 2016, 12, 1812–1825, doi:10.3762/bjoc.12.171

• confirmed by 1H NMR spectroscopy which reveals two doublets at 8.6 and 8.3 ppm assigned to COCHA=CHB with large coupling constants (JA,B = 15.2–15.6 Hz) indicative of the trans-double bond. In the case of compound 2b, the 1H NMR spectrum showed downfield shifts for the β-olefin proton resonance (9.0 ppm

Three-component synthesis of highly functionalized aziridines containing a peptide side chain and their one-step transformation into β-functionalized α-ketoamides

• Lena Huck,
• Juan F. González,
• Elena de la Cuesta and
• J. Carlos Menéndez

Beilstein J. Org. Chem. 2016, 12, 1772–1777, doi:10.3762/bjoc.12.166

• direct aziridination of an olefin [14] or the reaction of an imine with diazoalkanes. Alternatively, the reaction of imines with various nucleophiles, including aza-Darzens mechanisms, can lead to aziridine products [15]. However, few known methods allow the synthesis of C-trisubstituted aziridines

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

• Franziska Hemmerling and
• Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

• olefin intermediate 26 and subsequent cyclisation to 27 (Scheme 4). The C6 epimers of compounds 25 and 26 were also accepted, but with much lower conversion. In both cases, the configuration at C2 in the cyclic product was exclusively D, highlighting the high stereoselectivity of the domain-catalysed

• experiments. The process starts by oxidoreductase domain MmpE-catalysed epoxidation of the double bond between C10 and C11. Olefin 53 is thus a branching point from which two series of analogous C10–C11 epoxides (53–61) and C10–C11 (not shown) olefins arise (Scheme 9). The fact that the wild-type titers of

• agglomerin A (147) biosynthesis proceeds as a two-step process [143]. An initial acyl transferase Agg4-catalysed acetylation of the primary hydroxy group in 158 is followed by dehydratase Agg5-catalysed acetic acid elimination, leading to olefin 147 (Scheme 22). This mechanism was confirmed by gene knockout

Beta-hydroxyphosphonate ribonucleoside analogues derived from 4-substituted-1,2,3-triazoles as IMP/GMP mimics: synthesis and biological evaluation

• Tai Nguyen Van,
• Audrey Hospital,
• Corinne Lionne,
• Lars P. Jordheim,
• Charles Dumontet,
• Christian Périgaud,
• Laurent Chaloin and
• Suzanne Peyrottes

Beilstein J. Org. Chem. 2016, 12, 1476–1486, doi:10.3762/bjoc.12.144

• and two signals for the olefin carbon atoms at δ = 148.4 ppm and δ = 119.3 ppm for the C4 and the C5, respectively. The regiochemistry of the cycloaddition was unambiguously established using heteronuclear multiple bond correlation (HMBC) experiments to identify long-range (generally 2- or 3-bonds

Ring-whizzing in polyene-PtL₂ complexes revisited

• Oluwakemi A. Oloba-Whenu,
• Thomas A. Albright and
• Chirine Soubra-Ghaoui

Beilstein J. Org. Chem. 2016, 12, 1410–1420, doi:10.3762/bjoc.12.135

• ) complexes rises along with the attendant barriers for haptotropic rearrangements. This has been analyzed and quantified in detail by Massera and Frenking [23] for olefin–ML2 compounds. Computational Details All geometries for the L = PH3 complexes were optimized without symmetry constraints within the DFT

• by means of the low temperature 31P and 13C NMR of COT-Pt(R2PCH2CH2PR2), R = iPr [55]. The transition state that interconnects 28 to 30 is shown in 29. The coordination geometry around Pt is typical of that in η2 olefin complexes. What is novel is that the COT (and C8F8) ring is essentially flat with

Molecular weight control in organochromium olefin polymerization catalysis by hemilabile ligand–metal interactions

• Stefan Mark,
• Hubert Wadepohl and
• Markus Enders

Beilstein J. Org. Chem. 2016, 12, 1372–1379, doi:10.3762/bjoc.12.131

• polymerization. All complexes investigated show very high catalytic activity and the additional side arm minimizes chain-transfer reactions, leading to increase of molecular weights of the resulting polymers. Keywords: chromium single-site catalysts; olefin polymerization; ultra-high molecular weight

• external donors (e.g., solvent molecules, substrates, additives, etc.) may displace a relatively strong intramolecular donor function. Several examples for olefin polymerization catalysts with hemilabile ligands are known and the impact of the hemilabile group on the polymerization behavior can be immense

• role in olefin polymerization [18][19][20][21][22][23][24]. Cyclopentadienyl (Cp)-based chromium complexes exhibit very good ethylene polymerization properties, when the coordination sphere of the chromium center is completed by an additional ligand. Improved stability and hence polymer productivities

Selective bromochlorination of a homoallylic alcohol for the total synthesis of (−)-anverene

• Frederick J. Seidl and
• Noah Z. Burns

Beilstein J. Org. Chem. 2016, 12, 1361–1365, doi:10.3762/bjoc.12.129

• chemoselectively decomposed, via a reductive de-dihalogenation pathway to the corresponding olefin, by heating the crude material to reflux in acetone with sodium iodide. Total synthesis of anverene With scalable access to 6, a total synthesis of (−)-anverene (1) was explored (Scheme 2). Homoprenol (5) was

Artificial Diels–Alderase based on the transmembrane protein FhuA

• Hassan Osseili,
• Daniel F. Sauer,
• Klaus Beckerle,
• Marcus Arlt,
• Tomoki Himiyama,
• Tino Polen,
• Akira Onoda,
• Ulrich Schwaneberg,
• Takashi Hayashi and
• Jun Okuda

Beilstein J. Org. Chem. 2016, 12, 1314–1321, doi:10.3762/bjoc.12.124

• metal complexes As the protein host, the FhuA ΔCVFtev variant of the Ferric hydroxamate uptake protein component A (FhuA) was chosen [31]. This protein was shown to be suitable to harbor Grubbs–Hoveyda type catalysts for olefin metathesis [17][18]. To anchor Cu(I) in the protein FhuA ΔCVFtev that

Stereoselective synthesis of tricyclic compounds by intramolecular palladium-catalyzed addition of aryl iodides to carbonyl groups

• Jakub Saadi,
• Christoph Bentz,
• Kai Redies,
• Dieter Lentz,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2016, 12, 1236–1242, doi:10.3762/bjoc.12.118

• –R2 = (CH2)4] typical Heck reaction conditions employing styrene as olefin component not only led to the desired styrene derivative B but mainly to the cyclized product C. If the reaction was performed without the olefin it provided only the tertiary alcohol C in reasonable yield [5]. Similar C–C bond

Unusual traits of cis and trans-2,3-dibromo-1,1-dimethylindane on the way from 1,1-dimethylindene to 2-bromo-, 3-bromo-, and 2,3-dibromo-1,1-dimethylindene

• Rudolf Knorr,
• David S. Stephenson,
• Ernst Lattke,
• Petra Böhrer and
• Jakob Ruhdorfer

Beilstein J. Org. Chem. 2016, 12, 1178–1184, doi:10.3762/bjoc.12.113

• -bromo-1,1-dimethylindene. Keywords: base-free dehydrobromination; cis/trans stereochemistry; five-membered ring conformation; indenes; NMR couplings; Introduction The basic mechanistic features of competing suprafacial and antarafacial additions of elemental bromine to an olefin are reasonably well

• established [1][2][3]. With indene as a cyclic olefin, the major product trans-1,2-dibromoindane was formed through antarafacial addition; the accompanying cis diastereomer resulted through the suprafacial bromine addition and rarely [4] exceeded 30% of the diastereomeric trans/cis product mixture. For the

• a most unusual, highly cis selective olefin bromination. What else may appear unusual with 1 and its congeners? Trans-1 and cis-1 undergo regiospecific HBr eliminations even in the absence of bases, cis-1 does so more rapidly than trans-1. The products 3 and 4, respectively, can serve as precursors

Synthesis of 2-oxindoles via 'transition-metal-free' intramolecular dehydrogenative coupling (IDC) of sp² C–H and sp³ C–H bonds

• Nivesh Kumar,
• Santanu Ghosh,
• Subhajit Bhunia and
• Alakesh Bisai

Beilstein J. Org. Chem. 2016, 12, 1153–1169, doi:10.3762/bjoc.12.111

• –Trost decarboxylative geranylations/reverse-geranylations [62][63]. However, conditions B (NIS) were found unsuccessful in case of β-N-arylamidoallyl, methallyl, dimethylallyl, and geranyl esters 9. We speculate that the olefin functionality of substrates might be reacting with NIS (conditions B) faster

Chiral cyclopentadienylruthenium sulfoxide catalysts for asymmetric redox bicycloisomerization

• Barry M. Trost,
• Michael C. Ryan and
• Meera Rao

Beilstein J. Org. Chem. 2016, 12, 1136–1152, doi:10.3762/bjoc.12.110

• (MeCN)3PF6-catalyzed variant of the same reaction that proceeds even at room temperature [10]. The ruthenium process differs from the initially-discovered palladium reaction in that it produces cyclic 1,4-dienes exclusively; no olefin isomerization is detected (Scheme 1, path b). Moreover, ruthenium can

• rings 40, alkenes 42, and alkynes 44 are all tolerated and remain intact under the reaction conditions. The reaction can also tolerate branching at the internal position of the pendant olefin, as polycyclic 46 and 48 displayed excellent enantiomeric ratios. It is also important to point out that no ring

• coordination. The pendant olefin prefers to approach the carbene anti to the aforementioned sulfoxide, resulting in the observed enantiomer of 53. In THF, the rate of epimerization is significantly slower than the [2 + 2] cycloaddition, which means that the enantiomeric ratios observed in the products are

Synthesis of a deuterated probe for the confocal Raman microscopy imaging of squalenoyl nanomedicines

• Eric Buchy,
• Branko Vukosavljevic,
• Maike Windbergs,
• Dunja Sobot,
• Camille Dejean,
• Simona Mura,
• Patrick Couvreur and
• Didier Desmaële

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

Towards the total synthesis of keramaphidin B

• Pavol Jakubec,
• Alistair J. M. Farley and
• Darren J. Dixon

Beilstein J. Org. Chem. 2016, 12, 1096–1100, doi:10.3762/bjoc.12.104

• catalyst. We reasoned that a similar catalytic approach could be used to fix the absolute stereochemical configuration in the Michael addition reaction between δ-valerolactone pronucleophile 8 and nitro-olefin 9, although a degree of uncertainty as to the relative stereochemical outcome of the catalyst

Enantioselective carbenoid insertion into C(sp³)–H bonds

• J. V. Santiago and
• A. H. L. Machado

Beilstein J. Org. Chem. 2016, 12, 882–902, doi:10.3762/bjoc.12.87

• independently by Hashimoto [65][66] and Kan [67] based on an enantioselective intramolecular rhodium carbenoid insertion into C(sp3)–H bonds. In 2012, Pavlyuk and coworkers performed the synthesis of azacycloalkenes by rhodium carbenoid insertion into C(sp3)–H bonds, and subsequent ring closing olefin

Muraymycin nucleoside-peptide antibiotics: uridine-derived natural products as lead structures for the development of novel antibacterial agents

• Daniel Wiegmann,
• Stefan Koppermann,
• Marius Wirth,
• Giuliana Niro,
• Kristin Leyerer and
• Christian Ducho

Beilstein J. Org. Chem. 2016, 12, 769–795, doi:10.3762/bjoc.12.77

• muraymycins. The latest and optimised synthesis is shown in Scheme 2 [92]. Oxidation of the isopropylidene-protected uridine 12 to the 5'-aldehyde and a Wittig reaction [93] gave olefin 13. The key step was a subsequent asymmetric Sharpless aminohydroxylation [94] furnishing (5'S,6'S)-nucleosyl amino acid 14