Synthesis of mono-functionalized S-diazocines via intramolecular Baeyer–Mills reactions

• Miriam Schehr,
• Daniel Hugenbusch,
• Tobias Moje,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2018, 14, 2799–2804, doi:10.3762/bjoc.14.257

• ]. The back isomerization is initiated quantitatively with light within the range of 500–660 nm. Hence, the trans-to-cis isomerization can be performed with red light which is important for medical applications, because blood-supported tissue is transparent in the far red region [27]. For the iodo

• trans isomer are between 1–7 days. These properties are ideal for applications in photopharmacology where the more bulky cis state is the inactive form and the trans isomer is the active configuration. Cis–trans isomerization of mono-functionalized S-diazocines 1–5. UV spectra of the S-diazocine 4 in

Ring-opening metathesis of some strained bicyclic systems; stereocontrolled access to diolefinated saturated heterocycles with multiple stereogenic centers

• Zsanett Benke,
• Melinda Nonn,
• Márton Kardos,
• Santos Fustero and
• Loránd Kiss

Beilstein J. Org. Chem. 2018, 14, 2698–2707, doi:10.3762/bjoc.14.247

• opening of the heteroring, (Scheme 7). The process involves isomerization through olefin bond migration proceeding Z-selectively. Conclusion The ring-opening metathesis (ROM) of some ring-constrained, unsaturated bicyclic frameworks has been studied in the presence of commercially available ruthenium

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• catalysts for chemists because they efficiently mediate difficult organic reactions under mild conditions [46][47][48][49][50][51]. In some catalysis mediated by B12 enzymes, the high reactivity of the adenosyl radical is exploited for isomerization. The microenvironments provided by the apoenzymes activate

• , and Irdfppy system was used for radical-mediated isomerization reactions. Visible-light irradiation of diethyl 2-bromomethyl-2-phenylmalonate produced the phenyl-migrated product (Scheme 10) [104]. The product distribution highly depended on the solvents. The yield of phenyl-migrated products relative

• obtained through isomerization with 1,2-migration of the ester groups. The B12-TiO2 hybrid catalyst can be regarded as a good alternative for conventional radical-involved organic syntheses using tin compounds. Recently, we discovered that the B12 derivative 1 can mediate trifluoromethylation and

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

• substrate 117, which was subjected to RCM with the aid of G-II catalyst 2 to produce a mixture of products 119 and 121 in combined 47% yield. It should be noted that the resulting product 121 was obtained through isomerization of the terminal double bond followed by RCM. Later, oxidation of diols 119 and

Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source

• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221

• )propane), and bpy as ligands afforded the olefin isomerization product as the major product. Further screening of the reaction conditions revealed that the amount of AlMe3 was critical: the product yield increased with decreasing AlMe3 to 1.5 equiv. The concentration of 11a also affected the efficiency of

• the reaction, and the isomerization of olefins could be suppressed at lower concentrations of 11a, affording the desired 12a-Me in 58% yield. With the addition of 1 equiv of CsF, the carboxylation was further accelerated to give 12a-Me in 71% yield. Using optimized reaction conditions, the substrate

• discovered the one-pot synthesis of coumarin derivatives via hydrocarboxylation/alkene isomerization/cyclization reactions (Scheme 22) [49]. A key of the sequential reactions is a use of aromatic alkynes bearing a momo-protected hydroxy group at the ortho position on the aromatic ring (23). The corresponding

Non-metal-templated approaches to bis(borane) derivatives of macrocyclic dibridgehead diphosphines via alkene metathesis

• Tobias Fiedler,
• Michał Barbasiewicz,
• Michael Stollenz and
• John A. Gladysz

Beilstein J. Org. Chem. 2018, 14, 2354–2365, doi:10.3762/bjoc.14.211

• ; crystal structures; homeomorphic isomerization; hydrogenation; in/out isomers; metathesis; phosphine boranes; Introduction We have found that a variety of metal complexes with trans-phosphine ligands of the formula P((CH2)mCH=CH2)3 (1; m = 4–14) undergo threefold interligand ring closing alkene

• 2 and 3: in,in, out,out, and in,out (identical to out,in). The first two, as well as the degenerate in,out pair, can rapidly interconvert by a process termed homeomorphic isomerization [26][27], which is akin to turning the molecules inside out. Readers are referred to earlier publications in this

• triarylphosphorus bridgeheads and p-phenylene containing tethers that are long enough to allow rapid homeomorphic isomerization. The precursor 18·2(=O) was prepared by a threefold Williamson ether synthesis in surprisingly high yields (61% in,in/out,out and in,out combined) [50][51], likely aided by the geminal

The enzymes of microbial nicotine metabolism

• Paul F. Fitzpatrick

Beilstein J. Org. Chem. 2018, 14, 2295–2307, doi:10.3762/bjoc.14.204

• maleamate amidase that catalyzes the hydrolysis of maleamate to maleic acid plus ammonium; it also belongs to the α/ß hydrolase superfamily. Finally, Iso catalyzes the reversible isomerization of maleate to fumarate. Orthologues of all four of these enzymes have been identified as being involved in the

Determining the predominant tautomeric structure of iodine-based group-transfer reagents by ¹⁷O NMR spectroscopy

• Nico Santschi,
• Cody Ross Pitts,
• Benson J. Jelier and
• René Verel

Beilstein J. Org. Chem. 2018, 14, 2289–2294, doi:10.3762/bjoc.14.203

• over 50 kcal/mol, a high kinetic barrier suppresses the [a → b] isomerization (Figure 1) [5][6]. With SCF3 reagent 5a/5b, structure determination was notably challenging and solely provides a solid-state structural perspective. Thus, we wondered whether a correct structural assignment of reagent 5a/b

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• reaction proceeds through concerted hydrogen transfer by an oxidative pathway, reductive elimination, and subsequent isomerization. 1.2 Co(III)-catalyzed hydroarylation of alkynes In 2013, Kanai/Matsunaga and co-workers developed an air-stable Co(III)Cp* catalyst as an economical alternative to Cp*Rh(III

• . Protonation and isomerization generate cobalt complex G4, which is converted into alkenated product 54 by ligand exchange. 4. Hydroarylation of enynes Catalytic cyclization of 1,n-enynes has become as an attractive tool for the preparation of cyclic adducts with a variety of functionalities in a one-pot

Novel photochemical reactions of carbocyclic diazodiketones without elimination of nitrogen – a suitable way to N-hydrazonation of C–H-bonds

• Liudmila L. Rodina,
• Xenia V. Azarova,
• Jury J. Medvedev,
• Dmitrij V. Semenok and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2018, 14, 2250–2258, doi:10.3762/bjoc.14.200

• without elimination of dinitrogen are essentially limited to their isomerization into α-ketodiazirines [19][20][21][22][23][24][25][26] which is usually observed upon irradiation of diazo compounds with longer wavelength UV light. Recently a new light-induced reaction of diazo compounds with retention of

Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules

• Hendrik V. Schröder and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2018, 14, 2163–2185, doi:10.3762/bjoc.14.190

• organic systems. However, a synthetic problem which was still intricate is caused by the four substitution sites of the TTF unit, which result in a mixture of cis and trans isomers, if two different substituents are attached to either one of the two 1,3-dithiolylidene rings. Isomerization can be promoted

Cobalt-catalyzed nucleophilic addition of the allylic C(sp³)–H bond of simple alkenes to ketones

• Tsuyoshi Mita,
• Masashi Uchiyama,
• Kenichi Michigami and
• Yoshihiro Sato

Beilstein J. Org. Chem. 2018, 14, 2012–2017, doi:10.3762/bjoc.14.176

• to 1.5 equiv further improved the yield of 3aa to 54% yield (Table 1, entry 4). The moderate yield was attributed to the generation of the olefin isomerization product derived from 1a (vide infra). We then changed the equivalents of reagents 1a and 2a. Although the yield of 3aa was decreased when the

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

• Yuichi Yoshimura,
• Hideaki Wakamatsu,
• Yoshihiro Natori,
• Yukako Saito and
• Noriaki Minakawa

Beilstein J. Org. Chem. 2018, 14, 1595–1618, doi:10.3762/bjoc.14.137

• -isomer (8%, N7/N9 mixture). On the other hand, consumption of 67 required longer times and subsequent isomerization to 78 was insufficient at 50 °C, giving 78 in 31% yield with the predominant formation of 77 (40%). The separated N7 isomer 77 was successfully isomerized to the desired N9 isomer 78 in 53

• , the PMB-protected epoxide 121 was converted to diene 122. The dihydropyran ring of 123 was constructed by RCM of 122 catalyzed by a Grubbs 1st generation catalyst. The isomerization of the double bond in 123 by treatment with a Wilkinson catalyst under basic conditions afforded glycal 124 (Scheme 16

Three-component coupling of aryl iodides, allenes, and aldehydes catalyzed by a Co/Cr-hybrid catalyst

• Kimihiro Komeyama,
• Shunsuke Sakiyama,
• Kento Iwashita,
• Itaru Osaka and
• Ken Takaki

Beilstein J. Org. Chem. 2018, 14, 1413–1420, doi:10.3762/bjoc.14.118

• arylcobalt species, which then performed allene carbocobaltation to form stereo-defined substituted (Z)-allylcobalt intermediates. The chromium catalyst transformed the generated allylcobalt intermediates into highly nucleophilic allylchromium species, without the isomerization of the olefinic moiety, via

London dispersion as important factor for the stabilization of (Z)-azobenzenes in the presence of hydrogen bonding

• Andreas H. Heindl,
• Raffael C. Wende and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2018, 14, 1238–1243, doi:10.3762/bjoc.14.106

• Andreas H. Heindl Raffael C. Wende Hermann A. Wegner Institut für Organische Chemie, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 17, 35392 Gießen, Germany 10.3762/bjoc.14.106 Abstract The understanding and control of the light-induced isomerization of azobenzenes as one of the most

• isomerization rates of several N-substituted 4,4′-bis(4-aminobenzyl)azobenzenes were measured. An intramolecular stabilization was observed and explained by the interplay of intramolecular amide and carbamate hydrogen bonds as well as London dispersion interactions. Whereas in toluene, 1,4-dioxane and tert

• dispersion forces to be a significant factor, even in the presence of hydrogen bonds. Keywords: azobenzene; hydrogen bonding; London dispersion; molecular switches; Introduction The photo-controlled E→Z isomerization of azobenzene has been known for decades [1] and has originated a wide field of

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

• of catalytic mercury iodide; it is a critical step for the formation of the compound 72. Hydrolysis of intermediate 68 led to ketone 69 in high yield containing an acetic acid residue β to the carbonyl group. A sequence of the one-carbon homologation of ketone 69 is followed by isomerization into the

• preparation of possible intermediate bromo-tetrahydrocyclobuta[a]inden-7-one 167 [136]. As the reaction of 167 does not work under basic conditions, it is supposed that the reaction takes place via an acid-catalyzed double bond isomerization followed by an elimination reaction. Moreover, Ghosh’s group

Phosphodiester models for cleavage of nucleic acids

• Satu Mikkola,
• Tuomas Lönnberg and
• Harri Lönnberg

Beilstein J. Org. Chem. 2018, 14, 803–837, doi:10.3762/bjoc.14.68

• structural change known as Berry pseudorotation [20]: one of the equatorial ligands remains equatorial, while the rest turn apical and the apical ligands equatorial. Several alternative models for isomerization of trigonal-bipyramidal pentacoordinate compounds have been presented [21], but Berry

• reactions of RNA phosphodiester linkages at physiological pH (pH 6–8) are pH-independent isomerization to 2´,5´-bonds (red line in Figure 6) and hydroxide-ion-catalyzed transesterification to a 2´,3´-cyclic phosphate by departure of the 5´-linked nucleoside, followed by subsequent hydrolysis to a mixture of

• 2´- and 3´-phosphates (blue line in Figure 6) [44][45]. These reactions are approximately as fast at pH 7, the isomerization being faster under more acidic and cleavage under more basic conditions. The occurrence of isomerization inevitably shows that the monoanionic phosphorane, most likely

Cobalt-catalyzed directed C–H alkenylation of pivalophenone N–H imine with alkenyl phosphates

• Wengang Xu and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2018, 14, 709–715, doi:10.3762/bjoc.14.60

• obtained in an E-rich form from an E/Z mixture (1:1) of the starting alkenyl phosphate, demonstrating the E/Z isomerization during the C–C-bond formation. The E/Z isomerization was also observed for the conversion of cyclododecenyl phosphate (E/Z = 9:1) to the product 3af (E/Z = 3:1). Expectedly, 4

Stepwise radical cation Diels–Alder reaction via multiple pathways

• Ryo Shimizu,
• Yohei Okada and
• Kazuhiro Chiba

Beilstein J. Org. Chem. 2018, 14, 704–708, doi:10.3762/bjoc.14.59

• material is lost. Indeed, the anodic oxidation of either the Z- (1Z) or the E-form (1E) in the absence of 2,3-dimethyl-1,3-butadiene (2) led to isomerization. In other words, inversion of the configuration of the radical cation 1·+ proceeds readily, leading to a loss in stereoselectivity. The radical

Recent developments in the asymmetric Reformatsky-type reaction

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 325–344, doi:10.3762/bjoc.14.21

• benzoxathiazine 2,2-dioxides, as electrophiles in the catalytic enantioselective aza-Reformatky reaction [49]. Indeed, these compounds constitute good partners for asymmetric catalysis since they exhibit a rigid structure reducing the conformational mobility and avoiding the E/Z isomerization, thus facilitating

Aminosugar-based immunomodulator lipid A: synthetic approaches

• Alla Zamyatina

Beilstein J. Org. Chem. 2018, 14, 25–53, doi:10.3762/bjoc.14.3

The synthesis of the 2,3-difluorobutan-1,4-diol diastereomers

• Robert Szpera,
• Nadia Kovalenko,
• Kalaiselvi Natarajan,
• Nina Paillard and
• Bruno Linclau

Beilstein J. Org. Chem. 2017, 13, 2883–2887, doi:10.3762/bjoc.13.280

• substituents is of interest. Here we describe optimisation efforts in the synthesis of anti-2,3-difluorobutane-1,4-diol, as well as the synthesis of the corresponding syn-diastereomer. Both targets were synthesised using an epoxide opening strategy. Keywords: acetal isomerization; deoxyfluorination; epoxide

The photodecarboxylative addition of carboxylates to phthalimides as a key-step in the synthesis of biologically active 3-arylmethylene-2,3-dihydro-1H-isoindolin-1-ones

• Ommid Anamimoghadam,
• Saira Mumtaz,
• Anke Nietsch,
• Gaetano Saya,
• Cherie A. Motti,
• Jun Wang,
• Peter C. Junk,
• Ashfaq Mahmood Qureshi and
• Michael Oelgemöller

Beilstein J. Org. Chem. 2017, 13, 2833–2841, doi:10.3762/bjoc.13.275

• -to-Z isomerization was caused during acidic work-up or purification. When products 8a and 8j were isolated by extraction under neutral conditions, the high E-selectivity of the dehydration step was retained. After column chromatographic purification on silica gel, partial isomerization to the Z

• acetone/water [34][59]. The high stereoselectivity during the formation of compounds 7a–q is supported by the higher stability of the E-isomer, as shown for other simple N-substituted benzylideneisoindolin-1-ones [12][21]. Remarkably, acidic reaction conditions induced thermal isomerization of compounds

• 8a–y, possibly via an acylaminium cation intermediate (Scheme 9) [60]. The change in stability may be caused by a stabilizing ionic–π interaction for the Z-isomer during isomerization [61]. A similar thermal isomerization towards the more stable isomer induced by catalytic amounts of pyridinium p

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

• Wehman (Scheme 4) [10]. Vinylphosphonium salts can also be prepared by alkylation of phosphines (usually triphenylphosphine) with allyl halide derivatives and isomerization of allylphosphonium salts 4 thus obtained under the influence of bases such as triethylamine or sodium carbonate (Scheme 5) [11][12

• subsequent isomerization of intermediate allylphosphonium salts. Alkylation of triphenylphosphine with vinyl triflates in the presence of (Ph3P)4Pd. Mechanism of alkylation of triphenylphosphine with vinyl triflates in the presence of (Ph3P)4Pd as catalyst. β-Elimination of phenol from β

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

• isomerization or epimerization, cyclic pseudopeptides using Fmoc SPPS [48][50]. Biological studies were conducted on monofluoroalkene-containing analogues of FC131, which is a known antagonist of the chemokine receptor CXCR4. The latter has implications in cancer metastasis and HIV 1 infection. Anti-HIV 1