Hypervalent iodine compounds for anti-Markovnikov-type iodo-oxyimidation of vinylarenes

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Mikhail A. Syroeshkin,
• Alexander A. Korlyukov,
• Pavel V. Dorovatovskii,
• Yan V. Zubavichus,
• Gennady I. Nikishin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2018, 14, 2146–2155, doi:10.3762/bjoc.14.188

• -oxyimidation of vinylarenes with I2/PhI(OAc)2 system. Reaction conditions: vinylarene 1a–k (0.5 mmol), N-hydroxyimide 2a,b (0.5 mmol), I2 (0.25 mmol), PhI(OAc)2 (0.3 mmol), DCM (3.0 mL), 20–25 °C, 10 min, under air. rr = regioisomers ratio. aIBX (0.5 mmol) was used instead of PhI(OAc)2, reaction time: 24 h

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• -acetoxysulfenylation of aliphatic alkenes in moderate to good yields but the products are obtained as a mixture of two regioisomers. In the case of cyclohexene, the reaction gave the corresponding 1,2-acetoxysulfide product as a single isomer. Similar results were reported by Marakalala and Kinfe where a catalytic

• [73] (Scheme 39). The reaction was found to be useful in both intra- and intermolecular thioetherification to yield the regioisomers in ratios that were dependent on the steric bulk of the substituents on the alkene (Scheme 39). The reaction was proposed to proceed via initial transfer of the thiolate

[3 + 2]-Cycloaddition reaction of sydnones with alkynes

• Veronika Hladíková,
• Jiří Váňa and
• Jiří Hanusek

Beilstein J. Org. Chem. 2018, 14, 1317–1348, doi:10.3762/bjoc.14.113

• by Taran et al. [4]. In order to avoid duplication our review is therefore focused in more detail on thermal, photochemical as well as metal-catalyzed reactions of sydnones with alkynes and factors that influence the yield and ratio of both possible regioisomers and also the kinetics and mechanism of

• Huisgen et al. found that some non-symmetrical alkynes (oct-1-yne, phenylacetylene and especially methyl propiolate) gave mixture of both pyrazole regioisomers. The following Table 4 summarizes all known examples [1][2][8][20][24][32][33][34][36][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80

• ][81][82][83][84][85][86][87][88][89][90][91][92][93] where the ratio of both possible regioisomers or at least chemical yield of the major regioisomer was given. The first people who qualitatively discussed the regioselectivity on the basis of semi-empirical quantum calculations was Houk et al. [94

The first Pd-catalyzed Buchwald–Hartwig aminations at C-2 or C-4 in the estrone series

• Ildikó Bacsa,
• Dávid Szemerédi,
• János Wölfling,
• Gyula Schneider,
• Lilla Fekete and
• Erzsébet Mernyák

Beilstein J. Org. Chem. 2018, 14, 998–1003, doi:10.3762/bjoc.14.85

• partially or completely saturated in order to get stereochemically different compounds for structure–activity determinations. The saturated derivatives contain a phenyl moiety at C-2 attached through an ethenediyl or ethanediyl linker. Of the synthesized 2- and 4-regioisomers, solely the 2-counterparts

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

• departure of the 5´-linked nucleoside by a factor of 107. The mechanistic proposal has partly been based on Breslow’s studies on hydrolysis of 4-tert-butylcatechol cyclic phosphate by regioisomers of β-cyclodextrins bearing two imidazole groups [60]. This reverse reaction of the cyclization of 4-tert

Volatiles from the xylarialean fungus Hypoxylon invadens

• Jeroen S. Dickschat,
• Tao Wang and
• Marc Stadler

Beilstein J. Org. Chem. 2018, 14, 734–746, doi:10.3762/bjoc.14.62

• α-cadinene (5). The same problem applies to the unambiguous identification of regioisomers of aromatic compounds. We have recently reported on the GC–MS-based identification of the fungal volatiles 1-chloro-3,4-dimethoxybenzene (6) and 1,3-dichloro-4,5-dimethoxybenzene (7) from an endophytic

• Geniculosporium sp. by comparison of the natural products to all possible regioisomers that were obtained by chemical synthesis [9]. Here we report on the identification of the volatiles emitted by the xylarialean fungus Hypoxylon invadens MUCL 54175, a highly interesting pyrenomycete that was recently described

• unambiguous GC–MS-based structural assignment was only possible by comparison to all regioisomers with different substitution patterns at the benzene ring. Results and Discussion The volatiles released by agar plate cultures of Hypoxylon invadens MUCL 54175 were collected through the CLSA headspace method and

Oxidative cycloaddition of hydroxamic acids with dienes or guaiacols mediated by iodine(III) reagents

• Hisato Shimizu,
• Akira Yoshimura,
• Keiichi Noguchi,
• Victor N. Nemykin,
• Viktor V. Zhdankin and
• Akio Saito

Beilstein J. Org. Chem. 2018, 14, 531–536, doi:10.3762/bjoc.14.39

• the amount of diene to 5 equiv, the HDA adducts 3ad–3cd and 3ae–3ce were obtained in moderate to good yields (3ad–3cd: 55–73%, 3ae–3ce: 49–65%; Table 2, entries 8–13). The HDA adducts 3ae–3ce derived from 2e were isolated as mixtures of regioisomers (distal:proximal = 2:1 or 1:1 as determined by 1H

Synthetic and semi-synthetic approaches to unprotected N-glycan oxazolines

• Antony J. Fairbanks

Beilstein J. Org. Chem. 2018, 14, 416–429, doi:10.3762/bjoc.14.30

• partially purified by acetone precipitation and extraction with 60% methanol. The crude N-glycans were found to be a rather complex mixture of compounds, the four major components of which were identified as triantennary glycans with 2 or 3 sialic acids attached as regioisomers (i.e., both α(2–6)- and α(2–3

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

• acetic acid (Scheme 1). In the same report the other regioisomers 6-trifluoromethylpyrazolo[3,4-b]pyridines 20 were obtained under multicomponent solvent-free conditions by the reaction of hydrazine 14, β-ketonitrile 15 and β-diketone 17 as an exclusive product. The structures of both the regioisomers

Progress in copper-catalyzed trifluoromethylation

• Guan-bao Li,
• Chao Zhang,
• Chun Song and
• Yu-dao Ma

Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11

• substituents and generate mixture of regioisomers in some cases. In 2012, the group of Qing [56] designed a copper-catalyzed oxidative trifluoromethylation of heteroarenes and electron-deficient arenes with TMSCF3 through direct C−H activation (Scheme 35). At first, the oxidative trifluoromethylation of 1,3,4

• . These methods have often the drawback of generating mixtures of regioisomers. Future efforts will be focus on developing efficient and less expensive reagents, along with a better understanding of mechanisms, improving the regioselectivity and enantioselectivity in these trifluoromethylation processes

Aminosugar-based immunomodulator lipid A: synthetic approaches

• Alla Zamyatina

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

Recent applications of click chemistry for the functionalization of gold nanoparticles and their conversion to glyco-gold nanoparticles

• Vivek Poonthiyil,
• Thisbe K. Lindhorst,
• Vladimir B. Golovko and
• Antony J. Fairbanks

Beilstein J. Org. Chem. 2018, 14, 11–24, doi:10.3762/bjoc.14.2

• , and gives a mixture of 1,4- and 1,5-triazole regioisomers (Scheme 1) [39]. Interest in and applications of the AAC have surged over the past 15 or so years, since the introduction of Cu(I) catalysis, which led to significant improvements in both the regioselectivity and rates of the reaction [40][41

Acid-catalyzed ring-opening reactions of a cyclopropanated 3-aza-2-oxabicyclo[2.2.1]hept-5-ene with alcohols

• Katrina Tait,
• Alysia Horvath,
• Nicolas Blanchard and
• William Tam

Beilstein J. Org. Chem. 2017, 13, 2888–2894, doi:10.3762/bjoc.13.281

• includes the reduction to form alkane 8 [3], oxidative cleavage of the C=C bond to form 9 [4], ring-opening metathesis to form functionalized alkenes 10 and 11 [4], dihydroxylation to form diol 12 [5], ruthenium-catalyzed [2 + 2] cycloaddition with unsymmetrical alkynes to form regioisomers 13 and 14 [6

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation and chlorination. Part 2: Use of CF₃SO₂Cl

• Hélène Chachignon,
• Hélène Guyon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2800–2818, doi:10.3762/bjoc.13.273

• additional desulfonylation step (Scheme 6) [13]. Both electron-withdrawing and electron-donating groups on para-position of the aryl ring were tolerated, and provided comparable yields. On the other hand, the presence of a substituent in meta-position led to the formation of two regioisomers. As for ortho

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• failed to give the expected product. With a substituent at the meta-position of the aniline ring, a mixture of regioisomers was obtained. Various alkenes with substituents (R3) were investigated and the oxindoles were obtained in moderate to high yields (Scheme 24). Simultaneously, Lei and co-workers

• -substituted phenyl rings produced mixtures of regioisomers. Under these metal-free conditions, it was proposed that the CF3 radical was formed uniquely by reaction of CF3SO2Na with K2S2O8. N-Arylacrylamides could also react with CF3SO2Na under metal-free conditions by replacing tert-butyl hydroperoxide or the

• arenes and heteroarenes: In 1991, Langlois and co-workers reported the first trifluoromethylation of aromatic compounds with sodium trifluoromethanesulfinate under oxidative conditions (Scheme 34) [16]. The scope was quite narrow with electron-rich aromatics and mixtures of regioisomers were often

An efficient synthesis of 1,6-anhydro-N-acetylmuramic acid from N-acetylglucosamine

• Matthew B. Calvert,
• Christoph Mayer and
• Alexander Titz

Beilstein J. Org. Chem. 2017, 13, 2631–2636, doi:10.3762/bjoc.13.261

• regioisomers, out of which the desired anhydroMurNAc derivative 1 could only be isolated in trace quantities from the mixture with isomers 5–11 (Scheme 2). A selective protection of the 4-OH position of 4 has been reported, and as such this tritylation was carried out, delivering 12 in 74% yield [12]. The

Electrophilic trifluoromethylselenolation of terminal alkynes with Se-(trifluoromethyl) 4-methylbenzenesulfonoselenoate

• Clément Ghiazza,
• Anis Tlili and
• Thierry Billard

Beilstein J. Org. Chem. 2017, 13, 2626–2630, doi:10.3762/bjoc.13.260

• . Further, a high regioselectivity is observed but, surprisingly, the anti-Markovnikov regioisomers were obtained. The stereochemistry and regiochemistry were confirmed thanks to the X-ray structure of compound 3a (Figure 1). From a mechanistic point of view, the reaction starts certainly with the

Regioselective decarboxylative addition of malonic acid and its mono(thio)esters to 4-trifluoromethylpyrimidin-2(1H)-ones

• Sergii V. Melnykov,
• Andrii S. Pataman,
• Yurii V. Dmytriv,
• Svitlana V. Shishkina,
• Mykhailo V. Vovk and
• Volodymyr A. Sukach

Beilstein J. Org. Chem. 2017, 13, 2617–2625, doi:10.3762/bjoc.13.259

• Michael-type regioisomer 5a (Table 1, entry 1). The reaction course and the ratio of the regioisomers formed were conveniently monitored by 19F NMR spectroscopy. Acid 4a precipitated in pure form on evaporating toluene and treating the residue with diluted hydrochloric acid. Performing the reaction in a

• it under optimal conditions using toluene or DMSO as solvent and TEA (1 equiv) as catalyst (Table 2). The alkyl substituent at the nitrogen atom of the substrate had no significant effect on the reaction course. In all cases, both regioisomers, 4b–i and 5b–i, were isolated in modest to high yields

¹⁵N-Labelling and structure determination of adamantylated azolo-azines in solution

• Sergey L. Deev,
• Alexander S. Paramonov,
• Tatyana S. Shestakova,
• Igor A. Khalymbadzha,
• Oleg N. Chupakhin,
• Julia O. Subbotina,
• Oleg S. Eltsov,
• Pavel A. Slepukhin,
• Vladimir L. Rusinov,
• Alexander S. Arseniev and
• Zakhar O. Shenkarev

Beilstein J. Org. Chem. 2017, 13, 2535–2548, doi:10.3762/bjoc.13.250

• spectroscopy. For monocyclic derivatives of azoles, the structures of N-alkylated regioisomers can be determined using 2D H-(C)-N multiple bond correlation (HCNMBC) experiments [22][23] using natural isotopic abundance. These experiments rely on the magnetization transfer through 13C-15N J-coupling constants

• ]pyrimidin-7-one and the N-adamantylation of the obtained compounds. The combined analysis of the JCN and JHN couplings permitted the straightforward determination of the adamantylation sites in these azolo-azines, even when a mixture of regioisomers is formed. Results Synthesis. Derivatives of 1,2,4

• adamantyl cation generated from 1-adamantanol in acidic medium [34][35][36][37]. The adamantylation of 13-15N2 led to N2- and N1-regioisomers (15a-15N2 and 15b-15N2, respectively, Scheme 1). Interestingly, according to the possible resonance structures, compound 15a-15N2 should represent a mesoionic

Synthesis and supramolecular properties of regioisomers of mononaphthylallyl derivatives of γ-cyclodextrin

• Markéta Bláhová,
• Sergey K. Filippov,
• Lubomír Kováčik,
• Jiří Horský,
• Simona Hybelbauerová,
• Zdenka Syrová,
• Tomáš Křížek and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2017, 13, 2509–2520, doi:10.3762/bjoc.13.248

• a cross-metathesis between previously described regioisomers of mono-O-allyl derivatives of γ-CD and 2-vinylnaphthalene which gives yields of about 16–25% (2–5% starting from γ-CD). To increase the overall yields, we have developed another method, based on a direct alkylation of γ-CD with 3

• supramolecular polymers [9] multifunctional molecules are assembled in a regular manner. To avoid branching, monosubstituted CDs are required for a linear supramolecular polymer of CDs with guest groups attached. Monosubstituted derivatives of CDs [10] include three regioisomers, namely 2I-O-, 3I-O-, and 6I-O

• -substituted ones. To separate pure regioisomers from their mixture is tricky. Their direct regioselective synthesis is possible, although not easy, because hydroxy groups at different positions of CD have different properties; the hydroxy group at position 6 is the most nucleophilic and basic one, the hydroxy

Fluorination of some highly functionalized cycloalkanes: chemoselectivity and substrate dependence

• Attila Márió Remete,
• Melinda Nonn,
• Santos Fustero,
• Matti Haukka,
• Ferenc Fülöp and
• Loránd Kiss

Beilstein J. Org. Chem. 2017, 13, 2364–2371, doi:10.3762/bjoc.13.233

• -amino ester stereo- and regioisomers, derived from unsaturated cyclic β-amino acids is described. The nucleophilic fluorinations involving hydroxy–fluorine exchange of some highly functionalized alicyclic diol derivatives have been carried out in view of selective fluorination, investigating substrate

• , cispentacin) are relevant antifungal agents [19]. Therefore we have selected some five and six-membered alicyclic dihydroxylated β-amino ester stereo- and regioisomers as model compounds [23][24][25][26], derived from cyclopentene or cyclohexene β-amino acids. These were used in order to evaluate their

Solvent-free copper-catalyzed click chemistry for the synthesis of N-heterocyclic hybrids based on quinoline and 1,2,3-triazole

• Martina Tireli,
• Silvija Maračić,
• Stipe Lukin,
• Marina Juribašić Kulcsár,
• Dijana Žilić,
• Mario Cetina,
• Ivan Halasz,
• Silvana Raić-Malić and
• Krunoslav Užarević

Beilstein J. Org. Chem. 2017, 13, 2352–2363, doi:10.3762/bjoc.13.232

• it increases reaction rates and yields and directs the azide–alkyne cycloaddition exclusively towards 1,4-substituted regioisomers, whereas the non-catalyzed process results in a non-stoichiometric mixture of 1,4- and 1,5-regioisomers. Even though CuAAC reactions are efficiently performed in solution

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

• it was found that the inclusion of the additive TMS-morpholine [36][37] was also required to ensure a high diastereoisomeric excess of 38a. The epoxide 38a was then ring-opened using Et3N·3HF to deliver the difluorodiol 39a as a mixture of regioisomers. This mixture subsequently converged during the

Curcuminoid–BF₂ complexes: Synthesis, fluorescence and optimization of BF₂ group cleavage

• Henning Weiss,
• Jeannine Reichel,
• Helmar Görls,
• Kilian Rolf Anton Schneider,
• Mathias Micheel,
• Michael Pröhl,
• Michael Gottschaldt,
• Benjamin Dietzek and
• Wolfgang Weigand

Beilstein J. Org. Chem. 2017, 13, 2264–2272, doi:10.3762/bjoc.13.223

• increasing electron density of the aromatic system, the emission intensity in the low-energy regime of the spectrum increases. It is also noteworthy, that regarding 2a and 2f, which are regioisomers, the second fluorescence band is more intense for 2f than for 2a. For the complexes containing a brominated

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

• demonstrated that the reaction of highly electron-rich aromatics with nitrosoalkenes NSA14 affords the corresponding α-aryl-substituted oximes 66 in low to moderate yields as mixtures of regioisomers [44] (Scheme 22). Nitrosoalkenes were generated from the corresponding α-halooximes 65 upon treatment with