Synthesis of benzo[d]imidazo[2,1-b]benzoselenoazoles: Cs₂CO₃-mediated cyclization of 1-(2-bromoaryl)benzimidazoles with selenium

• Mio Matsumura,
• Yuki Kitamura,
• Arisa Yamauchi,
• Yoshitaka Kanazawa,
• Yuki Murata,
• Tadashi Hyodo,
• Kentaro Yamaguchi and
• Shuji Yasuike

Beilstein J. Org. Chem. 2019, 15, 2029–2035, doi:10.3762/bjoc.15.199

• -fluorobenzene, and Se powder under the optimized conditions, i.e., in the presence of Cs2CO3 (2 equiv) in DMF under an argon atmosphere at 150 °C. This reaction gave product 2a in only 35% yield, suggesting that the stepwise reaction via 1-(2-bromoaryl)benzimidazole 1 is superior. Next, the photophysical

A review of the total syntheses of triptolide

• Xiang Zhang,
• Zaozao Xiao and
• Hongtao Xu

Beilstein J. Org. Chem. 2019, 15, 1984–1995, doi:10.3762/bjoc.15.194

• trimethylsilyl trifluoromethanesulfonate (TMSOTf) in a diastereoselective and stepwise manner. This novel methodology provides a shorter access to the intermediate 97, which is a key intermediate for the synthesis of triptolide. Recently, photoredox catalysis has emerged as a powerful and high-yielding method

Tautomerism as primary signaling mechanism in metal sensing: the case of amide group

• Vera Deneva,
• Georgi Dobrikov,
• Aurelien Crochet,
• Daniela Nedeltcheva,
• Katharina M. Fromm and
• Liudmil Antonov

Beilstein J. Org. Chem. 2019, 15, 1898–1906, doi:10.3762/bjoc.15.185

• : Theoretically predicted structure of 6K (blue), overlaid with the X-ray structure (red). Right: X-ray structure of 6, #1: x − 1, y, z; #2: x + 1, y, z; H bonds are drawn as blue dashed lines. Left: Absorption spectra of 6 with stepwise addition of Mg(ClO4)2 in acetonitrile (1 – neutral ligand; 7 – complex CMg

Nanopatterns of arylene–alkynylene squares on graphite: self-sorting and intercalation

• Tristan J. Keller,
• Joshua Bahr,
• Kristin Gratzfeld,
• Nina Schönfelder,
• Marcin A. Majewski,
• Marcin Stępień,
• Sigurd Höger and
• Stefan-S. Jester

Beilstein J. Org. Chem. 2019, 15, 1848–1855, doi:10.3762/bjoc.15.180

• other sides of the square is based on the Glaser coupling of acetylene-terminated precursor structures. These side chains give macrocycles with reduced symmetry. They cannot be obtained by the cyclization of small building blocks, but require the stepwise formation of more complex precursors, where the

• information of the chain arrangement in the final molecule structure (and also the 2D nanopattern) is already given in the ring precursor. Therefore, precursor structures were prepared in a stepwise coupling strategy, making use of the trimethylsilyl and the (more polar) (3-cyanopropyl)dimethylsilyl

Application of chiral 2-isoxazoline for the synthesis of syn-1,3-diol analogs

• Juanjuan Feng,
• Tianyu Li,
• Jiaxin Zhang and
• Peng Jiao

Beilstein J. Org. Chem. 2019, 15, 1840–1847, doi:10.3762/bjoc.15.179

• subjected to silica gel chromatography. Compound 4 was used to determine the stereoselectivity of the cycloaddition step as well as for oxidation. Oxidation of the 2-isoxazoline 4 with Jones’ reagent gave a complicated mixture, in which the desired carboxylic acid was not observed (Scheme 2). The stepwise

Synthesis of a [6]rotaxane with singly threaded γ-cyclodextrins as a single stereoisomer

• Jason Yin Hei Man and
• Ho Yu Au-Yeung

Beilstein J. Org. Chem. 2019, 15, 1829–1837, doi:10.3762/bjoc.15.177

• [32][33][34][35][36]. By adopting a stepwise stoppering approach, Anderson and co-workers have synthesized a [3]rotaxane consisting of two different axles, derived from a stilbene and a cyanine, threaded through one γ-CD [33]. Inouye has also reported a [3]rotaxane with two pyrene-derived axles

The cyclopropylcarbinyl route to γ-silyl carbocations

• Xavier Creary

Beilstein J. Org. Chem. 2019, 15, 1769–1780, doi:10.3762/bjoc.15.170

• along with 8% of the alkene 22. It is proposed (Scheme 5) that these products arise from stepwise formation of the cyclopropylcarbinyl cation 23. This cation can rearrange via migration of bond a to give the cyclobutyl cation 24. The cis-nature of the phenyl group and the hydrogen in cation 23

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• efficiently synthesized from the aldehyde (2S,1'R)-6 begining from the addition of phenylmagnesium bromide to give a 4:1 mixture of aziridine alcohols 28 (Scheme 8) [46]. They were subjected a stepwise hydrogenation to form first products of the aziridine ring opening and next N-Boc-protected

Water inside β-cyclodextrin cavity: amount, stability and mechanism of binding

• Stiliyana Pereva,
• Valya Nikolova,
• Silvia Angelova,
• Tony Spassov and
• Todor Dudev

Beilstein J. Org. Chem. 2019, 15, 1592–1600, doi:10.3762/bjoc.15.163

• ). Table 1 lists the enthalpies evaluated at the M062X/6-31G(d,p) level of theory for the stepwise water coordination to the host macrocycle in both the gas phase and aqueous solution. Negative ΔH1 and ΔH78 values imply favorable interactions in both media. Similar trends were observed for enthalpies

• behavior of β-CD in the temperature range from 30 °C to 200 °C, in which only its dehydration takes place, is presented in Figure 5. Both DTA and TG/DTG curves reveal one step dehydration reactions in the range 30–100 °C. This result differs from the observed stepwise weight reduction (due to water release

• location. Inside the β-CD cavern a water cluster is formed by a stepwise consecutive coordination of water guests. The cluster is stabilized by a network of hydrogen bonds mostly between the water molecules themselves and interactions between water ligands and cyclodextrin walls. The general trends

An azobenzene container showing a definite folding – synthesis and structural investigation

• Abdulselam Adam,
• Saber Mehrparvar and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2019, 15, 1534–1544, doi:10.3762/bjoc.15.156

• isomerization’s resulting in a stepwise decrease of the distance of the two macrocycles. Accordingly, the distance between the recognition units at the upper and the lower macrocycle decreases stepwise as well. In the chiral container 5 two identical macrocycles are connected to each other. A further development

• . Initially, we tried to synthesize the chiral foldable container 10 starting from the macrocycles 2a and 3a in a stepwise manner. That means, we intended to react in a first step one macrocycle with two azobenzene units having each one reactive and one protected group. In a second step we wanted to transform

Superelectrophilic carbocations: preparation and reactions of a substrate with six ionizable groups

• Sean H. Kennedy,
• Makafui Gasonoo and
• Douglas A. Klumpp

Beilstein J. Org. Chem. 2019, 15, 1515–1520, doi:10.3762/bjoc.15.153

• conversions, computational and experimental data indicated that the protonated hydroxy groups (oxonium ions) are not persistent intermediates, but rather cleavage of the carbon–oxygen bond is almost instantaneous [12]. It is assumed that ionization to the carbocations occurs in a stepwise process, first

• [1,2-a]indole ring system. The conversion to product 11 also involves a stepwise process – initially forming compound 17 then a second cyclization gives the final product 11. As noted above, no cyclization product 11 was observed when the chemistry was done in the presence of benzene. Only product 10

Synthesis of pyrrolo[1,2-a]quinolines by formal 1,3-dipolar cycloaddition reactions of quinolinium salts

• Anthony Choi,
• Rebecca M. Morley and
• Iain Coldham

Beilstein J. Org. Chem. 2019, 15, 1480–1484, doi:10.3762/bjoc.15.149

• with electron-poor alkenes occurs through a stepwise conjugate addition–cyclization process [23]. We were interested in the related quinolinium ylides that, on (formal) cycloaddition would provide pyrrolo[1,2-a]quinolines as products. These are tricyclic compounds consisting of a pyrrole ring fused

N-doped carbon dots covalently functionalized with pillar[5]arenes for Fe³⁺ sensing

• Jia Gao,
• Ming-Xue Wu,
• Dihua Dai,
• Zhi Cai,
• Yue Wang,
• Wenhui Fang,
• Yan Wang and
• Ying-Wei Yang

Beilstein J. Org. Chem. 2019, 15, 1262–1267, doi:10.3762/bjoc.15.123

• sensing of Fe3+. In addition, the fluorescence intensity of CCDs decreased gradually with the stepwise addition of Fe3+ in the range of 0–500 μM under the excitation at 340 nm (Figure 3c). As illustrated in Figure 3d, the fluorescence intensity versus the concentration of Fe3+ ions (0–190 μM) established

Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• stepwise Pd(II)-catalyzed cascade process or a [4 + 2] cycloaddition reaction, both providing the cis stereochemistry at C-2 and C-3. When the reaction was carried out with the epimer of substrate 33 (having the 5β-hydroxy group), the cis stereochemistry was also achieved at the newly formed C-2 and C-3

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• Kofler apparatus and are uncorrected. NMR spectra were obtained on a Bruker Avance III 500 DRX 600 MHz spectrometer in DMSO-d6. The MALDI–TOF/TOF spectra were measured at Bruker “RapifeX” at MPIP, Germany. The stepwise experimental procedures for the synthesis of compounds 2–4 and characterization data

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• to form supramolecular structures through self-assembly processes by exploiting the weak or non-covalent interactions [10]. Self-assembly is a kinetically reversible process which is more efficient than traditional stepwise synthesis concerning large molecules. Some recent developments in

Homo- and hetero-difunctionalized β-cyclodextrins: Short direct synthesis in gram scale and analysis of regiochemistry

• Gábor Benkovics,
• Mihály Bálint,
• Éva Fenyvesi,
• Erzsébet Varga,
• Szabolcs Béni,
• Konstantina Yannakopoulou and
• Milo Malanga

Beilstein J. Org. Chem. 2019, 15, 710–720, doi:10.3762/bjoc.15.66

• -cyclodextrins The hetero-difunctionalization was performed as a stepwise introduction of an azido and a tosyl moiety into the primary rim of β-CD, in order to obtain a versatile intermediate which allows independent manipulation of two orthogonal functions on the β-CD scaffold. Although the selectivity of the

• reversed-phase HPLC method (reaction 8, Figure 4). With reactions 6, 7 and 8 all the possible regioisomers of 6A-monoazido-6X-monotosyl-β-CD were prepared and due to their different HPLC retention times, they can be used as reference compounds to evaluate the substitution pattern in stepwise hetero

• optimization this chromatographic method can be applied also for preparative purposes. As a final proof for the side-selectivity of stepwise hetero-difunctionalizations, part of the azido-tosylates prepared in reactions 4–8 were transformed to the diazido-β-CDs (reactions 9–13, Scheme 3). As the reversed-phase

Selectivity in multiple multicomponent reactions: types and synthetic applications

• Ouldouz Ghashghaei,
• Francesca Seghetti and
• Rodolfo Lavilla

Beilstein J. Org. Chem. 2019, 15, 521–534, doi:10.3762/bjoc.15.46

• same strategy was exploited by Wessjohann for the synthesis of RGD (Arg-Gly-Asp)cyclopeptoids [51]. In this case, they developed a stepwise protocol in which two Ugi 4CRs, flanking a deprotection, provided linear peptidic adducts. Afterwards, these intermediates were again deprotected and a final Ugi

• . Stepwise access to 6-aminopenicillanic acid derivative through an Asinger, deprotection, Joullié approach. A triple MCR-deprotection approach affording anticancer peptidomimetics. Acknowledgements Financial support from the Ministerio de Economía y Competitividad-Spain (MINECO, CTQ2015-67870-P) and

Silanediol versus chlorosilanol: hydrolyses and hydrogen-bonding catalyses with fenchole-based silanes

• Falco Fox,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2019, 15, 167–186, doi:10.3762/bjoc.15.17

• smaller energy barrier to the TS (Ea = 23.6 kcal mol−1, Table 3, entry 11, Figure 5 and Ea = 21.1 kcal mol−1, Table 3, entry 12, Figure 5). The stepwise hydrolysis of tetrachlorosilane shows that the energy barrier for the first step is higher (Ea = 28.4 kcal mol−1, Table 3, entry 13), than the second

Mechanistic studies of an L-proline-catalyzed pyridazine formation involving a Diels–Alder reaction with inverse electron demand

• Anne Schnell,
• J. Alexander Willms,
• S. Nozinovic and
• Marianne Engeser

Beilstein J. Org. Chem. 2019, 15, 30–43, doi:10.3762/bjoc.15.3

• relevant species of the reaction including the elusive Diels–Alder intermediate II3. The direct observation of this ion is the first experimental proof that the reaction is not concerted, but does proceed in a stepwise manner. The three intermediates could be further characterized by collision-induced

6’-Fluoro[4.3.0]bicyclo nucleic acid: synthesis, biophysical properties and molecular dynamics simulations

• Sibylle Frei,
• Andrei Istrate and
• Christian J. Leumann

Beilstein J. Org. Chem. 2018, 14, 3088–3097, doi:10.3762/bjoc.14.288

• of nucleoside 8 using quantum mechanical methods. The calculations were performed in vacuum with the Gaussian 09 software package [65] utilizing the second order Møller–Plesset perturbation theory (MP2) and the 6-311G* basis set. The energy profile of nucleoside 8 was obtained through a stepwise

Cross metathesis-mediated synthesis of hydroxamic acid derivatives

• Shital Kumar Chattopadhyay,
• Subhankar Ghosh and
• Suman Sil

Beilstein J. Org. Chem. 2018, 14, 3070–3075, doi:10.3762/bjoc.14.285

• . Having established the conditions for stepwise CM and hydrogenation reactions, we extended the study to other substrates (Table 1). For example, the yields of the two steps for dodecene forming 6b and 7b were more or less similar with those for decene when either of the 2nd-generation catalysts was used

Oxidative and reductive cyclization in stiff dithienylethenes

• Michael Kleinwächter,
• Ellen Teichmann,
• Lutz Grubert,
• Martin Herder and
• Stefan Hecht

Beilstein J. Org. Chem. 2018, 14, 2812–2821, doi:10.3762/bjoc.14.259

• + takes place upon oxidation. Both, the isomerization of the double bond of the E-isomer as well as the cyclization reaction are instantaneous on the timescale of the experiment. The closed dication C2+ can be reduced stepwise to its neutral form. In addition, when C2+ is not stabilized by donor

• Information File 1). The two-electron reduction of the closed isomer was found to occur in a stepwise manner as indicated by SEC of C-DTE-PhCN clearly showing an intermediate radical anionic species C−• (Figure S40, Supporting Information File 1). Moreover, the phenomenon of reductive cyclization appears not

• thiophenes possessing donor and acceptor substituents (-Ph/-PhOMe, -Ph(CF3)2/-PhNMe2, and -Ph(CF3)2/-PhOMe) have been investigated [8][40]. However, sufficient separation of the oxidation waves in order to assure a fully stepwise oxidation process is difficult to achieve and could only be realized in the

Unprecedented nucleophile-promoted 1,7-S or Se shift reactions under Pummerer reaction conditions of 4-alkenyl-3-sulfinylmethylpyrroles

• Takashi Go,
• Akane Morimatsu,
• Hiroaki Wasada,
• Genzoh Tanabe,
• Osamu Muraoka,
• Yoshiharu Sawada and
• Mitsuhiro Yoshimatsu

Beilstein J. Org. Chem. 2018, 14, 2722–2729, doi:10.3762/bjoc.14.250

• stepwise procedure succeeded to give 7-phenylselenodiol 10a in 91% yield. Next, we performed the Pummerer reaction of N-β-methallyl sulfoxide 5b in order to clarify the substituent effects on the N-alkenyl groups. Surprisingly, the reaction of 5b afforded the intramolecular cyclised pyrroloazepine 11b. The

• ). First, we examined the Pummerer reactions in the presence of p-methoxybenzenethiol or p-chlorobenzenethiol; however, the reactions yielded the reductive sulfide 4a. We next examined the stepwise process: i) the Pummerer reaction of 5a with TFAA, followed by ii) the usual work-up and successive treatment

Bi-mediated allylation of aldehydes in [bmim][Br]: a mechanistic investigation

• Mrunesh Koli,
• Sucheta Chatterjee,
• Subrata Chattopadhyay and
• Dibakar Goswami

Beilstein J. Org. Chem. 2018, 14, 2198–2203, doi:10.3762/bjoc.14.193

• , when the temperature was increased stepwise from −70 °C to 0 °C, we did not observe any peak due to the formation of 2a. This indicated the inertness of both the allylating species at zero or sub-zero temperature. However, when the mixture was brought to room temperature and stirred for further 30 min