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

• efficient operation and characterization of TTF-based MIMs on a suitable laboratory timescale. The observed stability of the two oxidation states can be explained by the stepwise aromatization of the TTF system. In the neutral state, TTF consists of two pro-aromatic 1,3-dithiolylidene rings which are

• alkylation of 1,3-dithiole-2-thiones C and E and the corresponding TTF molecules derived from them often in very good yields. An additional strategy to obtain non-symmetrically substituted TTF derivatives is the stepwise reaction of TTF tetrathiolate with different electrophiles [48]. Another important

• ) [111]. Crystal structures of catenanes 29 and 30 showed that both TTF units are in the cavity of the central ring in the unswitched state. During the stepwise oxidation, both catenanes display characteristic spectroscopic features for stable mixed-valence (TTF2)●+ and radical-cation (TTF●+)2 dimers

A pyridinium/anilinium [2]catenane that operates as an acid–base driven optical switch

• Sarah J. Vella and
• Stephen J. Loeb

Beilstein J. Org. Chem. 2018, 14, 1908–1916, doi:10.3762/bjoc.14.165

• (Figure 2) was synthesized using a one-step, self-assembly procedure from two bis(pyridinium)ethane axles, two terphenyl spacers and two DB24C8 crown ethers, a [2]catenane with different recognition sites requires a stepwise approach involving the incorporation of each recognition site independently

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

• class of nucleosides with antiviral activity [74]. First, they tried to synthesize acyclic nucleosides in a stepwise manner. The substrates 128 and 129 for the fragmentation reaction were synthesized from ribose in a few steps by the conventional method. The oxidative scission of 128 and 129 was carried

• ’-trans isomers as major products (Scheme 17). Based on the conditions for the stepwise fragmentation and glycosylation procedure, Boto et al. explored the one-pot version of the reaction [74]. When the β-fragmentation, the first step of oxidative glycosylation, was carried out in CH2Cl2 and then the

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

• Gwendal Grelier,
• Benjamin Darses and
• Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

• π-bond via the asynchronous concerted addition of a singlet species or a stepwise radical pathway (Scheme 42) [83][84]. While these transformations cannot be performed under conditions catalytic in iodine, recent investigations have revealed the possibility to value the iodoarene side-product in a

Two new 2-alkylquinolones, inhibitory to the fish skin ulcer pathogen Tenacibaculum maritimum, produced by a rhizobacterium of the genus Burkholderia sp.

• Dandan Li,
• Naoya Oku,
• Atsumi Hasada,
• Masafumi Shimizu and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2018, 14, 1446–1451, doi:10.3762/bjoc.14.122

• ) eluted with a stepwise gradient of 25, 40, 55, and 85% (v/v) MeCN in 50 mM NaClO4. The most active third fraction (37.4 mg) was purified by reversed-phase HPLC on a Cosmosil AR-II column (Ø 1 × 25 cm) with a linear gradient elution program [eluents: MeOH (A), 1:1 CH3CN/H2O (B); 0–5 min 100% B, 5–45 min

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

Recyclable hypervalent-iodine-mediated solid-phase peptide synthesis and cyclic peptide synthesis

• Dan Liu,
• Ya-Li Guo,
• Jin Qu and
• Chi Zhang

Beilstein J. Org. Chem. 2018, 14, 1112–1119, doi:10.3762/bjoc.14.97

• -HPLC yielded the precursor 2 (see Supporting Information File 1). Alternatively, the synthesis of the precursor 2 can be achieved through a convergent [3 + 4] segment condensation strategy in solution phase (Scheme 5). Notably, during the synthesis of tetrapeptide segment 10, the stepwise manner was

Synthetic avenues towards a tetrasaccharide related to Streptococcus pneumonia of serotype 6A

• Aritra Chaudhury,
• Mana Mohan Mukherjee and
• Rina Ghosh

Beilstein J. Org. Chem. 2018, 14, 1095–1102, doi:10.3762/bjoc.14.95

• oligosaccharide synthesis. We have synthesized the aforesaid tetrasaccharide (SPn 6A) based on both stepwise and sequential one-pot glycosylation reactions using easily accessible common building blocks; eventually similar overall yields were obtained in both cases. Keywords: carbohydrates; glycosylation

• ]. After this, the Demchenko group improved these early reports with a convergent approach using glycosyl thioimidates as complementary glycosyl donors with respect to thioglycosides [22][23][24][25]. Herein, we wish to report synthetic routes to the SPn 6A tetrasaccharide via stepwise as well as one-pot

• sequential glycosylation strategies. Results and Discussion Keeping in mind our objective to synthesize the SPn 6A tetrasaccharide following stepwise as well as one-pot synthetic strategies based on common building blocks, a retrosynthetic analysis was made which led us to galactose-based donor 2 [26

Hypervalent iodine-guided electrophilic substitution: para-selective substitution across aryl iodonium compounds with benzyl groups

• Cyrus Mowdawalla,
• Faiz Ahmed,
• Tian Li,
• Kiet Pham,
• Loma Dave,
• Grace Kim and
• I. F. Dempsey Hyatt

Beilstein J. Org. Chem. 2018, 14, 1039–1045, doi:10.3762/bjoc.14.91

• ). These key features in the substitution pattern of the substrate scope led to experiments where tests were performed to better understand, if the HIGES reaction is a concerted mechanism, like RICR, or a stepwise process. In the article and further in a footnote of Khatri and Zhu’s publication [11

• ] compelling evidence was shown by deuterium labelling studies supporting a concerted intramolecular mechanism (RICR) occurring rather than a stepwise intermolecular one. To corroborate their findings with our own, we investigated the HIGES reaction through crossover experiments which appear to conclude a

• concerted mechanism is occurring (Scheme 2). Two crossover reactions were performed for both iodobenzene (4) and 2-iodoanisole (5) to prevent substrate bias. One stepwise mechanism that the results in Scheme 2 eliminate is the possibility that the I(III) is decomposing to I(I) and then subsequently reacts

An efficient and facile access to highly functionalized pyrrole derivatives

• Meng Gao,
• Wenting Zhao,
• Hongyi Zhao,
• Ziyun Lin,
• Dongfeng Zhang and
• Haihong Huang

Beilstein J. Org. Chem. 2018, 14, 884–890, doi:10.3762/bjoc.14.75

• delight, the reaction outcome was satisfactory with a total yield of 47% for three-steps which was equivalent to the stepwise reactions (Scheme 2, 12a). In order to evaluate the generality of this process, we explored a variety of aldehydes 7b–j, and the results are shown in Scheme 2. All tested

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

• dissociative nature, respectively. The pentacoordinated species, called pentaoxyphosphorane, may also have a sufficiently long life-time to represent a minimum on the energy profile. The reaction then proceeds in a stepwise manner. It is an associative nucleophilic displacement (AN + DN) with late transition

• leaving groups that are less basic than EtO−, such as 5´-O− of nucleoside, the lifetime expectedly is shorter. If the leaving group is very good, such as an aryl group, a synchronous concerted mechanism (ANDN) may take over the stepwise mechanism (AN + DN). Model compounds and experimental tools Studies

• original mechanistic suggestion is in principle valid, but has to be supplemented with a general base-catalyzed reaction through a dianionic phosphorane transition state (Scheme 5) that takes place in parallel with the stepwise reaction through a phosphorane monoanion (Scheme 4). The group of Kirby has

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

• -8588, Japan 10.3762/bjoc.14.59 Abstract Herein we disclose the radical cation Diels–Alder reaction of aryl vinyl ethers by electrocatalysis, which is triggered by an oxidative SET process. The reaction clearly proceeds in a stepwise fashion, which is a rare mechanism in this class. We also found that

• two distinctive pathways, including “direct” and “indirect”, are possible to construct the Diels–Alder adduct. Keywords: Diels–Alder reaction; radical cation; rearrangement; single electron transfer; stepwise; Introduction Umpolung, also known as polarity inversion, is a powerful approach in

• course of our study, we discovered that radical cation Diels–Alder reactions are also possible by electrocatalysis, however, the scope was limited to styrenes [34]. Described herein is a stepwise radical cation Diels–Alder reaction of enol ethers by electrocatalysis, which proceeds via multiple unique

Liquid-assisted grinding and ion pairing regulates percentage conversion and diastereoselectivity of the Wittig reaction under mechanochemical conditions

• Kendra Leahy Denlinger,
• Lianna Ortiz-Trankina,
• Preston Carr,
• Kingsley Benson,
• Daniel C. Waddell and
• James Mack

Beilstein J. Org. Chem. 2018, 14, 688–696, doi:10.3762/bjoc.14.57

• used in liquid-assisted grinding (LAG) and properly chosen counter-ion pairing increases the percentage conversion of stilbenes in a mechanochemical Wittig reaction. Utilizing stepwise addition/evaporation of ethanol in liquid-assisted grinding also allows for the tuning of the diastereoselectivity in

• identifying the caesium–bromine pair was optimal for the conversion, caesium carbonate was the base of choice for the described stepwise study with ethanol. Tuning liquid-assisted grinding with ethanol Because using ethanol (high dielectric constant) as the LAG solvent afforded the highest conversion to

• (Table 5). Because the formation of the phosphonium salt is the first step of the Wittig reaction, the question arose whether performing the reaction stepwise could influence our ability to select for both percent conversion and diastereoselectivity. Using a stepwise reaction approach with ethanol as the

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

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• oxidation as well as the oxidation and deprotonation of the radical benzothiophene precursors are accomplished by a [CoIII] catalyst in a second catalytic cycle. [CoIII] is stepwise reduced to [CoI]. Protonation leads to a [CoIII] hydride complex generating dihydrogen by protonation. Quantitative H2

Aminosugar-based immunomodulator lipid A: synthetic approaches

• Alla Zamyatina

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

• diglucosamine backbone of lipid A which allows for a stepwise introduction of multiple functional groups into the molecule are discussed. Thorough consideration is also given to the synthesis of 1,1′-glycosyl phosphodiesters comprising partial structures of 4-amino-4-deoxy-β-L-arabinose modified Burkholderia

• substructures substituted by one Kdo residue at position 6’ and/or modified with ethanolamine at the glycosidic phosphate were accomplished just recently [21][87][88]. The synthetic strategy relied on the initial preparation of fully orthogonally protected βGlcN(1→6)GlcN disaccharide which was then stepwise

• permanent benzyl/benzylidene acetal protections for hydroxyl groups and application of 9-fluorenylmethoxycarbamate (Fmoc) and azido protecting groups for masking the NH2 functionalities allowed for the stepwise instalment of functional groups (phosphates and fatty acids) into the diglucosamine 44. For the

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

• SPAAC in their one-pot stepwise preparation of GAuNPs, and then used those particles as supramolecular glycoprobes for the rapid serological recognition of a cancer biomarker. Firstly, ligand exchange was performed on Cit-AuNPs by reaction with a THF solution of a cyclooctyne disulfide and an aqueous

What contributes to an effective mannose recognition domain?

• Christoph P. Sager,
• Deniz Eriş,
• Martin Smieško,
• Rachel Hevey and
• Beat Ernst

Beilstein J. Org. Chem. 2017, 13, 2584–2595, doi:10.3762/bjoc.13.255

• -energy transition state. This can be explained by the stepwise dissociation and subsequent rehydration that are required for ligand displacement (inset, Figure 2B), due to the inherently shielded nature of the buried binding site. In contrast, solvent exposed H-bonds can be more easily substituted by

A concise flow synthesis of indole-3-carboxylic ester and its derivatisation to an auxin mimic

• Marcus Baumann,
• Ian R. Baxendale and
• Fabien Deplante

Beilstein J. Org. Chem. 2017, 13, 2549–2560, doi:10.3762/bjoc.13.251

• ) mediated reduction and is consistent with a stepwise reduction mechanism (Scheme 5) [27][28][29]. It is evident from the sequence that several equivalents of hydrogen are necessary for full reduction and as a result a higher concentration (pressure) of hydrogen would be beneficial (Table 2, entries 4–10

• for the synthesis intermediate 11. Stepwise reduction of intermediate 11 under hydrogenation conditions. * Indicates potential tautomeric structure. Species in parentheses are proposed transient intermediates. Flow sequence for the construction of product 8. Assembled process for flow synthesis of

Exploring mechanochemistry to turn organic bio-relevant molecules into metal-organic frameworks: a short review

• Vânia André,
• Sílvia Quaresma,
• João Luís Ferreira da Silva and
• M. Teresa Duarte

Beilstein J. Org. Chem. 2017, 13, 2416–2427, doi:10.3762/bjoc.13.239

• carried out with success. These studies show the propensity for stepwise mechanisms, especially in case of ZIFs, with a low density or a highly solvated product often formed first which is then transformed into increasingly dense, less solvated materials, resembling Ostwald’s rule of stages [8][102][103

One-pot syntheses of blue-luminescent 4-aryl-1H-benzo[f]isoindole-1,3(2H)-diones by T3P^® activation of 3-arylpropiolic acids

• Melanie Denißen,
• Alexander Kraus,
• Guido J. Reiss and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2017, 13, 2340–2351, doi:10.3762/bjoc.13.231

• ), an electron-rich (1b) and electron-poor (1c) propiolic acid substrate (Scheme 4, Table 4). Although the electroneutral and electron-rich substrates give good to excellent yields in the sequence (Table 4, entries 1–3), even higher (Table 4, entry 1) than for a stepwise synthesis furnishing an overall

Synthesis and application of trifluoroethoxy-substituted phthalocyanines and subphthalocyanines

• Satoru Mori and
• Norio Shibata

Beilstein J. Org. Chem. 2017, 13, 2273–2296, doi:10.3762/bjoc.13.224

• compared with homodimers [141]. This heterodimer was synthesized by a stepwise synthesis method in which a phthalocyanine unit was first synthesized and then a subphthalocyanine unit was formed (Scheme 13). The synthesis of Pc-subPc was carried out as follows. First, A3B type diiodophthalocyanine 36 was

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

• Grzegorz Mlostoń and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221

• . In contrast to the nucleophilic dimethoxycarbene, the formal transfer of the bis(carbomethoxy)carbene from the sulfur ylide 12 to E-1a leads to the cyclopropane derivative 13 [23] (Scheme 4). The reaction was proposed to occur stepwise via the zwiterrionic intermediate 14. Another example of a

• cyclobutanes 26 [20] (Scheme 7). The ratio of the isomers was the same irrespective of the configuration of 1b, indicating a stepwise reaction mechanism. Non-concerted [2 + 2]-cycloadditions were reported to occur between E- and Z-1b and bicyclo[2.1.0]pentene (27) [32]. Whereas in the case of E-1b two

• isomeric homo-Diels–Alder adducts were found in the mixture. [3 + 2]-Cycloadditions (1,3-dipolar cycloadditions) Electron-rich 1,3-dipoles such as thiocarbonyl S-methanides and azomethine ylides react with dipolarophiles E-1 and Z-1 to give five-membered cycloadducts through stepwise zwitterionic reaction

The effect of milling frequency on a mechanochemical organic reaction monitored by in situ Raman spectroscopy

• Patrick A. Julien,
• Ivani Malvestiti and
• Tomislav Friščić

Beilstein J. Org. Chem. 2017, 13, 2160–2168, doi:10.3762/bjoc.13.216

• spectroscopy [30] or by a tandem technique combining these two techniques [31]. Whereas valuable mechanistic information on the course of a milling reaction can be obtained through stepwise, ex situ monitoring [32] based on periodically interrupting the milling process followed by sample extraction and

• , primary assessment of the intensity of the milling process, and it affects the overall impact force, number and rate of impacts of milling media, as well as associated frictional heating. Raman spectroscopy was recently utilized for a stepwise, ex situ assessment of the effect of milling frequency on the

Intramolecular glycosylation

• Xiao G. Jia and
• Alexei V. Demchenko

Beilstein J. Org. Chem. 2017, 13, 2028–2048, doi:10.3762/bjoc.13.201

• ]. Kusumoto et al. clearly demonstrated the advantage of the molecular clamping in application to the synthesis of α-cyclodextrin (Scheme 6) [51]. The tethering was used to improve the selectivity during the stepwise chain elongation via the coupling of maltose building blocks 21 and 22, as well as the