Constrained thermoresponsive polymers – new insights into fundamentals and applications

• Patricia Flemming,
• Alexander S. Münch,
• Andreas Fery and
• Petra Uhlmann

Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138

• function of composition. This region cannot be realized by “equilibrium” experiments and can only be captured mathematically. These points are also called spinodal points. In addition, two further minima exist. By applying the double tangent to these two points C and D, the composition of the coexisting

A study on selective transformation of norbornadiene into fluorinated cyclopentane-fused isoxazolines

• Zsanett Benke,
• Attila M. Remete and
• Loránd Kiss

Beilstein J. Org. Chem. 2021, 17, 2051–2066, doi:10.3762/bjoc.17.132

• across ROM or ROCM into a variety of alkenylated, functionalized scaffolds [22][23][24][25][26][27][28][29][30][31][32][33][34]. Although metathesis is a reversible process, it is often shifted towards a certain direction. For example, the equilibrium of the reaction of ethylene with a strained ring

Regioselective N-alkylation of the 1H-indazole scaffold; ring substituent and N-alkylating reagent effects on regioisomeric distribution

• Ryan M. Alam and
• John J. Keating

Beilstein J. Org. Chem. 2021, 17, 1939–1951, doi:10.3762/bjoc.17.127

• -1 alkylation of the exemplar methyl ester 9 and other appropriately C-3 substituted indazoles (19, or 21–24) (under conditions A, Table 1, entry 22) involves the initial irreversible deprotonation of the indazole in the presence of NaH to initially give indazolyl salt 65 which is in equilibrium with

Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

• Susanne M. Fischer,
• Simon Renner,
• A. Daniel Boese and
• Christian Slugovc

Beilstein J. Org. Chem. 2021, 17, 1689–1697, doi:10.3762/bjoc.17.117

• , in this case, the activity of the catalyst is not rate determining. This observation is rationalized by the occurrence of a non-productive acid–base equilibrium involving the de- and re-protonation of the considerably acidic alkyne proton in d (pKa = 15.61 [20]) [21]. The reaction conditions

• : −85.6 kJ/mol). Consequently, such calculated Michael acceptor affinities correlate with the experimental results and are suited to reflect the actual activity of the phosphines under investigation. This is reasonable because the position of the thermodynamic equilibrium of the unreacted Michael acceptor

2,4-Bis(arylethynyl)-9-chloro-5,6,7,8-tetrahydroacridines: synthesis and photophysical properties

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli,
• Noureddine Chaaben,
• Kamel Alimi,
• Stefan Jopp and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 1629–1640, doi:10.3762/bjoc.17.115

• equilibrium conformer at ground state was first found at AM1 level. Then, further optimizations through density functional theory (DFT) approach [73] at the restricted Becke3–Lee–Yang–Parr hybrid functional (B3LYP) with standard basis set 6-31G were carried out. Experimental procedure and spectroscopic data

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• promote the enolization of carbonyl compounds [43] allowed the use of simple ketones as substrates in the intramolecular hydroalkylation of olefins. As discussed before, these are problematic substrates because of the low equilibrium constant between the keto and enol forms. Che’s group used [IPrAuCl

Breaking paracyclophane: the unexpected formation of non-symmetric disubstituted nitro[2.2]metaparacyclophanes

• Suraj Patel,
• Tyson N. Dais,
• Paul G. Plieger and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2021, 17, 1518–1526, doi:10.3762/bjoc.17.109

• . Reaction of 1 with nitric acid alone led to a surprisingly clean, nitration, albeit by a very slow reaction. As stated earlier, nitration is normally a messy reaction. Presumably, the low concentration of nitronium ion present in equilibrium with the acid promotes a clean reaction without polymerization or

Fritsch–Buttenberg–Wiechell rearrangement of magnesium alkylidene carbenoids leading to the formation of alkynes

• Tsutomu Kimura,
• Koto Sekiguchi,
• Akane Ando and
• Aki Imafuji

Beilstein J. Org. Chem. 2021, 17, 1352–1359, doi:10.3762/bjoc.17.94

• . Geometric isomers of magnesium alkylidene carbenoids are in equilibrium [16], and the 1,2-rearrangement occurs giving the alkynes 4 when the substituent R1 is located trans to the chloro group (Scheme 7b). An exchange of halogen atoms was observed in the reaction of a 1-chlorovinyl p-tolyl sulfoxide with

• alkynes 4. a) 1,2-Rearrangement readily takes place with substrates with trans-oriented Cl-substituent to the migratable group R1. b) Formation of product 4 from geometric cis isomer is possible due to the equilibrium between magnesium alkylidene carbenoids. c) Halogen exchange between a 1-chlorovinyl p

Photoinduced post-modification of graphitic carbon nitride-embedded hydrogels: synthesis of 'hydrophobic hydrogels' and pore substructuring

• Cansu Esen and
• Baris Kumru

Beilstein J. Org. Chem. 2021, 17, 1323–1334, doi:10.3762/bjoc.17.92

• analysis to evaluate the vTA incorporation, and microscopy techniques were employed to examine the impact on their morphology. In terms of applicability, water contact angle measurement, equilibrium swelling ratio analysis, and dye releasing efficiency experiment were also conducted. All hydrogel samples

• to parental HGCM substrate. Employing a diverse set of monomers to HGCM network can have an influence on the swelling properties as well. Regarding this, swelling performances of so-formed networks were examined via swelling process at equilibrium state in various conditions (Figure 6b). The first

• conditions demonstrated similar results, yet significantly lower compared to previous examples. In addition, the error margins of equilibrium swelling behavior were affected by isotropic accretion of polymer networks over the substrate. It is important to underline that the presented polymerization process

Synthesis of 10-O-aryl-substituted berberine derivatives by Chan–Evans–Lam coupling and investigation of their DNA-binding properties

• Peter Jonas Wickhorst,
• Mathilda Blachnik,
• Denisa Lagumdzija and
• Heiko Ihmels

Beilstein J. Org. Chem. 2021, 17, 991–1000, doi:10.3762/bjoc.17.81

• shift of the equilibrium between the [3 + 1] conformer, related to the shoulder at 255 nm [59], and the basket-type conformation of 22AG, assigned to the positive signal at 290 nm and the weak negative band at 260 nm [60][61] in favor of the latter. Hence, these observations showed that the ligands bind

• preferentially to the basket-type quadruplex structure and thereby shift the equilibrium to this form. Furthermore, during all titrations of the derivatives 5a–e to 22AG no clear ICD band was detected, which is usually interpreted as an indication of terminal π stacking of the ligand to the quadruplex structure

Stereoselective synthesis and transformation of pinane-based 2-amino-1,3-diols

• Ákos Bajtel,
• Mounir Raji,
• Matti Haukka,
• Ferenc Fülöp and
• Zsolt Szakonyi

Beilstein J. Org. Chem. 2021, 17, 983–990, doi:10.3762/bjoc.17.80

• -dependent 1H NMR spectroscopic measurement was accomplished, we observed that the equilibrium composition was established rapidly, without any significant change in the ratio of the tautomers. The equilibrium shifting strongly to product 15E can account of the difficulty of the reduction process and the

Metal-free glycosylation with glycosyl fluorides in liquid SO₂

• Krista Gulbe,
• Jevgeņija Lugiņina,
• Edijs Jansons,
• Artis Kinens and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 964–976, doi:10.3762/bjoc.17.78

• equilibrium. Keywords: fluorosulfite; glycosyl fluoride; Lewis acid; liquid sulfur dioxide; metal-free glycosylation; Introduction The glycosylation reaction is still one of the most important and basic synthetic strategies in carbohydrate chemistry that provides access to the various types of

• the stereoselectivity of the glycosylation in liquid SO2 is substrate-controlled and approaches a thermodynamic equilibrium determined by the anomeric effect or interference of both the anomeric effect and the assistance of the neighboring ester-type protecting group. Next, we have also observed that

• the anomerization of the glycosylated products towards their thermodynamic equilibrium is promoted by the species formed during the glycosylation reaction [76]. Thus, when anomerically pure thiomannoside β-3c was subjected to the glycosylation conditions (100 °C, 16 h) in liquid SO2 without any

Kinetics of enzyme-catalysed desymmetrisation of prochiral substrates: product enantiomeric excess is not always constant

• Peter J. Halling

Beilstein J. Org. Chem. 2021, 17, 873–884, doi:10.3762/bjoc.17.73

• reaction proceeds to high conversion. For example, an ee of 0.95 at the start of the reaction can decline to less than 0.5 at 95% of equilibrium conversion, but for different enzyme properties it will remain almost unchanged. For most mechanisms a single function of multiple enzyme rate constants (which

• the equilibrium constant where the enzymatic reaction was not completely irreversible [2]. A limitation of the enzymatic resolution is that the maximum yield of the desired enantiomer is the 50% contained in the starting racemate. This is one reason for the current greater interest in enzymatic

• favoured product are completely absent. In most of the applications the overall reaction is significantly reversible, with an equilibrium constant that is not enormously larger than 1. And in many cases there is a noticeable formation of the less favoured enantiomer, with product ee values of 0.98 or less

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

• electrostatic interaction between carboxylate and iminium moieties undergoes a nucleophilic attack by isocyanide to generate nitrilium ion B. The intramolecular acylation of B forms C followed by Mumm rearrangement results in the formation of the desired products 22. The intermediate D may exist in equilibrium

• as depicted in Scheme 56 wherein cycloketone 141 in presence of AcOH exists in equilibrium with enol form B. The imine intermediate A (condensation of aldehyde and pyrazolylamine) surrenders to a [4 + 2] cycloaddition with the enol form B and result in cycloaddition adduct C. A further dehydration

Synthesis of β-triazolylenones via metal-free desulfonylative alkylation of N-tosyl-1,2,3-triazoles

• Soumyaranjan Pati,
• Renata G. Almeida,
• Eufrânio N. da Silva Júnior and
• Irishi N. N. Namboothiri

Beilstein J. Org. Chem. 2021, 17, 762–770, doi:10.3762/bjoc.17.66

• of dimedone (2d). Unlike cyclic 1,3-dicarbonyls, the acyclic 1,3-dicarbonyls possess intramolecular hydrogen bonding and are in rapid equilibrium with their keto-form. In polar solvents, the stability of the enol form is further decreased and, therefore, the keto-enol equilibrium lies more towards

α,γ-Dioxygenated amides via tandem Brook rearrangement/radical oxygenation reactions and their application to syntheses of γ-lactams

• Mikhail K. Klychnikov,
• Radek Pohl,
• Ivana Císařová and
• Ullrich Jahn

Beilstein J. Org. Chem. 2021, 17, 688–704, doi:10.3762/bjoc.17.58

• did not improve the results, indicating that the reactions are at thermodynamic equilibrium after 24 h. Surprisingly, for N-methyl-substituted lactam 12e the diastereomeric enrichment remained rather moderate despite variations of temperature and time (Table 4, entry 5), whereas the diastereomeric

• (Table 4, entries 9–11). Thus, the nitrogen substituent exerted a significant influence on the facility and position of the trans/cis equilibrium of the lactams 12. The influence of an isopropenyl or tetramethylpiperidinyloxymethyl group at C4 has in contrast only little influence on the thermodynamic

• equilibrium (Table 4, entries 7 and 11 vs entries 1 and 9). Attempts to influence the diastereomeric ratio of the cyclization products by irreversible stoichiometric deprotonation of the lactams 12d,f,i by LDA at −78 °C and subsequent protonation by methanol did not lead to substantial changes of the initial

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

• conditions, showing the best combination to be 196 °C, an EG/PET ratio of 2.45:1 (w/w) and a catalyst loading of 0.3 wt % (Table 2, entry 2) [129]. Under these conditions, an equilibrium yield of BHET around 65% was achieved within short reaction times (1 h), much faster than in the absence of catalysts or

Synthesis of (Z)-3-[amino(phenyl)methylidene]-1,3-dihydro-2H-indol-2-ones using an Eschenmoser coupling reaction

• Lukáš Marek,
• Lukáš Kolman,
• Jiří Váňa,
• Jan Svoboda and
• Jiří Hanusek

Beilstein J. Org. Chem. 2021, 17, 527–539, doi:10.3762/bjoc.17.47

• derivatives 9a–e. The substituent R4 strongly influences both the equilibrium between >C=N+HR4 and >C=NR4 as well as the nucleophilic attack of the internal C3 carbanion to give the thiirane intermediate in Scheme 2. While the EWG groups decrease the concentration of the α-thioiminium salt (that is much more

• the equilibrium concentration) of the intermediary α-thioiminium salt which is much more reactive towards an internal nucleophilic attack than the free thioimidate group. Although an electron-withdrawing substituent R4 also enhances the internal nucleophilic attack to both α-thioiminium and imine

Synthesis and physicochemical evaluation of fluorinated lipopeptide precursors of ligands for microbubble targeting

• Masayori Hagimori,
• Estefanía E. Mendoza-Ortega and
• Marie Pierre Krafft

Beilstein J. Org. Chem. 2021, 17, 511–518, doi:10.3762/bjoc.17.45

• interface, with equilibrium surface pressures reaching ≈7–10 mN m−1 versus less than 1 mN m−1 only for their hydrocarbon analog 4. The F-lipopeptides penetrate in the DPPC monolayers in both liquid expanded (LE) and liquid condensed (LC) phases without interfacial film destabilization. By contrast, 4

• , reflecting a progressive adsorption at the interface, then reached a plateau, and stabilized at the equilibrium surface pressure (πeq). The adsorption kinetics demonstrate that the F-lipopeptides formed stable monolayers at the interface. The πeq values increased with the degree of fluorination of the F

Biochemistry of fluoroprolines: the prospect of making fluorine a bioelement

• Vladimir Kubyshkin,
• Rebecca Davis and
• Nediljko Budisa

Beilstein J. Org. Chem. 2021, 17, 439–460, doi:10.3762/bjoc.17.40

• ] and ribonuclease A [140] (Table 3). These results have been explained by considering the conformational bias of the residues (pucker, trans/cis equilibrium), an altered hydrophobicity and polarity and the local environment at the substitution sites. An elevated folding velocity, presumable due to

Identification of volatiles from six marine Celeribacter strains

• Anuj Kumar Chhalodia,
• Jan Rinkel,
• Dorota Konvalinkova,
• Jörn Petersen and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 420–430, doi:10.3762/bjoc.17.38

• from the roseobacter group is the production of the sulfur-containing antibiotic tropodithietic acid (TDA) in Phaeobacter piscinae DSM 103509T [28], a compound that is in equilibrium with its tautomer thiotropocin [29] that was first described from Pseudomonas sp. CB-104 [30]. Its biosynthesis depends

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

Synthesis of legonmycins A and B, C(7a)-hydroxylated bacterial pyrrolizidines

• Wilfred J. M. Lewis,
• David M. Shaw and
• Jeremy Robertson

Beilstein J. Org. Chem. 2021, 17, 334–342, doi:10.3762/bjoc.17.31

• and B, are related as 7a-epimers that interconvert in aqueous solution to form a pH-dependent equilibrium ratio of the two [9]; they are weakly antibacterial and were shown to prolong “the survival period of mice inoculated with leukaemia L-120 cells” [7][8]. Although the clazamycins are not

¹⁹F NMR as a tool in chemical biology

• Diana Gimenez,
• Aoife Phelan,
• Cormac D. Murphy and
• Steven L. Cobb

Beilstein J. Org. Chem. 2021, 17, 293–318, doi:10.3762/bjoc.17.28

• -β2AR, changes in the NMR signals monitored within different helices of the protein revealed that agonist binding primarily shifted the equilibrium towards the G protein-specific active state of helix VI. In contrast, β-arrestin-biased ligands predominantly affected the conformation of specifically

• thermodynamic equilibrium binding constants (K) and kinetic rates of association (kon) and dissociation (koff) in protein–ligand binding events [37]. In order to achieve this, they analysed the binding of four different proline-rich peptides to a 5-FTrp-labelled Src homology 3 (SH3) recognition protein domain

• characterize and quantify the relative populations of monomeric, octameric, and higher oligomer species that populate the pathway from the native PrP state to fibril formation. The equilibrium constants between states were also analysed as a function of both temperature and pressure, allowing to determine the

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• rearrangement of 1,1-difluoro-2-methylenecyclopropane (96) (Scheme 45) [92]. At 210 °C the rate of cleavage of the proximal bond was only 3.8 times faster than for the analogous hydrocarbon. It was also observed that the equilibrium lay significantly in favor of the rearranged product 97, which was by 1.9 kcal