Synthesis and evaluation of new guanidine-thiourea organocatalyst for the nitro-Michael reaction: Theoretical studies on mechanism and enantioselectivity

• Tatyana E. Shubina,
• Matthias Freund,
• Sebastian Schenker,
• Timothy Clark and
• Svetlana B. Tsogoeva

Beilstein J. Org. Chem. 2012, 8, 1485–1498, doi:10.3762/bjoc.8.168

• are in kcal·mol−1, B3PW91/6–31G(d) (first entry), DFT-PCM (second entry), MP2/6–311++G(d,p)//B3PW91/6–31G(d) (third entry), DFT-D (fourth entry). Two possible routes for ternary complex formation. Energies are in kcal·mol−1, B3PW91/6–31G(d) (first entry), DFT-PCM (second entry), MP2/6–311++G(d,p

Interaction of cyclodextrins with pyrene-modified polyacrylamide in a mixed solvent of water and dimethyl sulfoxide as studied by steady-state fluorescence

• Akihito Hashidzume,
• Yongtai Zheng and
• Akira Harada

Beilstein J. Org. Chem. 2012, 8, 1312–1317, doi:10.3762/bjoc.8.150

• pAAmPy. For the β-CD/pAAmPy system (Figure 3a), I480/I376 decreases with increasing [CD]0 at xDMSO = 0.1–0.6. For the γ-CD/pAAmPy system (Figure 3b), on the other hand, I480/I376 increases with [CD]0 at xDMSO = 0–0.2. Discussion Detailed study of the equilibria of the inclusion complex formation of CDs

• described in the Supporting Information File 1, the concentrations of all species can be calculated by using the equilibrium constant (Kβ) for the inclusion complex formation, and I480/I376 can be also obtained as given in Equation 3. Here [Py], [Py°], [CD], [CD·Py], and [CD·Py°] denote the concentrations

• inclusion complex formation, and I480/I376 can be also obtained as given in Equation 4. Here [CD·Py2] denotes the concentration of the complex of CD with Py2, and A'2,480 is a constant. It is also likely that A2,376 = A'2,376 = 0. When Kγ and A'2,480/A1,376 are chosen appropriately, the I480/I376 values

Synthesis of mesomeric betaine compounds with imidazolium-enolate structure

• Nina Gonsior,
• Fabian Mohr and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 390–397, doi:10.3762/bjoc.8.42

• ). Regarding our interest in supramolecular chemistry and the enhancement of water solubility, the ability of 3 to form inclusion complexes with randomly methylated (1.8) β-cyclodextrin (m-β-CD) was investigated by means of UV–vis spectroscopy. Therefore, the type of inclusion complex and the complex formation

Fifty years of oxacalix[3]arenes: A review

• Kevin Cottet,
• Paula M. Marcos and
• Peter J. Cragg

Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22

• to a combination of several factors, of which host–C60 complex formation is only one [77]. Consequently, reported Kassoc values determined by this method should be treated with some caution. Fullerene derivatives that lack some of the symmetry of the parent compound have been shown to bind to

Efficient, highly diastereoselective MS 4 Å-promoted one-pot, three-component synthesis of 2,6-disubstituted-4-tosyloxytetrahydropyrans via Prins cyclization

• Naseem Ahmed and
• Naveen Kumar Konduru

Beilstein J. Org. Chem. 2012, 8, 177–185, doi:10.3762/bjoc.8.19

• . Then, an intramolecular nucleophilic attack of the double bond in the oxo-carbenium ion led to cyclization and charge transfer complex formation with the tosylate group to afford the 2,6-disubstituted-4-tosyloxytetrahydropyran (Scheme 2). All structures of the 2,6-disubstituted-4

Thermodynamic and kinetic stabilization of divanadate in the monovanadate/divanadate equilibrium using a Zn-cyclene derivative: Towards a simple ATP synthase model

• Hanno Sell,
• Anika Gehl,
• Frank D. Sönnichsen and
• Rainer Herges

Beilstein J. Org. Chem. 2012, 8, 81–89, doi:10.3762/bjoc.8.8

• complex formation model. This model was refined with respect to the experimental data. In the approach mentioned above, the equilibria of the multi component system were described mathematically by mass balance equations. When the equilibrium species are written with H+, VO43−, and Zn-benzylcyclene 1 as

• is mainly due to the fact that the free binding enthalpy of ligand 1 to divanadate is 13.7 kJ mol−1 larger than the complex formation with monovanadate. Complexation with 1 also favors the formation of divanadate kinetically by decreasing its rate of hydrolysis from 164 s−1 to 70 s−1 upon addition of

Highly efficient cyclosarin degradation mediated by a β-cyclodextrin derivative containing an oxime-derived substituent

• Michael Zengerle,
• Florian Brandhuber,
• Christian Schneider,
• Franz Worek,
• Georg Reiter and
• Stefan Kubik

Beilstein J. Org. Chem. 2011, 7, 1543–1554, doi:10.3762/bjoc.7.182

• follow a common design principle, involving three distinct subunits each of which has a characteristic function (Figure 1): A cyclodextrin ring, which forms the basis of each compound. Complex formation between this subunit and the substrate should bring the P-atom of the substrate into spatial proximity

NMR studies of anion-induced conformational changes in diindolylureas and diindolylthioureas

• Damjan Makuc,
• Jennifer R. Hiscock,
• Mark E. Light,
• Philip A. Gale and
• Janez Plavec

Beilstein J. Org. Chem. 2011, 7, 1205–1214, doi:10.3762/bjoc.7.140

• urea analogues, such as 1, this is accompanied by higher order complex formation with oxo-anions in the solid state. For example, with dihydrogen phosphate, three equivalents of receptor complex to a single anion, which has doubly deprotonated, resulting in the formation of a complex in which twelve

Synthesis of 5-(2-methoxy-1-naphthyl)- and 5-[2-(methoxymethyl)-1-naphthyl]-11H-benzo[b]fluorene as 2,2'-disubstituted 1,1'-binaphthyls via benzannulated enyne–allenes

• Yu-Hsuan Wang,
• Joshua F. Bailey,
• Jeffrey L. Petersen and
• Kung K. Wang

Beilstein J. Org. Chem. 2011, 7, 496–502, doi:10.3762/bjoc.7.58

• allow these compounds to serve as hetero-bidentate ligands for complex formation with transition metals [20]. We also investigated the possibility of using the benzannulated enediynes bearing a 1-naphthyl, a 2-methoxy-1-naphthyl, or a 2-(methoxymethyl)-1-naphthyl substituent at one of the alkynyl

Effects of anion complexation on the photoreactivity of bisureido- and bisthioureido-substituted dibenzobarrelene derivatives

• Heiko Ihmels and
• Jia Luo

Beilstein J. Org. Chem. 2011, 7, 278–289, doi:10.3762/bjoc.7.37

• spectrometry. To assess whether the influence of the anions on the photoreactivity of the dibenzobarellenes is caused by complex formation, the propensity of the urea and thiourea functionalities to associate with anions was investigated by spectrophotometric titrations of selected tetrabutylammonium salts

• corresponding Job plot confirms the 1:1 complex between 1h and SMD (Supporting Information File 1). Moreover, complex formation was confirmed by a weak NOE effect, as determined by ROESY NMR experiments, between the protons in the ortho position of the phenyl group of the mandelate and the bis(trifluoro)phenyl

• reaction time of the DPM rearrangement of the ureido-substituted derivative 1h upon association with anions. Since the photometric titrations clearly indicate complex formation, it may be assumed that the decreased reaction times are due to restricted molecular flexibility of the ureido- and thioureido

Palladium-catalyzed formation of oxazolidinones from biscarbamates: a mechanistic study

• Benan Kilbas and
• Metin Balci

Beilstein J. Org. Chem. 2011, 7, 246–253, doi:10.3762/bjoc.7.33

• proposed mechanism of oxazolidinone formation [3], the first step is complex formation between the metal and olefin. Steric and electronic effects of the olefin determine the stability of the complex. For example, bulky groups decrease the stability of the complex via steric interactions, while electron

Chiral recognition of macromolecules with cyclodextrins: pH- and thermosensitive copolymers from N-isopropylacrylamide and N-acryloyl-D/L-phenylalanine and their inclusion complexes with cyclodextrins

• Sabrina Gingter,
• Ella Bezdushna and
• Helmut Ritter

Beilstein J. Org. Chem. 2011, 7, 204–209, doi:10.3762/bjoc.7.27

• ROESY experiment showing the correlation between protons of the phenyl moiety of 4D with the β-CD protons. NMR shifts of the complexed monomer 2D. Comparison of 1H NMR spectra of 2D and 2L complexed with β-CD. Complex formation with phenolphthalein and phenylalanine as competitor. Hydrodynamic diameters

Conjugated polymers containing diketopyrrolopyrrole units in the main chain

• Bernd Tieke,
• A. Raman Rabindranath,
• Kai Zhang and
• Yu Zhu

Beilstein J. Org. Chem. 2010, 6, 830–845, doi:10.3762/bjoc.6.92

• -derivative upon complex formation with polyallylamine hydrochloride or polyethyleneimine [24]. The complexes exhibit a mesomorphous structure with the glass transition temperatures dependent on the structure of the polyelectrolyte. The first synthesis of conjugated DPP-polymers and copolymers via Pd

Calix[4]arene-click-cyclodextrin and supramolecular structures with watersoluble NIPAAM-copolymers bearing adamantyl units: “Rings on ring on chain”

• Bernd Garska,
• Monir Tabatabai and
• Helmut Ritter

Beilstein J. Org. Chem. 2010, 6, 784–788, doi:10.3762/bjoc.6.83

• supramolecular complex formation with poly(NIPAAM) bearing attached adamantyl units was investigated by dynamic light scattering (DLS) and turbidity measurements. Keywords: β-cyclodextrin; calix[4]arene; click chemistry; poly(NIPAAM); Introduction Supramolecular interactions of macrocycles with different types

Chromo- and fluorophoric water-soluble polymers and silica particles by nucleophilic substitution reaction of poly(vinyl amine)

• Katja Hofmann,
• Ingolf Kahle,
• Frank Simon and
• Stefan Spange

Beilstein J. Org. Chem. 2010, 6, No. 79, doi:10.3762/bjoc.6.79

• , 1645, 1576, 1549; C15H6N2O (230.23) Anal. calcd. C, 78.26; H, 2.63; N, 12.17; found C, 77.96; H, 2.61; N, 11.79. Fluorophoric, carbonitrile-functionalized PVAm (1-P) For the β-cyclodextrin complex formation, stoichiometric amounts of 1 (0.29 g, 1.28 mmol) and β-DMCD (1.68 g, 1.28 mmol) were dissolved

RAFT polymers for protein recognition

• Alan F. Tominey,
• Julia Liese,
• Sun Wei,
• Klaus Kowski,
• Thomas Schrader and
• Arno Kraft

Beilstein J. Org. Chem. 2010, 6, No. 66, doi:10.3762/bjoc.6.66

• major trends gained from spectroscopic detection but differed in several details (Table 2). Specifically, RAFT copolymers S10CH10, S10BN10, S10OC10, S10CH15 and S20CH15 were examined in their complex formation with cytochrome C (MW 14 kD, pI 9.2) and hemoglobin (MW 68 kD, pI 7.0). Negligible heat

• -containing RAFT copolymer and lysine–rich histone (Kd = 16 nM). In the future, we intend to investigate if it is possible to interrupt the nucleosome complex formation by noncovalent detachment of ds-DNA from its “own” histone proteins using histone-binding RAFT copolymers. Structures of monomers 1–7 and

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

• solvents building strong hydrogen bonds or having electrostatic and charge-transfer capabilities interfere with the ammonium ion binding and may even completely inhibit the complex formation. Recognition in water is especially a challenging topic of growing interest and has been recently reviewed [36

• sites. Differences between these types of ligands also show up in the kinetics of complex formation. The conformationally rigid cryptands complex slower than coronands and these in turn are slower than the flexible podands. In contrast to crown ethers, the three dimensional cryptands display peak

Ring opening metathesis polymerization-derived block copolymers bearing chelating ligands: synthesis, metal immobilization and use in hydroformylation under micellar conditions

• Gajanan M. Pawar,
• Jochen Weckesser,
• Siegfried Blechert and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2010, 6, No. 28, doi:10.3762/bjoc.6.28

• formation of a mono-dipyridyl-Rh(I) complex as observed for M1) [9]. Consequently, almost 90% of the dipyrid-2-ylamide ligands were not involved in complex formation, which is of importance for the catalytic behavior of the supported catalyst and for metal leaching. Poly(M1-b-M2)-Rh was again subject to cmc

Templated versus non-templated synthesis of benzo-21-crown-7 and the influence of substituents on its complexing properties

• Wei Jiang and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2010, 6, No. 14, doi:10.3762/bjoc.6.14

• the phenyl group in 5-H•PF6 is too bulky to thread through the cavity of C7 [23]. Complex formation thus immediately indicates that the crown ether must have a larger cavity than C7. As seen in Figure 1b, the spectra of the equimolar mixture of 5-H•PF6 and C7 is the simple superimposition of their

• individual spectra (Figure 1a,Figure 1c). However, addition of 5-H•PF6 to the fraction containing the larger oligomers 2-(n) caused shifts of all signals for both of guest and host indicative of complex formation (Figure 1d,Figure 1e). From these experiments, we can conclude that crown ethers larger than C7

Recognition properties of receptors consisting of imidazole and indole recognition units towards carbohydrates

• Monika Mazik and
• André Hartmann

Beilstein J. Org. Chem. 2010, 6, No. 9, doi:10.3762/bjoc.6.9

• equiv of the receptor, indicating important contribution of the OH groups of 6a to the complex formation. Furthermore, the addition of 4 or 5 to a CDCl3 solution of β-glucoside 6a caused significant upfield shift of the CH signals of 6a, indicating the participation of the sugar CH units in the

An enantiomerically pure siderophore type ligand for the diastereoselective 1 : 1 complexation of lanthanide(III) ions

• Markus Albrecht,
• Olga Osetska,
• Thomas Abel,
• Gebhard Haberhauer and
• Eva Ziegler

Beilstein J. Org. Chem. 2009, 5, No. 78, doi:10.3762/bjoc.5.78

• facile synthesis of a highly preorganized tripodal enterobactine-type ligand 1a-H3 consisting of a chiral C3-symmetric macrocyclic peptide and three tridentate 2-amido-8-hydroxyquinoline coordinating units is presented. Complex formation with various metal ions (Al3+, Ga3+, Fe3+, La3+ and Eu3+) was

• described dissociation equilibrium in solution uncoordinated ligand can be observed as well at m/z = 1464.9 {K(1a-H3)}+. UV and CD titration experiments As a sensitive technique for the investigation of the complex formation of ligand 1a-H3 with a series of trivalent metal ions we performed UV–vis as well

• simplification reduces the number of optimization steps in the calculations and should not affect the extent of diastereoselectivity for the complex formation. In principle the C3-symmetric 1b·La complex can adopt four different conformations (Λ1, Λ2, Δ1, Δ2): The 8-hydroxyquinoline units can be present in two

An efficient synthesis of novel pyrano[2,3-d]- and furopyrano[2,3-d]pyrimidines via indium- catalyzed multi- component domino reaction

• Dipak Prajapati and
• Mukut Gohain

Beilstein J. Org. Chem. 2006, 2, No. 11, doi:10.1186/1860-5397-2-11

• %). Introduction The emergence of indium(III) compounds as efficient Lewis acid catalysts presents new and exciting opportunities for organoindium chemistry. [1][2] It was found that the low reactivity of trivalent organoindium reagents can be increased by complex formation with organolithium compounds.[3] The