Amino-functionalized (meth)acryl polymers by use of a solvent-polarity sensitive protecting group (Br-t-BOC)

• Helmut Ritter,
• Monir Tabatabai and
• Markus Herrmann

Beilstein J. Org. Chem. 2016, 12, 245–252, doi:10.3762/bjoc.12.26

• , IR, GPC and DSC methods. The kinetics of the deprotection step was followed by 1H NMR spectroscopy. The solvent polarity and neighboring group effects on the kinetics of deprotection are discussed. Keywords: amino group protection; bromo-tert-butyloxycarbonyl; deprotection; free radical

• polymerization; (meth)acryl polymers; neighboring group effects; solvent polarity; Introduction Amino groups are important functionalities in polymer chemistry, e.g., for hardening various epoxy resins [1]. However, they easily react in an undesired side reaction with electron-poor double bonds of (meth

• this in mind, the bromo-tert-butyloxycarbonyl (Br-t-BOC) group represents the first known solvent-polarity sensitive amino-protecting group. As shown in Figure 1, this group is stable in nonpolar solvents because of high activation energy and easily decomposes in a more polar environment because of

Friedel–Crafts-type reaction of pyrene with diethyl 1-(isothiocyanato)alkylphosphonates. Efficient synthesis of highly fluorescent diethyl 1-(pyrene-1-carboxamido)alkylphosphonates and 1-(pyrene-1-carboxamido)methylphosphonic acid

• Anna Wrona-Piotrowicz,
• Janusz Zakrzewski,
• Anna Gajda,
• Tadeusz Gajda,
• Anna Makal,
• Arnaud Brosseau and
• Rémi Métivier

Beilstein J. Org. Chem. 2015, 11, 2451–2458, doi:10.3762/bjoc.11.266

• practically did not influence the electronic absorption and emission spectra. Structured emission bands were observed showing only a small effect of solvent polarity (Figure 1). However, the fluorescence quantum yields of 3a–d and 4 were significantly higher than that of 5. In order to explain this phenomenon

Why base-catalyzed isomerization of N-propargyl amides yields mostly allenamides rather than ynamides

• Armando Navarro-Vázquez

Beilstein J. Org. Chem. 2015, 11, 1441–1446, doi:10.3762/bjoc.11.156

• ). Nonetheless, the above results suggest that varying the reaction conditions (perhaps solvent polarity) could eventually lead to the observation of the allenimides. NMR deuteration studies could be of help to experimentally eliminate possible kinetic effects in the observed lack of reactivity [19]. Having

Microsolvation and sp²-stereoinversion of monomeric α-(2,6-di-tert-butylphenyl)vinyllithium as measured by NMR

• Rudolf Knorr,
• Monika Knittl and
• Eva C. Rossmann

Beilstein J. Org. Chem. 2014, 10, 2521–2530, doi:10.3762/bjoc.10.263

• place of 47%) THF solution (−8 °C in Table S2, [15]); however, this weak acceleration might also be due to the increased solvent polarity. The pseudomonomolecular, ionic mechanism in Scheme 3 had previously [11] been deduced through finding a Hammett reaction constant of ρ = +5.2 for the sp2

Scalable synthesis of 5,11-diethynylated indeno[1,2-b]fluorene-6,12-diones and exploration of their solid state packing

• Bradley D. Rose,
• Peter J. Santa Maria,
• Aaron G. Fix,
• Chris L. Vonnegut,
• Lev N. Zakharov,
• Sean R. Parkin and
• Michael M. Haley

Beilstein J. Org. Chem. 2014, 10, 2122–2130, doi:10.3762/bjoc.10.219

• different in polar solvents when compared to non-polar solvents, thus leading to an energy shift of this transition. Likewise if the S0→S1 transition was a π→π* there should be essentially no change in the transition energy when changing solvent polarity. We found that the shift in the spectrum upon

• changing solvent polarity in going from n-hexane to acetone was 0.02 eV, supporting our hypothesis that the 450–550 nm absorption is indeed a π→π* transition as indicated by calculations. X-ray crystallography. We explored the solid-state packing geometries resulting from altering the substitution on the

Photo, thermal and chemical degradation of riboflavin

• Muhammad Ali Sheraz,
• Sadia Hafeez Kazi,
• Sofia Ahmed,
• Zubair Anwar and
• Iqbal Ahmad

Beilstein J. Org. Chem. 2014, 10, 1999–2012, doi:10.3762/bjoc.10.208

• been identified that affect the stability of RF. These factors include radiation source, its intensity and wavelength, pH, presence of oxygen, buffer concentration and ionic strength, solvent polarity and viscosity, and use of stabilizers and complexing agents. A detailed review of the literature in

• concentration (0.2–1.0 M) in the pH range of 4.0–7.0 (Figure 8). The trivalent citrate ions were found to have a greater inhibitory effect on the photolysis of RF as compared to the divalent citrate ions probably due to the quenching of the excited triplet state of RF [31]. Effect of solvent polarity and

• viscosity The rate of RF photolysis is affected by solvent polarity, which causes changes in the conformation of the ribityl side chain to undergo degradation [83]. RF shows higher photostability in less polar solvents [96]. When RF was irradiated anaerobically in alcohols and alcohol/water mixtures, a

cis–trans Isomerization of silybins A and B

• Michaela Novotná,
• Radek Gažák,
• David Biedermann,
• Florent Di Meo,
• Petr Marhol,
• Marek Kuzma,
• Lucie Bednárová,
• Kateřina Fuksová,
• Patrick Trouillas and
• Vladimír Křen

Beilstein J. Org. Chem. 2014, 10, 1047–1063, doi:10.3762/bjoc.10.105

• EtOAc) and acids (η = 7.3 eV in EtOAc), respectively (Table 2), favoring such a coordinate bond. The hardness of BF3 and silybin A is not significantly modified when the solvent polarity is increased (Table 2). The hardness of silybin B was not calculated, as the stereochemistry is not expected to

• study the impact of the solvent polarity on the HSAB principle. The hardness of BF3 and silybin A is not significantly modified when the solvent polarity is increased (Table 2). New methods to rationalize chemical reactivity have been developed in the field of quantum mechanical methods over the past

The Ugi four-component reaction as a concise modular synthetic tool for photo-induced electron transfer donor-anthraquinone dyads

• Sarah Bay,
• Gamall Makhloufi,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 1006–1016, doi:10.3762/bjoc.10.100

• term of the solvent polarity and the effect of the distance of the donor and acceptor moieties according to Indeed, for all Do-anthraquinone dyads 8 exergonic Gibbs free energies for the electron transfer are found, both for the simplified free enthalpy ΔGET,simpl, i.e., the first two terms of

On the mechanism of photocatalytic reactions with eosin Y

• Michal Majek,
• Fabiana Filace and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97

• discussed on the basis of pH, solvent polarity, lamp type, absorption properties, and quantum yields. Determination of the latter proved to be an especially valuable tool for the distinction between radical chain and photocatalytic reactions. Keywords: mechanism; organocatalysis; photocatalysis; photoredox

Chromatographically separable rotamers of an unhindered amide

• Mario Geffe,
• Lars Andernach,
• Oliver Trapp and
• Till Opatz

Beilstein J. Org. Chem. 2014, 10, 701–706, doi:10.3762/bjoc.10.63

• for this overestimation may be an inappropriate representation of the global solvation by the COSMO model or the limited double-zeta basis set, the substitution of which by a larger triple-zeta basis set is too expensive in terms of computational time. Increasing the solvent polarity in COSMO up to

Conformation of dehydropentapeptides containing four achiral amino acid residues – controlling the role of L-valine

• Michał Jewgiński,
• Joanna Krzciuk-Gula,
• Maciej Makowski,
• Rafał Latajka and
• Paweł Kafarski

Beilstein J. Org. Chem. 2014, 10, 660–666, doi:10.3762/bjoc.10.58

• increase in solvent polarity promotes more ordered conformations of hexapeptides containing two dehydrophenylalanine residues [38]. On the other hand, Inai and co-workers showed that in the case of dehydropeptides containing only one chiral L-residue in the N-terminal position of the peptide a left-handed

• helical conformation is adopted regardless of the solvent polarity [39], but when a chiral residue occupied the second position of the peptide, the screw sense of the helix depends on the type of solvent [40]. Conclusion The conformational studies in solution performed by NMR spectroscopy show that all

Structure of 1,5-benzodiazepinones in the solid state and in solution: Effect of the fluorination in the six-membered ring

• Marta Pérez-Torralba,
• Rosa M. Claramunt,
• M. Ángeles García,
• Concepción López,
• M. Carmen Torralba,
• M. Rosario Torres,
• Ibon Alkorta and
• José Elguero

Beilstein J. Org. Chem. 2013, 9, 2156–2167, doi:10.3762/bjoc.9.253

• = 5, R2 = 0.993. This equation predicts for 4a 61.0 kJ mol−1. Note the increase between toluene and DMSO that corresponds to the raise of inversion barriers with that of the solvent polarity; a similar behavior has been reported for diazepam (7-chloro-1,3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin

Self-assembly of 2,3-dihydroxycholestane steroids into supramolecular organogels as a soft template for the in-situ generation of silicate nanomaterials

• Valeria C. Edelsztein,
• Andrea S. Mac Cormack,
• Matías Ciarlantini and
• Pablo H. Di Chenna

Beilstein J. Org. Chem. 2013, 9, 1826–1836, doi:10.3762/bjoc.9.213

• separately the hydrogen-bond donor (HBD, α), hydrogen-bond acceptor (HBA, β), and polarizability (π*) properties as contributions to the overall solvent polarity had also been occasionally used to study solvent–gelator specific interactions [20][21]. LMOGs based on cholesterol and bile acids offered the most

Synthesis and spectroscopic properties of 4-amino-1,8-naphthalimide derivatives involving the carboxylic group: a new molecular probe for ZnO nanoparticles with unusual fluorescence features

• Laura Bekere,
• David Gachet,
• Vladimir Lokshin,
• Wladimir Marine and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2013, 9, 1311–1318, doi:10.3762/bjoc.9.147

• fluorescence maxima at 397 and 401 nm, respectively. In contrast, the spectroscopic properties of derivatives 3 and 4 depend on the solvent polarity. The absorption and fluorescence maxima of 4 in different solvents are collated in Table 2 and the typical spectra are shown in Figure 1. The observed

A new synthetic protocol for coumarin amino acid

• Xinyi Xu,
• Xiaosong Hu and
• Jiangyun Wang

Beilstein J. Org. Chem. 2013, 9, 254–259, doi:10.3762/bjoc.9.30

• coumarin amino acid 1a (Figure 1) is sensitive to both pH and solvent polarity, which makes it a good probe to investigate protein functionalities and biological processes related to them. The following examples are several applications of it. Shan and co-workers used compound 1a to form a FRET pair with

• cannot be achieved by using GFP labeling technique since GFP is relatively insensitive to the pH and the solvent polarity of the solution. Many more examples of the usage of 1a have also been reported [5][6][7][8]. Due to the high importance of 1a, there has been a great need for a highly efficient and

• different sensitivities to pH and solvent polarity, and can serve as new fluorescent probes in a variety of applications. Results and Discussion Scheme 1 gives an outline of the new protocol used to synthesize compound 1. First, the coumarin ring with a 4-chloromethyl group (compound 3) was formed through

Asymmetric desymmetrization of meso-diols by C₂-symmetric chiral 4-pyrrolidinopyridines

• Hartmut Schedel,
• Keizo Kan,
• Yoshihiro Ueda,
• Kenji Mishiro,
• Keisuke Yoshida,
• Takumi Furuta and
• Takeo Kawabata

Beilstein J. Org. Chem. 2012, 8, 1778–1787, doi:10.3762/bjoc.8.203

• isobutyric anhydride in the presence of catalyst 12b (Table 2, entries 1–5). A clear relationship between the enantioselectivity and the solvent polarity was observed: The lower the polarity of the solvent, the higher the enantioselectivity. This suggests that the hydrogen-bonding interaction between the

Liquid-crystalline nanoparticles: Hybrid design and mesophase structures

• Gareth L. Nealon,
• Romain Greget,
• Cristina Dominguez,
• Zsuzsanna T. Nagy,
• Daniel Guillon,
• Jean-Louis Gallani and
• Bertrand Donnio

Beilstein J. Org. Chem. 2012, 8, 349–370, doi:10.3762/bjoc.8.39

• , squarelike and stripelike arrangements as a function of both the length of the tethering group and the solvent polarity (Figure 26). These results bode well for the use of these discotic materials in NP self-organisation, and it appears only a matter of time before LC phases are observed for discrete hybrids

The interplay of configuration and conformation in helical perylenequinones: Insights from chirality induction in liquid crystals and calculations

• Elisa Frezza,
• Silvia Pieraccini,
• Stefania Mazzini,
• Alberta Ferrarini and
• Gian Piero Spada

Beilstein J. Org. Chem. 2012, 8, 155–163, doi:10.3762/bjoc.8.16

• moment than those of cercosporin (1), therefore 2 should be more sensitive to solvent polarity (acetone has a dielectric constant of about 20 at room temperature). HTP predictions by the SC method Within the SC approach, the HTP of a chiral dopant in a nematic solvent is proportional to the so-called

Fluorescent hexaaryl- and hexa-heteroaryl[3]radialenes: Synthesis, structures, and properties

• Antonio Avellaneda,
• Courtney A. Hollis,
• Xin He and
• Christopher J. Sumby

Beilstein J. Org. Chem. 2012, 8, 71–80, doi:10.3762/bjoc.8.7

• (~0.04 mM) indicates that 1 – which has 12 methyl substituents arranged above and below the [3]radialene core – aggregates in the more polar acetone solvent (polarity index for dichloromethane 3.1; acetone 5.1). The less hydrophobic [3]radialenes, 2 and 3, do not show the same behaviour. The more

Valence isomerization of cyclohepta-1,3,5-triene and its heteroelement analogues

• Helen Jansen,
• J. Chris Slootweg and
• Koop Lammertsma

Beilstein J. Org. Chem. 2011, 7, 1713–1721, doi:10.3762/bjoc.7.201

• methyl groups in benzene oxide (4) [38][40][51]. Thus, in contrast to the cycloheptatriene–norcaradiene (1–2) pair, the equilibrium constant for oxepine (3) and bicyclic benzene oxide (4) varies widely with solvent polarity and to some extent with temperature and substituents, making it possible to work

Synthesis of dye/fluorescent functionalized dendrons based on cyclotriphosphazene

• Aurélien Hameau,
• Sabine Fuchs,
• Régis Laurent,
• Jean-Pierre Majoral and
• Anne-Marie Caminade

Beilstein J. Org. Chem. 2011, 7, 1577–1583, doi:10.3762/bjoc.7.186

• or in pyridine, and was ascribed to the solvent polarity, which modifies the interactions between both parts of the molecule [17]. In our case, we may consider that the structure of dendron 10 in solution in dioxane is more expanded than in water, which should bring the hydrophobic moieties (the

Predicting the UV–vis spectra of oxazine dyes

• Scott Fleming,
• Andrew Mills and
• Tell Tuttle

Beilstein J. Org. Chem. 2011, 7, 432–441, doi:10.3762/bjoc.7.56

• been observed and the mechanism(s) explored in previous studies by various authors [9][10][11]. Most of these investigations have involved measuring experimentally the spectroscopic features of oxazine dyes, upon varying the solvent polarity. However, some attempt has been made to rationalize these

• observations by a computational study of the solvatochromism of the oxazine dye Nile red [12]. In the investigation, TD-DFT was applied in order to try and explore the contributing factors in the solvatochromism observed with Nile red, upon gradually increasing the solvent polarity from benzene to acetonitrile

Formation of macrocyclic lactones in the Paternò–Büchi dimerization reaction

• Junya Arimura,
• Tsutomu Mizuta,
• Yoshikazu Hiraga and
• Manabu Abe

Beilstein J. Org. Chem. 2011, 7, 265–269, doi:10.3762/bjoc.7.35

• detected by 1H NMR (500 MHz). To investigate the medium effect on the formation of 2a, the photochemical reaction of 1a was performed in several solvents (entries 4–6). The yield of 2a decreased with increasing solvent polarity; 16% in toluene (entry 4) and 10% in CH3CN (entry 6). Temperature had no effect

Fluorometric recognition of both dihydrogen phosphate and iodide by a new flexible anthracene linked benzimidazolium-based receptor

• Kumaresh Ghosh and
• Debasis Kar

Beilstein J. Org. Chem. 2011, 7, 254–264, doi:10.3762/bjoc.7.34

• in emission in CHCl3 containing 0.1% CH3CN (Supporting Information File 1). These observations thus intimate that solvent polarity is an important aspect for monitoring the sensing behavior of benzimidazolium-based receptors. In our opinion, CH3CN in the present case participates in H-bonding with

Donor-acceptor substituted phenylethynyltriphenylenes – excited state intramolecular charge transfer, solvatochromic absorption and fluorescence emission

• Ritesh Nandy and
• Sethuraman Sankararaman

Beilstein J. Org. Chem. 2010, 6, 992–1001, doi:10.3762/bjoc.6.112

• absorption and fluorescence emission properties of these molecules have been studied in solvents of different polarity. For a given derivative, solvent polarity had minimal effect on the absorption maxima. However, for a given solvent the absorption maxima red shifted with increasing conjugation of the

• substituent. The fluorescence emission of these derivatives was very sensitive to solvent polarity. In the presence of strongly electron withdrawing (–CN) and strongly electron donating (–NMe2) substituents large Stokes shifts (up to 130 nm, 7828 cm−1) were observed in DMSO. In the presence of carbonyl

• whose fluorescence emission is sensitive to environment and solvent polarity are of significant interest due to their versatile applications in chemistry, biology and environmental science [1][2][3][4]. Considerable effort has been expended into shifting the fluorescence emission of organic molecules