Ambient gold-catalyzed O-vinylation of cyclic 1,3-diketone: A vinyl ether synthesis

• Yumeng Xi,
• Boliang Dong and
• Xiaodong Shi

Beilstein J. Org. Chem. 2013, 9, 2537–2543, doi:10.3762/bjoc.9.288

• -cyclopentadione in DCM at room temperature. Finally and notably, all tested acyclic 1,3-diketones as well as 1,2-diketones gave no O-addition products under the current reaction conditions, likely caused by the intramolecular H-bonding. Conclusion In this letter, we report the first successful gold(I)-catalyzed

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

• affinity is nowadays a vital part of assessing preclinical risks of new drug candidates [73]. The piperidine unit is also incorporated into drugs in order to fulfil more significant tasks, i.e. being part of the pharmacophore itself or providing extended H-bonding networks for improved binding affinities

Spin state switching in iron coordination compounds

• Philipp Gütlich,
• Ana B. Gaspar and
• Yann Garcia

Beilstein J. Org. Chem. 2013, 9, 342–391, doi:10.3762/bjoc.9.39

A new family of four-ring bent-core nematic liquid crystals with highly polar transverse and end groups

• Kalpana Upadhyaya,
• Venkatesh Gude,
• Golam Mohiuddin and
• Rao V. S. Nandiraju

Beilstein J. Org. Chem. 2013, 9, 26–35, doi:10.3762/bjoc.9.4

• unsubstituted benzylidene linkage was preferred due to the presence of the ortho-hydroxy group, which enhances the transverse dipole moment as well as the stability of the imines through intramolecular H-bonding to overcome the hydrolytic instability of the molecules towards moisture. The bent-core platform was

• and elemental analysis. The analytical data are in good agreement with their chemical structures. The main observed FTIR peaks confirmed the intramolecular H-bonding of OH…N at 3184~3186 cm−1, CN stretching at 2220 cm−1, C=O stretching of an ester at 1737~1741 cm−1, C=N stretching of an imine at 1602

Evaluation of a chiral cubane-based Schiff base ligand in asymmetric catalysis reactions

• Kyle F. Biegasiewicz,
• Michelle L. Ingalsbe,
• Jeffrey D. St. Denis,
• James L. Gleason,
• Junming Ho,
• Michelle L. Coote,
• G. Paul Savage and
• Ronny Priefer

Beilstein J. Org. Chem. 2012, 8, 1814–1818, doi:10.3762/bjoc.8.207

• cyclopropanation and Michael addition reactions. Although there was no increase in stereocontrol, upon computational evaluation using both M06L and B3LYP calculations, it was revealed that a pseudo six-membered ring exists, through H-bonding of a cubyl hydrogen to the copper core. This decreases the steric bulk

• are well within the required H-bonding length of <3.2 Å [31]. In addition, the C…Cu lengths of 2.85 and 3.03 Å with M06L and B3LYP, respectively, were well within the required 4.0 Å limit [31]. This produces pseudo six-membered rings having a C–H…Cu bond angle of 125.1° or 122.9° with M06L and B3LYP

• opposed to an intermolecular pseudo-agostic bond. Cubyl hydrogens participating in H-bonding have been reported previously with nitrocubanes [34], as well as with dicubyl vic-disulfone [35]. From the computational results it would appear that the cubes play very little role in blocking either side for

Organocatalytic asymmetric Michael addition of unprotected 3-substituted oxindoles to 1,4-naphthoquinone

• Jin-Sheng Yu,
• Feng Zhou,
• Yun-Lin Liu and
• Jian Zhou

Beilstein J. Org. Chem. 2012, 8, 1360–1365, doi:10.3762/bjoc.8.157

• -phenyloxindole 1a and 1,4-naphthoquinone (2a), with ethyl acetate (EtOAc) as the solvent at 0 °C (Table 1, Figure 1). A variety of bifunctional cinchona alkaloid-derived catalysts 5–9 were first tried, aiming to facilitate the reaction by the dual activation of both reaction partners, with H-bonding donor moiety

Partial thioamide scan on the lipopeptaibiotic trichogin GA IV. Effects on folding and bioactivity

• Marta De Zotti,
• Barbara Biondi,
• Cristina Peggion,
• Matteo De Poli,
• Haleh Fathi,
• Simona Oancea,
• Claudio Toniolo and
• Fernando Formaggio

Beilstein J. Org. Chem. 2012, 8, 1161–1171, doi:10.3762/bjoc.8.129

• ][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44]. Among these properties, we highlight the following: (i) The thioamide NH group is more acidic than that of its oxygenated counterpart and consequently it is a stronger H-bonding donor. (ii) Its cis

Laterally substituted symmetric and nonsymmetric salicylideneimine-based bent-core mesogens

• Sonja Findeisen-Tandel,
• Wolfgang Weissflog,
• Ute Baumeister,
• Gerhard Pelzl,
• H. N. Shreenivasa Murthy and
• Channabasaveshwar V. Yelamaggad

Beilstein J. Org. Chem. 2012, 8, 129–154, doi:10.3762/bjoc.8.15

• group in ortho-position to the CH=N (azomethine) unit not only enhances the photochemical and hydrolytic stability due to intramolecular H-bonding, but also increases the clearing temperature of liquid crystals. Therefore, the introduction of salicylideneimine fragment(s) in the LC molecular

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

• normally filled by the ADP’s adenine in the phosphorylated protein. The indolinone section is located in a deeper pocket with the heteroatoms being involved in H-bonding glutamate and tyrosine residues whilst the pyrrole ring and the diethylaminoethyl appendage are exposed to the solvent environment [8

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

A new fluorescent chemosensor for fluoride anion based on a pyrrole–isoxazole derivative

• Zhipei Yang,
• Kai Zhang,
• Fangbin Gong,
• Shayu Li,
• Jun Chen,
• Jin Shi Ma,
• Lyubov N. Sobenina,
• Albina I. Mikhaleva,
• Guoqiang Yang and
• Boris A. Trofimov

Beilstein J. Org. Chem. 2011, 7, 46–52, doi:10.3762/bjoc.7.8

• -bonding, which is not easy to differentiate from deprotonation of protons on the receptor-NH [4][5]. Some urea/thiourea-containing receptors could particularly recognize Y-shaped oxoanions by H-bonding and more basic anions such as fluoride by deprotonation. Fluoride is primarily used for prevention of

• quenched by only about 33%, i.e., less than that caused by OH−. Considering the stronger basicity of OH−, it preferred to react with receptor 1 by deprotonation rather than by H-bonding [19]. The similar phenomena upon the addition of F− and OH− suggested that receptor 1 recognizes F− in the same way as OH

• reported in recent years, those employing polarized NH groups as anion-binding motifs have attracted considerable attention. Typical examples are charge neutral receptors containing pyrrole, amide, indolocarbazole, guanidium, imidazolium and urea/thiourea moieties. Usually, the anions are recognized via H

Achiral bis-imine in combination with CoCl₂: A remarkable effect on enantioselectivity of lipase-mediated acetylation of racemic secondary alcohol

• K. Arunkumar,
• M. Appi Reddy,
• T. Sravan Kumar,
• B. Vijaya Kumar,
• K. B. Chandrasekhar,
• P. Rajender Kumar and
• Manojit Pal

Beilstein J. Org. Chem. 2010, 6, 1174–1179, doi:10.3762/bjoc.6.134

• reaction was complete within 12 h. The absolute configuration of the resolved chiral alcohol and its acetate was in accordance with Kazlauskas’ rule [25] (see Supporting Information File 1 for optical rotation values). Mechanistically [12], the special H-bonding rearrangement of the “catalytic triad” (i.e

Self-assembly and semiconductivity of an oligothiophene supergelator

• Pampa Pratihar,
• Suhrit Ghosh,
• Vladimir Stepanenko,
• Sameer Patwardhan,
• Ferdinand C. Grozema,
• Laurens D. A. Siebbeles and
• Frank Würthner

Beilstein J. Org. Chem. 2010, 6, 1070–1078, doi:10.3762/bjoc.6.122

• chromophores (Scheme 3). To ascertain the involvement of hydrogen bonding in the self-assembly, we examined the effect of a protic solvent, e.g. MeOH, on the self-assembly process by UV-vis spectroscopy. MeOH itself can be involved in H-bonding interaction with the amide groups, and thus expected to interfere

Differences between β-Ala and Gly-Gly in the design of amino acids-based hydrogels

• Andreea Pasc,
• Firmin Obounou Akong,
• Sedat Cosgun and
• Christine Gérardin

Beilstein J. Org. Chem. 2010, 6, 973–977, doi:10.3762/bjoc.6.109

• amphiphiles, we have recently shown that Gly-Gly-His and β-Ala-His-amphiphiles act as efficient hydrogelators [10]. The histidine moiety seems to play a key role in hydrogel formation, developing not only π-π stacking interactions but also by H-bonding; by replacing histidine by phenylalanine no hydrogel

• and FT-IR measurements were performed on β-Ala-His-EO2-C14. The FT-IR measurements were made in order to evaluate the driving forces for the hydrogelation. As expected ATR measurements (Figure 2) show the presence of H-bonding of the amides. The absorptions frequencies in the gel are always lower than

• mechanism. On reducing the temperature to a certain value, amphiphilic molecules start to interact with each other by H-bonding to form micellar networks. The hydrophobicity of the 1D system is proportional to its length. Once the micellar fibre is too long, and thus too hydrophobic to be solubilised by

Pyridinium based amphiphilic hydrogelators as potential antibacterial agents

• Sayanti Brahmachari,
• Sisir Debnath,
• Sounak Dutta and
• Prasanta Kumar Das

Beilstein J. Org. Chem. 2010, 6, 859–868, doi:10.3762/bjoc.6.101

• existence of a non-hydrogen bonded amide group. Hydrogen bond formation is accompanied by a decrease in the bond order and hence the observed shift in the carbonyl stretching frequency to a lower value underlines the participation of intermolecular H-bonding in the gel state [37]. In addition, the N–H

Synthesis and crystallographic analysis of meso-2,3-difluoro-1,4-butanediol and meso-1,4-dibenzyloxy-2,3-difluorobutane

• Bruno Linclau,
• Leo Leung,
• Jean Nonnenmacher and
• Graham Tizzard

Beilstein J. Org. Chem. 2010, 6, No. 62, doi:10.3762/bjoc.6.62

• group does adopt a gauche conformation with its adjacent fluoro substituent where the F–C–C–O dihedral angle is 71.5°. Although strong H-bonding interactions are absent within the crystal, each molecule displays eight short contacts less than the sum of the van der Waals radii to its four nearest

The C–F bond as a conformational tool in organic and biological chemistry

• Luke Hunter

Beilstein J. Org. Chem. 2010, 6, No. 38, doi:10.3762/bjoc.6.38

• an intramolecular hydrogen bond helping to stabilise the gauche conformers of 8 and 9, but the gauche preference is also maintained in systems such as 10 (Figure 1b) which cannot accommodate a hydrogen bond [10], confirming that the charge–dipole interaction is more important than any weak H-bonding

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

A convenient method for preparing rigid-core ionic liquid crystals

• Julien Fouchet,
• Laurent Douce,
• Benoît Heinrich,
• Richard Welter and
• Alain Louati

Beilstein J. Org. Chem. 2009, 5, No. 51, doi:10.3762/bjoc.5.51

• , with δ 10.45 (1a) 9.37 (1b), 9.10 (1c), 9.41 (1d) and 8.98 ppm (1e). This dependency is certainly due to the interactions though H-bonding and the charge localisation on the anion. The UV spectra displays typical charge transfer (π–π* or n–n*) transitions in CH2Cl2 at 240 nm (1a ε = 24000 M−1 cm−1

Quinoline based receptor in fluorometric discrimination of carboxylic acids

• Kumaresh Ghosh,
• Suman Adhikari,
• Asoke P. Chattopadhyay and
• Purnendu Roy Chowdhury

Beilstein J. Org. Chem. 2008, 4, No. 52, doi:10.3762/bjoc.4.52

• into the cavity, also moved significantly downfield upon complexation. Among the three types of CH2 protons (a, b and c; see the structure 1), types a and c moved more downfield (Δδ = 0.07–0.20 ppm) indicating a clear-cut case of H-bonding. This significant downfield shift of the CH2 protons (types a

• and c type protons of the ether chains undergo downfield shift upon complexation with citric acid. This subtle change via H-bonding presumably influences the quinoline groups to be close enough for formation of excimer. This is also evidenced by a change in the chemical shift values of the quinoline

The first organocatalytic carbonyl- ene reaction: isomerisation- free C-C bond formations catalysed by H-bonding thio- ureas

• Matthew L. Clarke,
• Charlotte E. S. Jones and
• Marcia B. France

Beilstein J. Org. Chem. 2007, 3, No. 24, doi:10.1186/1860-5397-3-24

• of highly activated enophiles can be catalysed by H-bonding thio-ureas to give tertiary alcohols in high yields without extensive isomerisation side products. An asymmetric variant of this reaction was realised using a chiral thiourea but was limited by low enantioselectivity (up to 33% e.e.) and low

• interest in hydrogen bond mediated catalysis,[11] we have investigated thioureas as H-bonding additives for organocatalytic carbonyl ene reactions and report these results here. Despite the explosive growth in organocatalytic reactions in recent years, [12][13][14][15][16] this represents, to the best of

• times. Other minor side products were formed from the decomposition of ethyl trifluoropyruvate, but were readily separated from compounds 3 and 4. This decomposition becomes more significant as the reaction is left longer. An investigation into the effect of various H-bonding additives on this reaction

An efficient synthesis of tetramic acid derivatives with extended conjugation from L-Ascorbic Acid

• Biswajit K. Singh,
• Surendra S. Bisht and
• Rama P. Tripathi

Beilstein J. Org. Chem. 2006, 2, No. 24, doi:10.1186/1860-5397-2-24

• . Tetramic acid antibiotics from natural sources. H-bonding in tetronolactonyl dienyl esters. Synthesis of tetronolactonyl aldehydes from L-ascorbic acid Synthesis of tetronolactonyl dienyl esters from etronolactonyl aldehydes Synthesis of 5-hydroxy lactams from dienyl tetronic esters Synthesis of dienyl

The oxanorbornene approach to 3-hydroxy, 3,4-dihydroxy and 3,4,5-trihydroxy derivatives of 2-aminocyclohexanecarboxylic acid

• Ishmael B. Masesane,
• Andrei S. Batsanov,
• Judith A. K. Howard,
• Raju Mondal and
• Patrick G. Steel

Beilstein J. Org. Chem. 2006, 2, No. 9, doi:10.1186/1860-5397-2-9

• . Highly selective epoxidations of cycloalkenyl amides have been described[23] and, consistent with a hypothesis that the mixture of 10 and 11 arise through competing H-bonding directing effects of the carbamate and hydroxyl groups, acetylation of the free hydroxyl group prior to oxidation enhanced the