Synthesis of pyrimido[1,6-a]quinoxalines via intermolecular trapping of thermally generated acyl(quinoxalin-2-yl)ketenes by Schiff bases

• Svetlana O. Kasatkina,
• Ekaterina E. Stepanova,
• Maksim V. Dmitriev,
• Ivan G. Mokrushin and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2018, 14, 1734–1742, doi:10.3762/bjoc.14.147

• reaction (Table 1) was not detected. The most likely way of the formation of quinoxalinone 4a is hydration of the ketene with subsequent decarboxylation (Scheme 2); more careful drying the reaction vials and solvents easily reduced the amount of compound 4a. The formation of pyrido[1,2-a]quinoxaline 5a can

Spectroelectrochemical studies on the effect of cations in the alkaline glycerol oxidation reaction over carbon nanotube-supported Pd nanoparticles

• Dennis Hiltrop,
• Steffen Cychy,
• Karina Elumeeva,
• Wolfgang Schuhmann and
• Martin Muhler

Beilstein J. Org. Chem. 2018, 14, 1428–1435, doi:10.3762/bjoc.14.120

• the cation (2). The formation of the structures (1) or (2) was correlated to the hydration energies (ΔHM) of the cations. Highly charged species with a high ΔHM like Li+ were considered more likely to form structure (2), because the cation–OHads interaction is stronger than for cations with a low ΔHM

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

• small molecules comprise various heterocyclic and/or aromatic hydrocarbon rings with limited rotational freedom and torsion, allowing these drugs to fit into major/minor grooves of DNA by displacing water molecules from the spine of hydration as shown in the Figure 2 [25][26][27]. These molecules bind

Mechanochemistry of nucleosides, nucleotides and related materials

• Olga Eguaogie,
• Joseph S. Vyle,
• Patrick F. Conlon,
• Manuela A. Gîlea and
• Yipei Liang

Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81

• DNA and RNA isolation The lack of free-volume within double-stranded DNA at low hydration levels leads to limited ice formation even under cooling in liquid air [57]. In contrast, cold denaturation of globular proteins at such temperatures is almost ubiquitous [58]. Furthermore, large conformational

Is the tungsten(IV) complex (NEt₄)₂[WO(mnt)₂] a functional analogue of acetylene hydratase?

• Matthias Schreyer and
• Lukas Hintermann

Beilstein J. Org. Chem. 2017, 13, 2332–2339, doi:10.3762/bjoc.13.230

• absence of a satisfactory mechanistic proposal for the hydration reaction, we considered the possibility of a metal–vinylidene type activation mode, as it is well established for ruthenium-based alkyne hydration catalysts with anti-Markovnikov regioselectivity. To validate the hypothesis, the

• regioselectivity of tungsten-catalyzed alkyne hydration of a terminal, higher alkyne had to be determined. However, complex 1 was not a competent catalyst for the hydration of 1-octyne under the conditions tested. Furthermore, we could not observe the earlier reported hydration activity of complex 1 towards

• acetylene. A critical assessment of, and a possible explanation for the earlier reported results are offered. The title question is answered with "no". Keywords: acetylene hydratase; alkynes; catalytic hydration; enzyme models; tungsten complexes; Introduction In 1985, the enzyme acetylene hydratase

Solid-state studies and antioxidant properties of the γ-cyclodextrin·fisetin inclusion compound

• Joana M. Pais,
• Maria João Barroca,
• Maria Paula M. Marques,
• Filipe A. Almeida Paz and
• Susana S. Braga

Beilstein J. Org. Chem. 2017, 13, 2138–2145, doi:10.3762/bjoc.13.212

• conducted on the freeze-dried samples. The elemental analysis data are in agreement with the values calculated for a 1:1 stoichiometry, i.e., the empirical formula C48H80O40·C15H10O6·20H2O. Note also the remarkable increase in the hydration status, from 7 water molecules per host molecule in γ-CD to 20

• and C4 carbons, multiplicity is associated with differences in the conformation about the α(1→4) linkages, while carbons positioned closer to the rims, such as is the case for C6, are more sensitive to ambient changes arising from hydration water molecules and the hydrogen-bonding network [33][34

• . 280 °C, after which the charred residue undergoes a slow thermal oxidation from 330 °C until its complete combustion at 520 °C [38]. The thermal decomposition trace of the physical mixture is quite similar to that of γ-CD, having approximately the same number of hydration water molecules. Remarkably

Remarkable functions of sn-3 hydroxy and phosphocholine groups in 1,2-diacyl-sn-glycerolipids to induce clockwise (+)-helicity around the 1,2-diacyl moiety: Evidence from conformation analysis by ¹H NMR spectroscopy

• Yoshihiro Nishida,
• Mengfei Yuan,
• Kazuo Fukuda,
• Kaito Fujisawa,
• Hirofumi Dohi and
• Hirotaka Uzawa

Beilstein J. Org. Chem. 2017, 13, 1999–2009, doi:10.3762/bjoc.13.196

• hydration occurring around the carbonyl groups in the 1,2-diacyl moiety triggers the dynamics of the molecular alignments in liposomes. Probably, an analogous phenomenon related to the solvation around sn-3 OH was observed. Thus, solvation is thought to play a key role in the dynamic conformation change

Accessing simply-substituted 4-hydroxytetrahydroisoquinolines via Pomeranz–Fritsch–Bobbitt reaction with non-activated and moderately-activated systems

• Marco Mottinelli,
• Mathew P. Leese and
• Barry V. L. Potter

Beilstein J. Org. Chem. 2017, 13, 1871–1878, doi:10.3762/bjoc.13.182

• rearrangement product 13 would then lead to the isolated compound 11 upon hydration, either during the reaction or the work-up. However, the precise mechanism for the formation of 11 has yet to be explored and efforts to unravel it lay outside the scope of this work. The addition of 6 M HCl led to the

Opportunities and challenges for the sustainable production of structurally complex diterpenoids in recombinant microbial systems

• Katarina Kemper,
• Max Hirte,
• Markus Reinbold,
• Monika Fuchs and
• Thomas Brück

Beilstein J. Org. Chem. 2017, 13, 845–854, doi:10.3762/bjoc.13.85

• deprotonation with occasional hydration at the C8 position of the carbocation intermediate which yields hydroxylated diphosphate products [62]. MvCPS1, however, catalyzes a C9–C8 hydride shift preceding hydration resulting in the labdane-type diterpene precursor for the antidiabetic marrubiin [63]. Double

Formose reaction accelerated in aerosol-OT reverse micelles

• Makoto Masaoka,
• Tomohiro Michitaka and
• Akihito Hashidzume

Beilstein J. Org. Chem. 2016, 12, 2663–2667, doi:10.3762/bjoc.12.262

• a layer of water molecules with restricted mobility, because of hydration of the hydrophilic group of the surfactant (i.e., the surfactant head) [22][23]. It is likely that the thickness of the layer of restricted water is approximately several nm [24][25]. The water molecules in the interfacial

• layer are more polar than those in the bulk water phase because of polarization caused by hydration of the surfactant head. Since Rw of AOT reverse micelles is practically proportional to w (Figure S1 in Supporting Information File 1), the fraction of water molecules in the interfacial layer increases

A self-assembled cyclodextrin nanocarrier for photoreactive squaraine

• Ulrike Kauscher and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2016, 12, 2535–2542, doi:10.3762/bjoc.12.248

• solution in a round bottom flask. Hydration and extrusion with a Liposofast extruder and membranes with 100 nm pore size yield bilayer vesicles of an approximate size of 100 nm. CDVs were decorated with AdSq by simple addition of the AdSq to the aqueous dispersion of the CDVs. Interestingly, the

A new paradigm for designing ring construction strategies for green organic synthesis: implications for the discovery of multicomponent reactions to build molecules containing a single ring

• John Andraos

Beilstein J. Org. Chem. 2016, 12, 2420–2442, doi:10.3762/bjoc.12.236

• , catalytic hydration of cyclohexene, or catalytic air oxidation of cyclohexane. However, as an intellectual exercise and proof of principle, we may be able to use the results described for integer partitioning to devise creative syntheses for cyclohexanone which involve actual ring construction via 2

Diastereoselective synthesis of 3,4-dihydro-2H-pyran-4-carboxamides through an unusual regiospecific quasi-hydrolysis of a cyano group

• Mikhail Yu. Ievlev,
• Oleg V. Ershov,
• Mikhail Yu. Belikov,
• Angelina G. Milovidova,
• Viktor A. Tafeenko and
• Oleg E. Nasakin

Beilstein J. Org. Chem. 2016, 12, 2093–2098, doi:10.3762/bjoc.12.198

• presence thereof, but all acids promote only the iminolactone decyclization process without traces of lactone derivative 4 (Table 2). It is also important to note that during the reaction pathway (Scheme 3) a carbonyl-assisted carbonitrile hydration effect (CACHE) was occured. The carbonyl group, through

Solvent-free synthesis of novel para-menthane-3,8-diol ester derivatives from citronellal using a polymer-supported scandium triflate catalyst

• Lubabalo Mafu,
• Ben Zeelie and
• Paul Watts

Beilstein J. Org. Chem. 2016, 12, 2046–2054, doi:10.3762/bjoc.12.193

• further hydrogenated over a metal-supported catalyst to yield the cis and trans isomers of menthol 2 (Scheme 1) [4]. Alternatively the acid-catalysed hydration of citronellal (1) results in the synthesis of the cis and trans isomers of para-menthane-3,8-diol (3, Scheme 2). This chemical derivative is well

From steroids to aqueous supramolecular chemistry: an autobiographical career review

• Bruce C. Gibb

Beilstein J. Org. Chem. 2016, 12, 684–701, doi:10.3762/bjoc.12.69

Interactions of cyclodextrins and their derivatives with toxic organophosphorus compounds

• Sophie Letort,
• Sébastien Balieu,
• William Erb,
• Géraldine Gouhier and
• François Estour

Beilstein J. Org. Chem. 2016, 12, 204–228, doi:10.3762/bjoc.12.23

• guest might weaken the hydration water binding, as revealed in DSC experiments by the lower endothermic fusion peak, specific to a dehydration process. X-ray powder diffraction analysis finally confirmed the complex formation. All these studies proved that organophosphorus pesticides are able to

Thermal and oxidative stability of Atlantic salmon oil (Salmo salar L.) and complexation with β-cyclodextrin

• Daniel I. Hădărugă,
• Mustafa Ünlüsayin,
• Alexandra T. Gruia,
• Cristina Birău (Mitroi),
• Gerlinde Rusu and
• Nicoleta G. Hădărugă

Beilstein J. Org. Chem. 2016, 12, 179–191, doi:10.3762/bjoc.12.20

• from complexes. According to the TG analysis, the water content is 4.1–6.4% lower than for the β-CD. This observation supports the formation of the inclusion compound by partial replacement of the hydration water from the CD cavity by the guest compounds (FA glycerides). Studies on the evaluation of

• support the conclusion of formation of the β-CD/FA glyceride inclusion complex by means of water behavior. Hydration water is easier released from the β-CD/ASO complexes obtained at a 3:1 molar ratio. Both DSC and KFT analyses demonstrate this finding with a lower peak temperature and lower “strongly

Scope and limitations of the dual-gold-catalysed hydrophenoxylation of alkynes

• Adrián Gómez-Suárez,
• Yoshihiro Oonishi,
• Anthony R. Martin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2016, 12, 172–178, doi:10.3762/bjoc.12.19

• as 10% of acetophenone, the corresponding hydration product. Furthermore, the formation of a new gold species, which was characterised as the previously reported σ,π-digold–acetylide species could also be observed. This diaurated species can be formed by reaction of [{Au(IPr)}2(µ-OH)][BF4] with

Polydisperse methyl β-cyclodextrin–epichlorohydrin polymers: variable contact time ¹³C CP-MAS solid-state NMR characterization

• Isabelle Mallard,
• Davy Baudelet,
• Franca Castiglione,
• Monica Ferro,
• Walter Panzeri,
• Enzio Ragg and
• Andrea Mele

Beilstein J. Org. Chem. 2015, 11, 2785–2794, doi:10.3762/bjoc.11.299

• atoms in the molecular frame and whether regions of morphological heterogeneity exist or not. At this stage, it is important to stress two points: i) T1ρ describes the relaxation time of the 1H nuclei, and thus it is sensitive to hydrogen parameters only, including, as an example, the hydration state

Aggregation behaviour of amphiphilic cyclodextrins: the nucleation stage by atomistic molecular dynamics simulations

• Giuseppina Raffaini,
• Antonino Mazzaglia and
• Fabio Ganazzoli

Beilstein J. Org. Chem. 2015, 11, 2459–2473, doi:10.3762/bjoc.11.267

• secondary rim so as to maximize the P-chain hydration. It should also be noted that there is a small cluster of five water molecules trapped into the cavity, and quite isolated from the bulk water, with a pattern rather similar to what found in the native β-CD [46]. Interestingly, also in this case there is

• groups significantly cluster so as to minimize the contact with the environment, whereas the hydrophilic P groups show a marked opening to enhance their hydration. The ellipsoidal distortion of the macrocycle caused by the above mentioned interactions should also be noted. As a result, in water the

• for the tight clustering of the H groups to minimize the hydrated surface and for the wide opening of the P groups to maximize their hydration. In conclusion, even though one could denote this arrangement as a 2 + 1 + 1 aggregate, it is best described as a 3 + 1 aggregate. There is a further

Biocatalysis for the application of CO₂ as a chemical feedstock

• Apostolos Alissandratos and
• Christopher J. Easton

Beilstein J. Org. Chem. 2015, 11, 2370–2387, doi:10.3762/bjoc.11.259

• minimised [25][27]. By balancing thermodynamic feasibililty and a low requirement in NADH and ATP or equivalents, Milo and coworkers [25] were able to computationally predict the most efficient synthetic CO2 fixation pathways, using all known natural enzymes. Aqueous solubility and hydration of CO2 A

• . [117] were able to prove that this FDH utilises CO2, rather than HCO3−, as the active species, through experiments carried out at low temperatures where CO2 hydration is slow. The enzyme from Clostridium carboxidivorans was recombinantly expressed in E. coli and shown to display higher CO2 reducing

Evidencing an inner-sphere mechanism for NHC-Au(I)-catalyzed carbene-transfer reactions from ethyl diazoacetate

• Manuel R. Fructos,
• Juan Urbano,
• M. Mar Díaz-Requejo and
• Pedro J. Pérez

Beilstein J. Org. Chem. 2015, 11, 2254–2260, doi:10.3762/bjoc.11.245

• functionalization; olefin cyclopropanation; Introduction The discovery of the catalytic capabilities of soluble gold(I) species toward the hydration of alkynes by Teles and co-workers [1] is considered as the rising of the golden era for the use of this metal in homogeneous catalysis [2][3]. A number of

Influence of bulky yet flexible N-heterocyclic carbene ligands in gold catalysis

• Alba Collado,
• Scott R. Patrick,
• Danila Gasperini,
• Sebastien Meiries and
• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 1809–1814, doi:10.3762/bjoc.11.196

• selected: alkyne hydration, nitrile hydration, and the synthesis of homoallylic ketones. To place these results into context, [Au(IPr)(NTf2)] (10) [46] was also tested under the same conditions. Alkyne hydration Alkyne hydration is an attractive transformation to generate ketones from alkynes with high

• (10–1000 ppm) [51][52][53][56] have been achieved and the transformation has been successfully performed in aqueous media [54][57]. Due to its relevance and importance, the hydration of phenylacetylene was selected as a model transformation to explore the different activity of complexes 7–9. The

• obtained in all cases (Table 1, entries 5–8). However, the best conversion was observed when complex 10 bearing the IPr ligand was used (Table 1, entry 5). Complexes 7–9 afforded lower conversions, with [Au(IHept)(NTf2)] (8) being the most efficient amongst them (Table 1, entries 6–9). Nitrile hydration

Fates of imine intermediates in radical cyclizations of N-sulfonylindoles and ene-sulfonamides

• Hanmo Zhang,
• E. Ben Hay,
• Stephen J. Geib and
• Dennis P. Curran

Beilstein J. Org. Chem. 2015, 11, 1649–1655, doi:10.3762/bjoc.11.181

• Hanmo Zhang E. Ben Hay Stephen J. Geib Dennis P. Curran Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA 10.3762/bjoc.11.181 Abstract Two new fates of imine intermediates formed on radical cyclizations of ene-sulfonamides have been identified, reduction and hydration

• -dihydropyrroles also presumably form spiro-imines as primary products. However, the lactam carbonyl group facilitates the ring-opening of these cyclic imines by a new pathway of hydration and retro-Claisen-type reaction, providing rearranged 2-(2'-formamidoethyl)oxindoles. Keywords: ene-sulfonamide; imine

• substrates were chosen to provide imines with spirocyclic indoline and indolone substituents. We discovered that these imines are rather reactive, being either reduced or undergoing an unusual hydration and retro-Claisen-type reaction of an amide. Here we report the results of these experiments, which add to

Azobenzene-based inhibitors of human carbonic anhydrase II

• Leander Simon Runtsch,
• David Michael Barber,
• Peter Mayer,
• Michael Groll,
• Dirk Trauner and
• Johannes Broichhagen

Beilstein J. Org. Chem. 2015, 11, 1129–1135, doi:10.3762/bjoc.11.127

• ). Azobenzenes 1a and 1d have been synthesized and tested previously (with a CO2 hydration assay), and the Ki values determined in the previous work are one order of magnitude higher than in our findings (Ki (1a) = 665 nM or 29.7; Ki (1d) = 106 nM or 30.7) towards hCAII [6]. Interestingly, in our studies the

• hCAII. a) hCAII (pdb: 2vva [7]) catalyzes the hydration of carbon dioxide to bicarbonate and a proton (left) as well as the hydrolysis of pNPA to acetate and a colored phenolate (λmax = 400 nm). b) Aryl sulfonamide-containing pharmacophores of hCAII. c) Aryl sulfonamide merged to azobenzenes. Crystal