Efficient synthesis of ethyl 2-(oxazolin-2-yl)alkanoates via ethoxycarbonylketene-induced electrophilic ring expansion of aziridines

• Yelong Lei and
• Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 70–76, doi:10.3762/bjoc.18.6

• solubility to all substrates than toluene, the optimal reaction conditions were selected as: diazo ester 1a (0.36 mmol) and 2a (0.3 mmol) in DCE (1 mL) were heated at 130 °C for 20 min with microwave heating. With the optimal reaction conditions in hand, we evaluated the scopes and generalities of both diazo

Bifunctional thiourea-catalyzed asymmetric [3 + 2] annulation reactions of 2-isothiocyanato-1-indanones with barbiturate-based olefins

• Jiang-Song Zhai and
• Da-Ming Du

Beilstein J. Org. Chem. 2022, 18, 25–36, doi:10.3762/bjoc.18.3

• solubility of this substrate. The absolute configuration of the chiral product 3ae was unambiguously identified on the basis of single-crystal X-ray diffraction analysis as (2S,3'S) (Figure 4) [33]. The configurations of the other products were assigned by analogy to 3ae. In order to further prove the

Stepwise PEG synthesis featuring deprotection and coupling in one pot

• Logan Mikesell,
• Dhananjani N. A. M. Eriyagama,
• Yipeng Yin,
• Bao-Yuan Lu and
• Shiyue Fang

Beilstein J. Org. Chem. 2021, 17, 2976–2982, doi:10.3762/bjoc.17.207

• we made will behave similarly. In addition, PEGs are soluble in solvents such as water, toluene, DCM and many other solvents but not soluble in diethyl ether and hexanes. This solubility pattern is very different from most other organic compounds including the side products of the PEG elongation

A two-phase bromination process using tetraalkylammonium hydroxide for the practical synthesis of α-bromolactones from lactones

• Yuki Yamamoto,
• Akihiro Tabuchi,
• Kazumi Hosono,
• Takanori Ochi,
• Kento Yamazaki,
• Shintaro Kodama,
• Akihiro Nomoto and
• Akiya Ogawa

Beilstein J. Org. Chem. 2021, 17, 2906–2914, doi:10.3762/bjoc.17.198

• ). Intramolecular cyclization of the salt forms 3a, which is extracted into the organic layer due to its low solubility in water. Because n-Bu4N+OH− is less-soluble in organic solvents than water, 3a is phase-separable from the base. To our delight, 2a was smoothly converted into 3a in 74% yield in this two-phase

• system, with the reaction time successfully reduced to 1 h (Table 2, entries 1–5). The use of a co-solvent to increase the solubility of 2a was investigated in detail; DMSO was found to be the most effective solvent, with 3a produced in 82% yield (Table 2, entries 5–12). We next optimized the base used

Synthesis of a novel aminobenzene-containing hemicucurbituril and its fluorescence spectral properties with ions

• Qingkai Zeng,
• Qiumeng Long,
• Jihong Lu,
• Li Wang,
• Yuting You,
• Xiaoting Yuan,
• Qianjun Zhang,
• Qingmei Ge,
• Hang Cong and
• Mao Liu

Beilstein J. Org. Chem. 2021, 17, 2840–2847, doi:10.3762/bjoc.17.195

• HQ[n]s with that of Q[n]s, Buschmann [26] observed that HQ[6] 2 (Scheme 1) formed complexes only with Ni2+, Co2+, and UO22+ with extremely low affinity, which may be caused by the poor solubility of HQ[6] 2 in aqueous solution and its universal “alternate” conformation. Most modified

• ions at submicromolar concentrations always by means of NMR spectroscopy [33]. Nevertheless, sensing by UV–vis or fluorescence spectra was hard to realize, for there is no chromophore in the frameworks. While hemicucurbit[n]urils with improvement in solubility, they still remain poor in derivatization

• % yield and 30.0% yield based on starting compounds 5 and 6, respectively (Scheme 2). With the trimers 7 and 8 in hand, the reaction conditions for the [3 + 3] macrocyclic condensation were examined. Due to the low solubility of compound 7, the subsequent reactions were conducted in DMF. With two

Host–guest interaction and properties of cucurbit[8]uril with chloramphenicol

• Lin Zhang,
• Jun Zheng,
• Guangyan Luo,
• Xiaoyue Li,
• Yunqian Zhang,
• Zhu Tao and
• Qianjun Zhang

Beilstein J. Org. Chem. 2021, 17, 2832–2839, doi:10.3762/bjoc.17.194

• in water and has a bitter taste. Upon forming an inclusion complex with cyclodextrin, the solubility and bitter taste of CPE can be improved [4][5]. Ramesh Gannimani et al. [6] reported that the inclusion complex of cyclodextrin and CPE loaded silver nanoparticles possessed stronger antibacterial

• cucurbit[n]urils can be used as non-toxic and safe drug carriers [29][30][31], among which cucurbit[8]uril (Q[8]) [32] has a large cavity. Q[8] interacts with a variety of small drug molecules such as chrysin, oroxin A and B, baicalein, etc., which can enhance the solubility, stability, antioxidant and

• , indicating the formation of a 1:1 host–guest inclusion complex. Due to the poor solubility of Q[8], an acid solution was selected as the medium to grow a crystal of the CPE@Q[8] host–guest inclusion complex. When the interaction between CPE and Q[8] was investigated using 1H NMR spectroscopy, a deuterated

Cryogels: recent applications in 3D-bioprinting, injectable cryogels, drug delivery, and wound healing

• Luke O. Jones,
• Leah Williams,
• Tasmin Boam,
• Martin Kalmet,
• Chidubem Oguike and
• Fiona L. Hatton

Beilstein J. Org. Chem. 2021, 17, 2553–2569, doi:10.3762/bjoc.17.171

• properties and/or morphology. Often it can be characterised in terms of swelling, as the solubility of a polymer within a solvent, or solvation state, changes with temperature in thermally responsive cryogels. This leads to variation in cryogel volume, as at differing temperatures the nature of intra- and

• intermolecular hydrogen bonding changes, leading to variations on how hydrated the cryogel is, triggering a volume phase transition [34][35]. Changes in solubility can be described by the upper critical solution temperature (UCST) and lower critical solution temperatures (LCST). The UCST is the temperature at

A visible-light-induced, metal-free bis-arylation of 2,5-dichlorobenzoquinone

• Pieterjan Winant and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 2315–2320, doi:10.3762/bjoc.17.149

• options for further functionalization. When 4-nitroaniline (4e) was used, the monoarylated product precipitated from the reaction mixture. Due to the very limited solubility of this intermediate, the latter was unable to react further. Changing the solvent to DMSO to try to tackle the solubility issue did

Base-free enantioselective S_N2 alkylation of 2-oxindoles via bifunctional phase-transfer catalysis

• Mili Litvajova,
• Emiliano Sorrentino,
• Brendan Twamley and
• Stephen J. Connon

Beilstein J. Org. Chem. 2021, 17, 2287–2294, doi:10.3762/bjoc.17.146

• conditions, the chloro derivative 9b proved to be the most efficient catalyst – mediating the formation of product 10Aa in 62% ee after full conversion (Table 1, entries 12–15). Attention then turned to the 2-oxindole structure. Due to solubility issues chlorobenzene was chosen as the preferred solvent

(Phenylamino)pyrimidine-1,2,3-triazole derivatives as analogs of imatinib: searching for novel compounds against chronic myeloid leukemia

• Luiz Claudio Ferreira Pimentel,
• Lucas Villas Boas Hoelz,
• Henayle Fernandes Canzian,
• Frederico Silva Castelo Branco,
• Andressa Paula de Oliveira,
• Vinicius Rangel Campos,
• Floriano Paes Silva Júnior,
• Rafael Ferreira Dantas,
• Jackson Antônio Lamounier Camargos Resende,
• Anna Claudia Cunha,
• Nubia Boechat and
• Mônica Macedo Bastos

Beilstein J. Org. Chem. 2021, 17, 2260–2269, doi:10.3762/bjoc.17.144

• original work that led to compound 3, and, additionally, they are able to act as acceptors and donors in hydrogen bonds and thus were expected to increase the aqueous solubility of the compounds. Additionally, Kalesh and co-workers demonstrated good results with derivative 4 which contains the amide group

Chemical syntheses and salient features of azulene-containing homo- and copolymers

• Vijayendra S. Shetti

Beilstein J. Org. Chem. 2021, 17, 2164–2185, doi:10.3762/bjoc.17.139

• by using [Pd(allyl)Cl]2 and JackiePhos as a ligand to obtain the polymer 30 in 52% yield. The deprotection of the N-Boc functionality led to the formation of poly[2,6-aminoazulene] 31 in excellent yields (Scheme 7C). The N-Boc-protected polymer 30 possessed good solubility in organic solvents and its

• , and 56 displayed good solubility in most of the commonly used organic solvents and GPC analysis revealed their number-average molecular weight (Mn) to be in the range of 25800 to 48600 Da with polydispersity in the range 1.29–1.9. They also exhibited excellent thermal stability as indicated by their

• )azulene (114) was required, and its synthesis was achieved from 2-bromofluorene (110) by following the protocol presented in Scheme 19B. The reaction of 114 with fluorene borates 102 and 104 under Suzuki conditions yielded polymers 115 and 116, respectively (Scheme 19C). The solubility of all polymers was

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

• their physicochemical properties (e.g., solubility, viscosity) and can respond to stimuli in several ways by altering light transmitting abilities, shape, color, conductivity, as well as wettability [27][28]. Therefore, such functional polymers have a huge potential in numerous areas of application

• free polymer chains in solution is only conditionally applicable to constrained polymer topologies. The most commonly used stimulus to induce responsive behavior is the temperature [2][43][44][45]. The physicochemical basis for this is a temperature-dependent solubility of a polymer in one or a mixture

• of solvents. In solution, stimuli responsive polymers undergo a conformational, so-called coil-to-globule, transition. Depending on whether the solubility increases below (LCST for lower critical solution temperature [46][47][48][49]) or above (UCST for upper critical solution temperature [50][51][52

Progress and challenges in the synthesis of sequence controlled polysaccharides

• Giulio Fittolani,
• Theodore Tyrikos-Ergas,
• Denisa Vargová,
• Manishkumar A. Chaube and
• Martina Delbianco

Beilstein J. Org. Chem. 2021, 17, 1981–2025, doi:10.3762/bjoc.17.129

• better understanding of cellulose’s properties are hindered by its poor solubility in most solvents. Relatively short oligomers with DPs of 6–10 tend to aggregate and precipitate out of solution [54], making isolation of pure samples troublesome. Much effort has been put to tune the synthetic conditions

• ), including the 6-deoxy [85], 13C-labelled [24], ʟ-Glc [86], and ethyl/methyl analogues [87][88][89]. Depending on the methyl/ethyl content, it was possible to tune the solubility of the polymer in water. 6-O-Methyl- and 6-O-ethyl-celluloses were poorly soluble in water, in contrast to heterogeneous polymers

• , fluorine, and carboxymethyl groups, prevented the formation of insoluble aggregates by disrupting hydrogen-bond networks. Dramatic differences in the conformation (e.g., radius of gyration and glycosidic bond conformation) and aggregation behaviour (i.e., crystallinity and solubility) were observed for

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

• solubility of Cs2CO3 in toluene and 1,4-dioxane [24]. Using K2CO3 in MeCN, Longworth et al. have obtained 10 with a similar degree of N-1 regioselectivity (ratio N-1:N-2 = 2.8:1) [26]. However, altering solvent polarity when employing 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a base (Table 1, entries 15–17

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

• room temperature within 0.1 h for a successful reaction. The salt 5-4v was so powerful that it fluorinated an equimolar amount of benzene in dichloromethane in 2 h at 40 °C. In general, triflate salts were more effective than BF4 salts because of the higher solubility of the triflate salts in a

• these reagents exhibited a low reactivity due to their low solubility in organic solvents [32]. Their fluorinating power increased in the order of 18-2a < 2b ≈ 2c ≈ 2d ≈ 2e < 2f < 2g < 2h, consistent with the order of the pKa values of the pyridines (Scheme 39). The least powerful 18-2a was suitable for

Sustainable manganese catalysis for late-stage C–H functionalization of bioactive structural motifs

• Jongwoo Son

Beilstein J. Org. Chem. 2021, 17, 1733–1751, doi:10.3762/bjoc.17.122

• electron-rich benzylic position, rationalizing the involvement of electrophilic metallonitrene intermediate 18A. Manganese-catalyzed late-stage C–H methylation The incorporation of methyl groups has the potential to manipulate absorption, distribution, metabolism, and excretion (ADME), solubility, and

Cerium-photocatalyzed aerobic oxidation of benzylic alcohols to aldehydes and ketones

• Girish Suresh Yedase,
• Sumit Kumar,
• Jessica Stahl,
• Burkhard König and
• Veera Reddy Yatham

Beilstein J. Org. Chem. 2021, 17, 1727–1732, doi:10.3762/bjoc.17.121

• transfer (LMCT) process, which reduces the CeIV species to CeIII, similarly as reported by Zuo and co-workers [57]. We chose (n-Bu4N)2CeIVCl6 as the CeIV source to ensure a sufficient solubility in organic solvents and to facilitate the detection of the species. The CeIV(OBn)Cln complex was prepared by

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

• potential from 1.400 V (TPP) to 1.050 V (TMTPP) [35]. Furthermore, the share of phosphine oxide is dependent on the oxygen solubility in the solvent, as indicated by the experiments in chloroform and 1-hexanol exhibiting the higher oxygen solubility [36]. To obtain further insight, the SOMO energies of the

Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

• Nikita Brodyagin,
• Martins Katkevics,
• Venubabu Kotikam,
• Christopher A. Ryan and
• Eriks Rozners

Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116

• therapeutics. While many modifications have improved on PNA’s binding affinity and specificity, solubility and other biophysical properties, the original PNA is still most frequently used in diagnostic and other in vitro applications. Development of therapeutics and other in vivo applications of PNA has

• vulnerabilities. Limited water solubility, especially for purine rich sequences, was noted in early studies. To improve water solubility and decrease aggregation, typical PNA designs place a lysine at the C-terminus (Figure 1) introducing a second positive charge in addition to the charge at the N-terminus of PNA

• [1]. Even with the additional lysine, the solubility of PNA decreases as the polymer length increases. PNA solubility in the HEPES buffer at pH 7.3 and 37 °C is estimated to be in the 0.1–0.5 mM range [12][13]. The hydrophobic nature and lack of electrostatic repulsion of the PNA backbone favors

Recent advances in the application of isoindigo derivatives in materials chemistry

• Andrei V. Bogdanov and
• Vladimir F. Mironov

Beilstein J. Org. Chem. 2021, 17, 1533–1564, doi:10.3762/bjoc.17.111

• properties [6][7][8][9][10][11][12]. The main photophysical characteristics that determine the effectiveness of OSCs are open circuit voltage (VOC), short-circuit current (JSC) and fill factor (FF). In addition, the solubility of isoindigo derivatives in organic solvents is very important since this affects

• efficiency values of 7.3%. The problem of the low solubility of such polymers was partially solved by inserting an alkylene spacer between two thiophene fragments in one of the monomer units [44]. Efficiency (3.0–3.7%) and viscosity characteristics provide good prerequisites for the use of this type of

• possibility of varying optoelectronic properties, and good solubility in a wide range of solvents [59][60][61]. In this regard, the most studied and promising are π-conjugated polymer structures based on sulfur, oxygen, nitrogen, and selenium heterocyclic compounds [62][63]. One of the systems for creating

Substituted nitrogen-bridged diazocines

• Pascal Lentes,
• Jeremy Rudtke,
• Thomas Griebenow and
• Rainer Herges

Beilstein J. Org. Chem. 2021, 17, 1503–1508, doi:10.3762/bjoc.17.107

• . Moreover, the photoconversion yield for the E→Z isomerization is quantitative (within the detection limit of UV and NMR spectroscopy). A high efficiency in switching the biological activity off is important to avoid side effects of residual concentrations of the active form [13]. Water solubility and high

Co-crystallization of an organic solid and a tetraaryladamantane at room temperature

• Fabian Rami,
• Jan Nowak,
• Felix Krupp,
• Wolfgang Frey and
• Clemens Richert

Beilstein J. Org. Chem. 2021, 17, 1476–1480, doi:10.3762/bjoc.17.103

• elevated temperature using the thermal crystallization approach [17]. However, achieving a high end temperature of the temperature gradient met with technical difficulties and the approach was further complicated by the high solubility of the TAAs tested in the phenol melts. This prompted us to test a more

Design, synthesis and photophysical properties of novel star-shaped truxene-based heterocycles utilizing ring-closing metathesis, Clauson–Kaas, Van Leusen and Ullmann-type reactions as key tools

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2021, 17, 1374–1384, doi:10.3762/bjoc.17.96

• interdisciplinary interest from both fundamental as well as applied viewpoint on account of their wonderful optoelectronic properties. The scientific interest in two-dimensional star-shaped PAHs particularly in truxene architectures arises because of their high thermal stability, exceptional solubility and ease

• , superior solubility, improve morphological, optical, electrical and film-forming properties because of the involvement of extra dimensionality. Amongst them, the heptacyclic truxene scaffold possessing three overlapping fluorene units and its congeners are of archetypal interest due to their potential

• exploding day-by-day, thanks to its easy construction, and solubility in common organic solvents in addition to remarkable structural modifications of the truxene framework. Interestingly, the area of truxene is now fully matured, scientist’s imagination is the only limit for designing novel truxene-based

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

• ), column robustness/ease of recyclability and the facile nature of reaction condition and substrate screening. To increase the greenness and reduce the consumption of the catalyst, Yamamoto and Nakashima have recently developed a proline tetrazole 51 packed-bed reactor system, exploiting the low solubility

• system without the need for supports, hence only modifying the solubility of the catalyst. However, in the above-described reactors the main drawbacks presented were the high pressure drop along the column and the poor handling of solid particles. This resulted in a reduced reliability especially during

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• in its increased solubility. The impact of the addition of 30 mol % NH4PF6 caused that the product yield was almost doubled even when the temperature was 20 °C lower (Table 19) [48], while there was only a minimal to no effect on the enantioselectivity (Table 19). Scale-up to a gram-scale was