Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• as photocatalyst (Scheme 32) [67]. Instead of using dioxygen as sacrificial oxidant and basic additives for proton scavenging, they installed a second catalytic cycle for proton reduction deliberating dihydrogen as byproduct. The reaction is proposed to proceed via a reductive quenching of the

• production could only be achieved by careful selection and adjustment of the type and amount of basic additives. The scope of this method includes electron-rich and electron-deficient 2-aryl-substituted benzothiophenes. However, strongly electron-donating methoxy or electron-withdrawing trifluoromethyl

• later, Lei and co-workers reported a photocatalyzed oxidant-free method for the preparation of allyl sulfones from sulfinic acids and α-methylsytrenes, applying Eosin Y as organic photocatalyst and avoiding any sacrificial additives or oxidants (Scheme 45) [82]. They successfully applied the proton

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• positions of the heterocycles; however, it was noticed that the regioselectivity can be tuned simply by solvent choice. Langlois and others employed catalytic metal salts for reaction initiation but Baran’s group demonstrated that metal additives were not required for a productive reaction, only trace

Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and β-ketoamides

• Irwan Iskandar Roslan,
• Kian-Hong Ng,
• Gaik-Khuan Chuah and
• Stephan Jaenicke

Beilstein J. Org. Chem. 2017, 13, 2739–2750, doi:10.3762/bjoc.13.270

• silylation [72]. In these reactions, the single electron transfer (SET) is initiated by KOt-Bu/DMF [63][67][69][71] or KOt-Bu in combination with additives such as bidentate diamine ligands [61][62][63][64][65], 18-crown-6 [70] or azobisisobutyronitrile (AIBN) [62][66]. Herein, we report the synthesis of

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

• GRAS status (list of food additives that are ‘generally recognized as safe’) [9]. The present work describes the preparation of a water-soluble, solid inclusion compound of fisetin with γ-CD (see Scheme 1 for structure and atom labeling). The formation of the γ-CD·fisetin inclusion compound as a solid

Preactivation-based chemoselective glycosylations: A powerful strategy for oligosaccharide assembly

• Weizhun Yang,
• Bo Yang,
• Sherif Ramadan and
• Xuefei Huang

Beilstein J. Org. Chem. 2017, 13, 2094–2114, doi:10.3762/bjoc.13.207

• are intrinsically sensitive to factors including protective groups on the glycan ring, reaction solvent, and additives present. As a result, further experimentation and analysis are needed to enable robust syntheses and achieve automation with comparable efficiencies of automated peptide and nucleic

Main group mechanochemistry

• Agota A. Gečiauskaitė and
• Felipe García

Beilstein J. Org. Chem. 2017, 13, 2068–2077, doi:10.3762/bjoc.13.204

• process is via the use of small amounts of liquid and/or solid additives, termed ion- and liquid-assisted (ILAG) or liquid-assisted grinding (LAG), respectively [34][35]. These techniques, in contrast to “dry” milling, often offer advantages such as shorter reaction times and/or greater product

Mechanically induced oxidation of alcohols to aldehydes and ketones in ambient air: Revisiting TEMPO-assisted oxidations

• Andrea Porcheddu,
• Evelina Colacino,
• Giancarlo Cravotto,
• Francesco Delogu and
• Lidia De Luca

Beilstein J. Org. Chem. 2017, 13, 2049–2055, doi:10.3762/bjoc.13.202

• the bpy/CuI/NMI catalyst system with Fe(NO3)3·9H2O, a cheaper, ligand-free co-oxidant (Scheme 1) [29][30]. This made the oxidative process more appealing for pharmaceutical applications, and specifically beneficial in the preparation of fragrances and food additives [31]. Despite the advances, the

1,3-Dibromo-5,5-dimethylhydantoin as promoter for glycosylations using thioglycosides

• Fei-Fei Xu,
• Claney L. Pereira and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2017, 13, 1994–1998, doi:10.3762/bjoc.13.195

• thioglycosides. Results and Discussion Initially, the capability of DBDMH to activate thioglycoside 1 [32] in order to glycosylate the primary hydroxy group present in D-glucose acceptor 2 [33] was explored without any additives (Table 1, entry 1). This initial experiment furnished disaccharide 3, albeit in

One-pot multistep mechanochemical synthesis of fluorinated pyrazolones

• Joseph L. Howard,
• William Nicholson,
• Yerbol Sagatov and
• Duncan L. Browne

Beilstein J. Org. Chem. 2017, 13, 1950–1956, doi:10.3762/bjoc.13.189

• considered for use in a multistep format [14][15][16]. Having recently begun our research programme in the area of mechanochemistry, we were particularly intrigued by the compatibility of differing chemical forms and additives across a two-step, one-grinding jar solventless process. To investigate this we

• optimum reaction time for the isolated step rather than two-step, i.e., the pyrazolone material was isolated from step one and purified before subjecting to this second reaction optimisation. With no additives, the fluorination was complete after 2 hours (Table 2, entry 4), notably an extra hour returned

Pd(OAc)₂/Ph₃P-catalyzed dimerization of isoprene and synthesis of monoterpenic heterocycles

• Dominik Kellner,
• Maximilian Weger,
• Andrea Gini and
• Olga García Mancheño

Beilstein J. Org. Chem. 2017, 13, 1807–1815, doi:10.3762/bjoc.13.175

• that are used as alkyd coatings and perfume additives [39][40]. In addition, further functionalization reactions of the isoprene dimers can be carried out. In this work, we envisioned the synthesis of various heterocycles by (hetero)Diels–Alder and [4 + 1]-cycloadditions with nitrenes with the obtained

Selective enzymatic esterification of lignin model compounds in the ball mill

• Ulla Weißbach,
• Saumya Dabral,
• Laure Konnert,
• Carsten Bolm and
• José G. Hernández

Beilstein J. Org. Chem. 2017, 13, 1788–1795, doi:10.3762/bjoc.13.173

• milling, reaction time and additives was also investigated (Table S1 in Supporting Information File 1). In addition to this, the catalytic activity of a number of other lipases was studied (Table 1). Amongst the commercially available lipases, CALA (lipase A from Candida antarctica, immobilized on

• (1.0 equiv) and phenol derivatives (guaiacol, 3-methoxyphenol, etc.) were carried out. In most cases, the presence of the additives had no negative effect on the performance of CALB (for details see Table S2 in Supporting Information File 1). Only the presence of 2,2’-biphenol seemed to have slowed

• , milling frequency, presence of additives and different acyl donors were studied in detail. Amongst the various biocatalysts tested, the lipase CALB proved superior in terms of catalytic activity and stability in the ball mill. The high catalytic activity of the enzyme facilitated the monoacetylation of β

Mechanochemical enzymatic resolution of N-benzylated-β³-amino esters

• Mario Pérez-Venegas,
• Gloria Reyes-Rangel,
• Adrián Neri,
• Jaime Escalante and
• Eusebio Juaristi

Beilstein J. Org. Chem. 2017, 13, 1728–1734, doi:10.3762/bjoc.13.167

• %, and presented high ee (95%, E > 200). These data represent an improvement both in ee and yield compared with the data recorded in solution [52]. Motivated by this result, we investigated the effect of other LAG additives in the reaction (see Supporting Information File 1, Table S1, entries 4–10). When

• 2M2B was replaced with other LAG additives a lower yield was observed (Table 1, entries 4–6). Nevertheless, the enantioselectivity of the process is maintained (95% ee), except when hexane was used (Table 1, entry 7), where a higher yield was observed (60%) although with a lower enantiomeric excess (86

Phenylsilane as an effective desulfinylation reagent

• Wanda H. Midura,
• Aneta Rzewnicka and
• Jerzy A. Krysiak

Beilstein J. Org. Chem. 2017, 13, 1513–1517, doi:10.3762/bjoc.13.150

• reported. Apart from traditional hydride reducing agents like lithium aluminum hydride and sodium borohydride [1][2], different modifications were applied, using transition metal salts as catalysts or additives to change or enhance the properties of these reagents [3][4][5][6][7][8]. Hydrogenation is

Photocatalyzed synthesis of isochromanones and isobenzofuranones under batch and flow conditions

• Manuel Anselmo,
• Lisa Moni,
• Hossny Ismail,
• Davide Comoretto,
• Renata Riva and
• Andrea Basso

Beilstein J. Org. Chem. 2017, 13, 1456–1462, doi:10.3762/bjoc.13.143

• multicomponent adducts. It was rather curious instead to find out that many solvents or additives would attack the radical/cationic intermediate while reactants rationally and appositely selected would not. Some products unexpectedly obtained during various attempts are shown in Figure 1. In some cases also 1,2

Switchable highly regioselective synthesis of 3,4-dihydroquinoxalin-2(1H)ones from o-phenylenediamines and aroylpyruvates

• Juraj Dobiaš,
• Marek Ondruš,
• Gabriela Addová and
• Andrej Boháč

Beilstein J. Org. Chem. 2017, 13, 1350–1360, doi:10.3762/bjoc.13.132

• , rt, 3 days), differing only by the additives p-TsOH or HOBt/DIC (hydroxybenzotriazole/N,N’-diisopropylcarbodiimide). Both selected methods are simple, general and highly regioselective (72–97%). A mechanism for the regioselectivity was also proposed and discussed. This study can be used as a guide

• -donating groups and halogens (EDG or HG) or (b) with electron-withdrawing (EWG) groups (Table 1, Scheme 6). Using the general procedure A without any additives, diamine 11 was always almost quantitatively consumed (90–100%), and for both clusters of substituents on 11, the main regioisomer of 3,4

• or the contrary regioselectivity of activated species 12c,d (prepared in situ from appropriate 12 by DMAP – 12c or HOBt/DIC additives – 12d) (Scheme 6). Conclusion Simple reaction conditions were discovered for predictable and switchable highly regioselective synthesis of 3,4-dihydroquinoxaline-2(1H

Construction of highly enantioenriched spirocyclopentaneoxindoles containing four consecutive stereocenters via thiourea-catalyzed asymmetric Michael–Henry cascade reactions

• Yonglei Du,
• Jian Li,
• Kerong Chen,
• Chenglin Wu,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2017, 13, 1342–1349, doi:10.3762/bjoc.13.131

• chloroform were further screened. The results suggested that changing the solvent had an adverse effect on the ee value, and CH2Cl2 remained the best choice for this transformation (Table 1, entries 4, 7–11). Subsequently, we investigated some additives, for example, p-MeC6H4SO3H, trimethylsilyl chloride

• (TMSCl) and trifluoroacetic acid (TFA) for this catalytic system to increase the ee value of the target product; however, the use of the additives proved ineffective (Table 1, entries 15–17). With the optimized reaction conditions established, we next investigated the substrate scope of 3-substituted

One-pot synthesis of block-copolyrotaxanes through controlled rotaxa-polymerization

• Jessica Hilschmann,
• Gerhard Wenz and
• Gergely Kali

Beilstein J. Org. Chem. 2017, 13, 1310–1315, doi:10.3762/bjoc.13.127

• other polymerization techniques, such as atom transfer radical polymerization, because of the lack of toxic metal additives, and because of good control exerted in aqueous solution. The water-soluble bifunctional CTA S,S′-bis(α,α′-dimethyl-α′′-acetic acid)trithiocarbonate (DMATC) was selected because it

Aggregation behaviour of a single-chain, phenylene-modified bolalipid and its miscibility with classical phospholipids

• Simon Drescher,
• Vasil M. Garamus,
• Christopher J. Garvey,
• Annette Meister and
• Alfred Blume

Beilstein J. Org. Chem. 2017, 13, 995–1007, doi:10.3762/bjoc.13.99

• objects, whose numerical solution is searched for. In present analysis, the maximal thickness of disks is needed. To get a sufficient fit of experimental data and a stable shape of pT(r) function, a maximal thickness of 55 Å has been applied. The comparison with pure DPPC bilayers (without additives

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

• largest and most structurally diverse group of natural products. They are ubiquitous in bacteria, plants, animals and fungi, conducting several biological functions such as cell wall components or defense mechanisms. Industrial applications entail among others pharmaceuticals, food additives, vitamins

• , fragrances, fuels and fuel additives. Central building blocks of all terpenes are the isoprenoid compounds isopentenyl diphosphate and dimethylallyl diphosphate. Bacteria like Escherichia coli harbor a native metabolic pathway for these isoprenoids that is quite amenable for genetic engineering. Together

• ), artemisinin [2] (antimalarial agent) and α-pinene [3] (antibiotic, anti-inflammatory). Apart from bioactive compounds with applications as drugs/pharmaceuticals [4] or in the nutrition or agricultural sector, isoprenoids of minor structural complexity are used as bulk chemicals or fuel additives [5][6]. To

DMAP-assisted sulfonylation as an efficient step for the methylation of primary amine motifs on solid support

• Johnny N. Naoum,
• Koushik Chandra,
• Dorit Shemesh,
• R. Benny Gerber,
• Chaim Gilon and
• Mattan Hurevich

Beilstein J. Org. Chem. 2017, 13, 806–816, doi:10.3762/bjoc.13.81

• , entry 7). To further evaluate the effect of base on the conversion and purity, another study was performed with motif 4 as a model using DBU, DMAP, pyridine, and collidine as additives. HPLC analysis showed that the additive used indeed has an impact on the conversion of 4 to 4a and on the crude purity

• . DBU proved to be the poorest additive as no conversion was detected (Figure 3, iii). The analysis indicated that using collidine and pyridine as additives resulted in low conversion and in the accumulation of byproducts (Figure 3, iv and v). When DMAP was used, a conversion of 98% from motif 4 to

• motif 4a was recorded with almost no byproducts (Figure 3, vi). The replacement of collidine with the other additives provided us with important information. DBU, which is considered a more reactive base than the other reagents, proved the less effective additive. This suggested that the reaction is not

Continuous-flow processes for the catalytic partial hydrogenation reaction of alkynes

• Carmen Moreno-Marrodan,
• Francesca Liguori and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2017, 13, 734–754, doi:10.3762/bjoc.13.73

• liquid phase is a reaction of high relevance to the manufacture of a multitude of fine chemicals [1] including pharmaceutical building blocks, agrochemicals, food additives, flavours and fragrances [2][3]. It is also crucial in the bulk polymer industry to achieve the complete elimination of alkynes and

• observed in the fine-chemicals sector [22][23], as a consequence of the additives and manipulations required to achieve satisfactory selectivity. Indeed, the implementation of continuous-flow practices in the pharmaceutical industry is considered one of the most strategic fields of innovation toward

• terms of productivity per unit active metal, volume or time, absence of additives or catalyst lifetime [26][27]. In the present paper we shortly review the heterogeneous catalytic systems engineered for the partial hydrogenation reaction of substituted and unsubstituted alkynes under continuous flow and

Fluorescent carbon dots from mono- and polysaccharides: synthesis, properties and applications

• Stephen Hill and
• M. Carmen Galan

Beilstein J. Org. Chem. 2017, 13, 675–693, doi:10.3762/bjoc.13.67

• morphologies. It should be stated that no two CD preparations lead to the same type of nanoparticle, as any changes to the ratio and composition of starting materials, additives, solvent, temperature, type of vessel, etc., does have an effect on the final molecular composition and architecture of the CD

• -tuning the reaction conditions, combined with the use of additives, can lead to modifications in the emissive properties of the nanoparticles [20]. The team was able to show that the use of sulfuric acid with a carbohydrate, although the exact carbohydrate used is not disclosed in the article, generally

Synthesis of new pyrrolidine-based organocatalysts and study of their use in the asymmetric Michael addition of aldehydes to nitroolefins

• Alejandro Castán,
• Ramón Badorrey,
• José A. Gálvez and
• María D. Díaz-de-Villegas

Beilstein J. Org. Chem. 2017, 13, 612–619, doi:10.3762/bjoc.13.59

• is worth mentioning that on reducing the catalyst loading to 5 mol % the reactivity remained good and the diastereoselectivity and enantioselectivity were only slightly affected. It has been reported that additives present in the reaction medium can lead to improved results without changing other

• hand, the presence of thiourea additives could activate nitroalkenes when used as substrates by double hydrogen bonding, which lead to improved reactivities [24]. Based on these findings, we decided to explore the effect of a Brønsted acid or an achiral thiourea as additive on the reaction between

• trans-β-nitrostyrene and 3-phenylpropionaldehyde promoted by OC4 (Table 4). When thioureas were used as additives the reaction was performed in toluene in order to improve the solubility. The addition of benzoic or acetic acid increased the reactivity and anti-enantioselectivity but it was detrimental

Transition-metal-catalyzed synthesis of phenols and aryl thiols

• Yajun Liu,
• Shasha Liu and
• Yan Xiao

Beilstein J. Org. Chem. 2017, 13, 589–611, doi:10.3762/bjoc.13.58

• stoichiometric amount of Cu(OAc)2 in the presence of Ag2CO3 and TBAI as additives in DMF at 100 °C (Scheme 26). Notably, their protocol was so efficient that the reactions could accomplish within 1 hour. The substrate scope showed benzamides bearing both electron-donating groups and electron-withdrawing groups

• used 10 mol % of Pd(OAc)2 as catalyst, and the reaction was carried out under the atmosphere of molecular oxygen in the presence of KOAc and 1,4-benzoquinone (BQ) as additives (Scheme 40). The mechanism investigation indicated that molecular oxygen was involved in the product forming step rather than

Poly(ethylene glycol)s as grinding additives in the mechanochemical preparation of highly functionalized 3,5-disubstituted hydantoins

• Andrea Mascitti,
• Massimiliano Lupacchini,
• Ruben Guerra,
• Ilya Taydakov,
• Lucia Tonucci,
• Nicola d’Alessandro,
• Frederic Lamaty,
• Jean Martinez and
• Evelina Colacino

Beilstein J. Org. Chem. 2017, 13, 19–25, doi:10.3762/bjoc.13.3

• -isobutylhydantoin (2a) (R1 = CH2CH(CH3)2 and R2 = CH2CH3, Scheme 1) [9]. The reaction was screened in the presence of various PEG additives (Table 1), by adding variable amounts of PEGs, with different molecular weights (600 < Mw < 5000 Dalton) or chain end groups (dihydroxy, mono- or dimethyl ether substituents

• actually produced in very large amount as byproduct from biodiesel synthesis [17]. With this background, 3-ethyl-5-benzylhydantoin (3a) [9] (R1 = CH2Ph and R2 = CH2CH3) was also prepared using solid MeO-PEG-2000-OMe and HO-PEG-3400-OH as additives (Table 2). Using (L)-H-Phe-OMe.HCl as substrate, as a

• general trend and in comparison with the dry-grinding procedure previously reported [9] (Table 2, entry 1), yields were generally lower with PEG additives, independently on their size and amounts (Table 2). This trend, apparently in contrast with the results illustrated so far for 3-ethyl-5