Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• ]. Such a geometry affects compatibility with the surrounding matrix. Thus, aggregation phenomena dominate in the case of IV. On the other hand, absorbers related to V often exhibit a much better solubility in organic surroundings such as multi-functional acrylates [5]. This can be seen as a huge

• surroundings is the biggest challenge in practical applications of these systems. Thus, counter ions such as n-C12H25-Ph-SO3− (8, 10, 79, 81), NTf2− (4) or [Al(OC4F9)4]− (37) depict alternatives resulting in a solubility of 10–30 g/L in reactive monomers such as multifunctional acrylates [5], printing inks or

• coating, where they properly helped to melt and cure the applied powder monomers nearly just in one step [16]. Typical monomers used in CtP, liquid coatings and powder coatings derive from urethane (meth)acrylates, epoxy (meth)acrylates, polyester(meth)acrylates or polyether (meth)acrylates. Literature

Synthesis of 3-alkenylindoles through regioselective C–H alkenylation of indoles by a ruthenium nanocatalyst

• Abhijit Paul,
• Debnath Chatterjee,
• Srirupa Banerjee and
• Somnath Yadav

Beilstein J. Org. Chem. 2020, 16, 140–148, doi:10.3762/bjoc.16.16

• reaction was also carried out using [Ru(p-cymene)Cl2]2 as a homogeneous catalyst, but this also did not lead to the formation of the desired product. After establishing the optimum conditions for the reaction, we carried out the alkenylation of several indole derivatives 1 with different acrylates 2 under

Functionalization of the imidazo[1,2-a]pyridine ring in α-phosphonoacrylates and α-phosphonopropionates via microwave-assisted Mizoroki–Heck reaction

• Damian Kusy,
• Agata Wojciechowska,
• Joanna Małolepsza and
• Katarzyna M. Błażewska

Beilstein J. Org. Chem. 2020, 16, 15–21, doi:10.3762/bjoc.16.3

• -bromoimidazo[1,2-a]pyridin-3-yl)-2-(diethoxyphosphoryl)acrylates 1, no desired product 3 was formed under standard heating conditions (Table 1, entry 1). Recently, multiple variants for the application of microwave heating for conducting Mizoroki–Heck reactions have been reported, including the use of

• )acrylate (analogs 1) or 2-(diethoxyphosphoryl)propanoates (analogs 2). The reaction worked well for a number of acrylates (Scheme 1), providing predominantly products with (E)-geometry of the newly formed double bond (E/Z ratio is above 98:2). Only for analog 11, the formation of the (Z)-product was

• -(bromoimidazo[1,2-a]pyridin-3-yl)-2-(diethoxyphosphoryl)acrylates 1 and propionates 2 using microwave-assisted Mizoroki–Heck reaction. The method worked for a number of olefins, enabling the functionalization of the heterocyclic ring with diverse groups, which can be used for further modifications. Importantly

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• peptidyl nucleosides with primarily antifungal properties. The stereoselective synthesis of (+)-polyoxamic acid ((2S,3S,4S)-144) was successfully carried out starting with Horner–Wadsworth–Emmons olefination of the aziridine aldehyde (2R,1'R)-6 which provided a 98:2 mixture of trans- and cis-acrylates 69b

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• obtained after cleavage of 84 under basic conditions. From pyroglutamic acid In case of low availability of selected stereoisomers of 4-hydroxyprolines asymmetric syntheses of enantiomeric 4-hydroxypyroglutamates have been elaborated employing 1,3-dipolar cycloadditions of homochiral nitrones and acrylates

Cross metathesis-mediated synthesis of hydroxamic acid derivatives

• Shital Kumar Chattopadhyay,
• Subhankar Ghosh and
• Suman Sil

Beilstein J. Org. Chem. 2018, 14, 3070–3075, doi:10.3762/bjoc.14.285

• CM-mediated synthesis of functionalized alkenes of various kinds continue to appear. For example, cross metathesis with acrylates [8][9][10], α,ß-unsaturated acid chlorides [11], acrylamides [12][13][14], vinyl sulfones [15], vinylphosphine oxides [16], vinyl phosphonates [17], enones [18], and

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• produced to initiate the polymerization. By formation of radicals, the polymerization of C=C functions such as (meth)acrylates or styrene can be initiated. With cations or acids as initiating species, epoxy monomers can be polymerized. Both types of polymerization are widely used both in academic and

• , formations of interpenetrated polymer networks (IPN) are also mentioned. For the three systems proposed above, formation of aryl radicals is observed. These radicals are able to initiate the free radical polymerization of (meth)acrylates [1]. In the photocatalytic cycle (Figure 5C), EDB(−H)• radicals are

• infrared spectroscopy, following the epoxy function. Other monomers presented in Scheme 6 are acrylates and methacrylates and can be polymerized by free radical polymerization. Photopolymerization of these compounds can also be characterized by FTIR measurement, following the C=C double bound conversion

Ring-closing-metathesis-based synthesis of annellated coumarins from 8-allylcoumarins

• Christiane Schultze and
• Bernd Schmidt

Beilstein J. Org. Chem. 2018, 14, 2991–2998, doi:10.3762/bjoc.14.278

• , we investigated the synthesis of coumarins with annellated unsaturated lactones starting from the same 8-allylcoumarins 8 (Scheme 1). For the synthesis of oxepin-2-one-annellated coumarins 13 compounds 8 were first converted to the corresponding acrylates 12 with acryloyl chloride (Table 3). RCM of

• these acrylates turned out to be not straightforward but required some optimization (Table 4). In particular, a reduced initial substrate concentration of 0.01 M and reaction temperatures of 110 °C (Table 4, entry 6) led to a smooth conversion to the desired oxepin-2-ones 13, whereas ambient or slightly

• completely in this case (Table 4, entries 3 and 4). The beneficial effect of low initial substrate concentrations on RCM reactions with acrylates has previously been described [65] and was later systematically investigated by one of us [66]. A possible access to the pyran-2-one-annellated coumarin

Synthesis of unnatural α-amino esters using ethyl nitroacetate and condensation or cycloaddition reactions

• Glwadys Gagnot,
• Vincent Hervin,
• Eloi P. Coutant,
• Sarah Desmons,
• Racha Baatallah,
• Victor Monnot and
• Yves L. Janin

Beilstein J. Org. Chem. 2018, 14, 2846–2852, doi:10.3762/bjoc.14.263

• acetic anhydride afforded a mixture of compounds containing variable amounts of the expected acrylates 2a–s. No attempts were made to purify these as they were immediately subjected to a reduction of its double bond using sodium borohydride [9][10] in refluxing isopropanol in order to properly isolate

• . Indeed, the best overall yields are observed when starting from the electronically similar 2-methoxy acetal 5b or the 4-methoxy analog 5d, as well as the 4-benzyloxy acetal 5e. (ii) Secondly, the reduction of acrylates 2a–s to compounds 6a–s was achieved with sodium borohydride and the resulting basic

• conditions could be detrimental to the stability of some of these α-nitro acrylates. In the past, such reductions have been achieved under fairly uncommon conditions (NaBH4 in a mixture of isopropanol and chloroform over a large proportion of silica gel) [11][12]. However, when tried, no real overall

DABCO- and DBU-promoted one-pot reaction of N-sulfonyl ketimines with Morita–Baylis–Hillman carbonates: a sequential approach to (2-hydroxyaryl)nicotinate derivatives

• Soumitra Guin,
• Raman Gupta,
• Debashis Majee and
• Sampak Samanta

Beilstein J. Org. Chem. 2018, 14, 2771–2778, doi:10.3762/bjoc.14.254

• generality and scope of the reaction by reacting several aryl/heteroaryl-substituted MBH carbonates derived from acrylates 2a–j and 4-methyl-N-sulfonyl ketimines 1a–e under present sequential reaction conditions. The results are incorporated in Scheme 3. The regioselective allylic alkylation/aromatization

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• (III) form of 1 has recently been found to catalyze atom transfer radical addition of alkyl halides to olefins (phenyl vinyl sulfone and acrylates) in the presence of NaBH4 [115]. In addition, a new light-driven method for generating acyl radicals from 2-S-pyridyl thioesters was developed through the

Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source

• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221

• reductant, carboxyzincation and the four-component coupling reaction between alkyne, acrylates, CO2, and zinc occur efficiently. Rh complexes also catalyze the carboxylation of arylboronic esters, C(sp2)–H carboxylation of aromatic compounds, and hydrocarboxylation of styrene derivatives. The Rh-catalyzed

• carboxylation of allylarenes when a suitable ligand is used. In the presence of zinc powder, the Co-catalyzed carboxyzincation of alkynes and the four-component coupling reaction between alkyne, acrylates, CO2, and zinc proceed in an efficient manner. Visible-light-driven hydrocarboxylation reactions are shown

• , thereby giving the carboxyzincated product and regenerating Co(I) species A (step c). We also achieved the four-component coupling of alkynes 16, acrylates 18, CO2, and Zn metal, as depicted in Scheme 18 [40]. As a model reaction, the reaction using diphenylacetylene (16h), butyl acrylate (18a), CO2, and

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

• Gwendal Grelier,
• Benjamin Darses and
• Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

• –I motif (Scheme 22) [62]. Hence aryl- and alkyl-substituted terminal alkynes can be coupled via a Sonogashira reaction when PPh3 is used as ligand, while the use of diphenylphosphinoferrocenyl ligand (dppf) allows the Heck-type coupling of acrylates, vinyl ketones and electron-poor styrene

Bromide-assisted chemoselective Heck reaction of 3-bromoindazoles under high-speed ball-milling conditions: synthesis of axitinib

• Jingbo Yu,
• Zikun Hong,
• Xinjie Yang,
• Yu Jiang,
• Zhijiang Jiang and
• Weike Su

Beilstein J. Org. Chem. 2018, 14, 786–795, doi:10.3762/bjoc.14.66

• corresponding coupling products 3aa and 3af in considerable yields. The scope of the reaction with respect to the olefins was also extensively investigated and encompasses acrylates 2a, acrylamides 2b and 2c, styrenes 2f–m and 2-vinylpyridine (2n). In addition, even non-activated allylbenzene 2o and

Cobalt-catalyzed directed C–H alkenylation of pivalophenone N–H imine with alkenyl phosphates

• Wengang Xu and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2018, 14, 709–715, doi:10.3762/bjoc.14.60

• (e.g., acrylates), and is challenging with unactivated and multisubstituted alkenes [11]. The hydroarylation of alkynes does not allow for the introduction of cycloalkenyl groups because of the unavailability of the corresponding alkynes. In light of such limitations, a coupling between arene

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

Spatial effects in polymer chemistry

• Helmut Ritter

Beilstein J. Org. Chem. 2017, 13, 2015–2016, doi:10.3762/bjoc.13.198

• the carbonyl group of, e.g., poly(acrylates) show different IR signals when positioned side by side. If, for example, they are separated by styryl units, these carbonyl signals are clearly shifted. Such effects also play an important role in the reactivity of, e.g., ester-side groups. For example, the

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• . They have also demonstrated a mechanochemical synthesis of 3-vinylindoles and β,β-diindolylpropionates by C–H activation. Substituted indoles and ethyl acrylates were reacted in presence of 10 mol % of Pd(OAc)2 and 1.2 equiv of MnO2 to afford highly substituted 3-vinylindoles using silica gel and

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

• sulfoxide substituent. Compounds 2 and 3 were obtained by us earlier [23] in diastereomerically pure form as key intermediates in our approach to constrained phosphonic acids by the reaction of phosphoryl acrylates with (S)-dimethylsulfonium(p-tolylsulfinyl)methylide. The carboxylate moiety was geminal to

Detection of therapeutic radiation in three-dimensions

• John A. Adamovics

Beilstein J. Org. Chem. 2017, 13, 1325–1331, doi:10.3762/bjoc.13.129

• their effective atomic number is not tissue equivalent. Acrylates, polyesters, polystyrenes and polycarbonates were also eliminated due to the relatively high exotherms created (>100 °C) during polymerization which prematurely oxidize the leuco dyes and rendered the dosimeter product unusable due to

Highly reactive, liquid diacrylamides via synergistic combination of spatially arranged curing moieties

• Maximilian Maier,
• Magnus S. Schmidt,
• Markus Ringwald and
• Christoph P. Fik

Beilstein J. Org. Chem. 2017, 13, 372–383, doi:10.3762/bjoc.13.40

• of new monomers and crosslinkers remained limited [4]. Mono-, di-, tri- and multifunctional (meth)acrylates are among the first choices for photopolymerized mixtures as they exhibit a favorable balance between reactivity and thermal stability upon storage [5][6][7]. Moreover, they comprise

3D printed fluidics with embedded analytic functionality for automated reaction optimisation

• Andrew J. Capel,
• Andrew Wright,
• Matthew J. Harding,
• George W. Weaver,
• Yuqi Li,
• Russell A. Harris,
• Steve Edmondson,
• Ruth D. Goodridge and
• Steven D. R. Christie

Beilstein J. Org. Chem. 2017, 13, 111–119, doi:10.3762/bjoc.13.14

• roughness and difficulty with removing un-melted powder from smaller cavities [6]. SL utilises layer-by-layer photopolymerisation of a liquid resin bath to generate fully dense polymer parts [21]. Typically these resins are complex formulations based around a small selection of UV-curable acrylates, epoxies

Iodination of carbohydrate-derived 1,2-oxazines to enantiopure 5-iodo-3,6-dihydro-2H-1,2-oxazines and subsequent palladium-catalyzed cross-coupling reactions

• Michal Medvecký,
• Igor Linder,
• Luise Schefzig,
• Hans-Ulrich Reissig and
• Reinhold Zimmer

Beilstein J. Org. Chem. 2016, 12, 2898–2905, doi:10.3762/bjoc.12.289

• -oxazine syn-11 in 41% yield. Next, we briefly studied 5-iodo-1,2-oxazine syn-4a as substrate in Heck reactions. The substrate was reacted with the alkyl acrylates 12a (R1 = Me) and 12b (R1 = t-Bu) under phosphine-free conditions [33][34] using 6 mol % of palladium(II) acetate, triethylamine as base and

• lithium chloride [35] leading to the expected coupling products syn-13 and syn-14 in 39% and 82% yield, respectively (Scheme 5). In both cases, only the E-configured 2-substituted alkyl acrylates were isolated. The moderate yield in the Heck reaction with methyl acrylate 12a is very likely caused by the

Experimental and theoretical insights in the alkene–arene intramolecular π-stacking interaction

• Valeria Corne,
• Ariel M. Sarotti,
• Carmen Ramirez de Arellano,
• Rolando A. Spanevello and
• Alejandra G. Suárez

Beilstein J. Org. Chem. 2016, 12, 1616–1623, doi:10.3762/bjoc.12.158

• , spectroscopic and computational evidence of the structurally related chiral acrylates to get new insights into the alkene–arene intramolecular interaction. Besides, it was evaluated the effect of the electron density of the aromatic counterpart and its influence on the asymmetric inductive capacity of the

• 40:60. The diastereomeric mixture of 4 and 5 was easily separated by flash chromatography. Finally, acrylates 6a,b were prepared by reaction of the corresponding alcohol 5 with acryloyl chloride in the presence of Et3N at 0 °C. The corresponding acrylic ester could not be obtained from the epimeric

• alcohols 4, probably because of the steric hindrance surrounding the alcohol position. Therefore, alcohols 4 were recycled by oxidation with PCC regenerating 3 in very good yields, and increasing the overall yield of acrylates 6. The 1H NMR spectra of compounds 6a and 6b (300 MHz, CDCl3) showed an