A heteroditopic macrocycle as organocatalytic nanoreactor for pyrroloacridinone synthesis in water

• Piyali Sarkar,
• Sayan Sarkar and
• Pradyut Ghosh

Beilstein J. Org. Chem. 2019, 15, 1505–1514, doi:10.3762/bjoc.15.152

• sites along with H-bonding donor/acceptor site. So, it may also be associated to the nanoreactor to approach the enaminoketone. Then, consecutive cyclization and ring opening of isatin (translactamization) affords intermediate C which undergoes cyclocondensation to furnish the final product F

Borylation and rearrangement of alkynyloxiranes: a stereospecific route to substituted α-enynes

• Ruben Pomar Fuentespina,
• José Angel Garcia de la Cruz,
• Gabriel Durin,
• Victor Mamane,
• Jean-Marc Weibel and
• Patrick Pale

Beilstein J. Org. Chem. 2019, 15, 1416–1424, doi:10.3762/bjoc.15.141

• ] transferring the non-oxygenated boron substituent and promoting oxirane ring opening [39]. The group’s migratory aptitude cannot be directly compared to that known from cationic rearrangements, because the nature of the other boron substituents plays a key role in migration, as revealed by calculations [40][41

• B could be envisaged with the large pinacol substituent facing the small oxirane ring and thus placing the migrating group antiparallel to the adjacent oxiranyl C–O bond. This may explain the role of the diol substituent on the reaction efficacy (see Table 1). Upon migration and oxirane ring opening

One-pot activation–alkynylation–cyclization synthesis of 1,5-diacyl-5-hydroxypyrazolines in a consecutive three-component fashion

• Christina Görgen,
• Katharina Boden,
• Guido J. Reiss,
• Walter Frank and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 1360–1370, doi:10.3762/bjoc.15.136

• -acyl-5-hydroxypyrazoline acts as a bidentate ligand [31]. Upon treatment with TMEDA mononuclear complexes with concomitant ring opening to give a seven-membered bidentate chelate are generated. Although numerous syntheses of pyrazolines [3][4][5] in general and 1-acyl-5-hydroxypyrazolines [24][25][26

Anomeric sugar boronic acid analogues as potential agents for boron neutron capture therapy

• Daniela Imperio,
• Erika Del Grosso,
• Silvia Fallarini,
• Grazia Lombardi and
• Luigi Panza

Beilstein J. Org. Chem. 2019, 15, 1355–1359, doi:10.3762/bjoc.15.135

• ester ring opening, while compound 11 demonstrated to be stable. The two compounds showed no toxicity on human primary fibroblasts. Further studies will be conducted to determine the cellular uptake of compounds 8 and 11. Structure of boronic acid analogues (for clarity, sugar numbering has been

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• formed by a concerted pathway. Then the fluoride induced ring opening and subsequent cyclization of intermediate 84 would generate phthalimide 79. Although most multicomponent reactions leading to isoindolinones make use of benzoic acid derivatives as one of the starting components, in a few

Mechanochemical synthesis of poly(trimethylene carbonate)s: an example of rate acceleration

• Sora Park and
• Jeung Gon Kim

Beilstein J. Org. Chem. 2019, 15, 963–970, doi:10.3762/bjoc.15.93

• Discussion Aliphatic polycarbonates are found in many biomedical applications since they have many desirable properties such as high biocompatibility, easy degradation, good mechanical properties, and low toxicity [21][22][23]. Many synthetic methods have been developed, and the chain-growth ring-opening

• biomedical applications [24]. The amidine base 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is one of the best studied and most popular organocatalysts for ring-opening polymerizations of cyclic carbonates and lactones [25][26][27]. In contrast to the high activity of lactone polymerization, cyclic carbonate

• improvement of reaction efficiency. The high impact collision energy [28][29] and exothermic nature of the given ring-opening polymerization [30] could increase the temperature of a ball-mill system, which would speed up the polymerization rate [31][32]. To gain insight into thermal effects, we monitored the

Synthesis of acylglycerol derivatives by mechanochemistry

• Karen J. Ardila-Fierro,
• Andrij Pich,
• Marc Spehr,
• José G. Hernández and
• Carsten Bolm

Beilstein J. Org. Chem. 2019, 15, 811–817, doi:10.3762/bjoc.15.78

• by epoxide ring-opening and esterification reactions with fatty acids 3 (Scheme 1). If successful, developing a multistep approach to prepare DAGs would contribute to the expansion of synthetic mechanochemical methodologies in ball mills [28][29][30][31], which are often limited to single-step

• hands, a selective epoxide ring-opening reaction with fatty acids 3 leading to the formation of the corresponding sn-1,3-protected monoacylglycerols (MAGs 4) was attempted (Scheme 3). Initially, commonly used solution-based protocols were tested in the ball mill [33]. For example, 2 was reacted with

• stearic acid (3a) in the presence of amines such as pyridine or tributylamine. However, the analysis of the reaction mixture only showed unreacted starting materials. In previous work, an acceleration of the oxirane ring-opening reaction with carboxylic acids [34] or alcohols [35] by using Lewis acid

Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors

• Kirill B. Polyanskii,
• Kseniia A. Alekseeva,
• Pavel V. Raspertov,
• Pavel A. Kumandin,
• Eugeniya V. Nikitina,
• Atash V. Gurbanov and
• Fedor I. Zubkov

Beilstein J. Org. Chem. 2019, 15, 769–779, doi:10.3762/bjoc.15.73

• by NMR, ESIMS, and X-ray crystallography. The utility of this chemistry is further demonstrated by the tests of the novel catalysts (up to 10−2 mol %) in different metathesis reactions such as cross metathesis (CM), ring-closing metathesis (RCM) and ring-opening cross metathesis (ROCM). Keywords: CM

• ; cross metathesis; Hoveyda–Grubbs catalyst; olefin metathesis; RCM; ring-closing metathesis; ring-opening cross metathesis; ROCM; ruthenium metathesis catalyst; styrene; 2-vinylbenzylamine; Introduction Ruthenium-catalysed olefin metathesis reactions have been playing an important role in various fields

• ][9][10][11][12], including most popular recent books [13][14]. Obviously, the application of various catalysts is required to achieve the best results in each of the many directions of metathesis reactions such as cross metathesis – CM, ring-opening metathesis – ROM, ring-closing metathesis – RCM

Diastereo- and enantioselective preparation of cyclopropanol derivatives

• Marwan Simaan and
• Ilan Marek

Beilstein J. Org. Chem. 2019, 15, 752–760, doi:10.3762/bjoc.15.71

• when the same sequence of diastereoselective carbometalation/oxidation was performed on cyclopropenyl ester 1, the in situ-formed donor–acceptor cyclopropanol undergoes a selective ring-opening to provide the acyclic product possessing a quaternary carbon stereocenter [57]. As the enantioselective

Dirhodium(II)-catalyzed [3 + 2] cycloaddition of N-arylaminocyclopropane with alkyne derivatives

• Wentong Liu,
• Yi Kuang,
• Zhifan Wang,
• Jin Zhu and
• Yuanhua Wang

Beilstein J. Org. Chem. 2019, 15, 542–550, doi:10.3762/bjoc.15.48

• ciprofloxacin and moxifloxacin (Scheme 1), and reverse transcriptase inhibitors [2], such as nevirapine. Meanwhile, since 1 contains a three-membered ring with high tension [3][4][5][6] and a nitrogen prone to single-electron oxidation, ring opening readily occurs followed by N-centered radical formation. The

• (Rh2(II,II)), that efficiently catalyzes the ring opening of 1 to achieve cycloaddition with alkene substrates under an argon atmosphere [18]. During the reaction, no metal valence changes were observed. We proposed that Rh2(II,II) may coordinate with the nitrogen in 1 to decrease the bond dissociation

• 3,5-dimethyl compound 1d afforded the desired product 3d with an excellent yield of 91% (Table 2, entry 3). We reasoned the electron-withdrawing groups on the arene increased the nitrogen–hydrogen bond dissociation energy (BDEN–H) of compound 1 [21], decreasing the rate of ring opening. Substrates 1i

Aqueous olefin metathesis: recent developments and applications

• Valerio Sabatino and
• Thomas R. Ward

Beilstein J. Org. Chem. 2019, 15, 445–468, doi:10.3762/bjoc.15.39

• publication, catalyst 9 was used for an aqueous living ring-opening metathesis polymerization-induced self-assembly (ROMPISA). The authors demonstrated the possibility of performing living ROMP in water selecting a quaternary ammonium-based phenyl norbornene carboximide as core-forming monomer [60]. This

• tags. c) PEG-tethered catalysts. Chemical structure and components of amphiphilic molecule PTS and derivatives. In vivo metathesis with an artificial metalloenzyme based on the biotin–streptavidin technology. Most common metathesis reactions. Ring-opening metathesis polymerization (ROMP), acyclic diene

• metathesis (ADMET), ring-closing metathesis (RCM), ring-opening metathesis (ROM), and cross-metathesis (CM). Catalytic cycle for metathesis proposed by Chauvin. First aqueous ROMP reactions catalyzed by ruthenium(III) salts. Degradation pathway of first generation Grubbs catalyst (G-I) in methanol. Synthesis

Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

• Mikhail V. Makarov and
• Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

• more concentrated alkaline conditions (5 N KOH) as a result of a pyridinium ring opening–closure process [57]. It was also shown that the ionization of a diol fragment of NAD+ under alkaline conditions plays a very important role in the dissociative cleavage of the glycosyl bond of the “northern

Annulation of 1H-pyrrole-2,3-diones by thioacetamide: an approach to 5-azaisatins

• Aleksandr I. Kobelev,
• Ekaterina E. Stepanova,
• Maksim V. Dmitriev and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2019, 15, 364–370, doi:10.3762/bjoc.15.32

• corresponding 1H-pyrrolo[3,2-c]pyridine-2,3-dione 4l. The most possible explanation of this fact is the steric hindrance introduced by the N-phenyl substituent, which obstructs the thiazole ring opening. Conclusion In summary, we have developed a novel approach to 1H-pyrrolo[3,2-c]pyridine-2,3-diones (5

Reusable and highly enantioselective water-soluble Ru(II)-Amm-Pheox catalyst for intramolecular cyclopropanation of diazo compounds

• Hamada S. A. Mandour,
• Yoko Nakagawa,
• Masaya Tone,
• Hayato Inoue,
• Nansalmaa Otog,
• Ikuhide Fujisawa,
• Soda Chanthamath and
• Seiji Iwasa

Beilstein J. Org. Chem. 2019, 15, 357–363, doi:10.3762/bjoc.15.31

• the catalyst leakage during the work-up. Synthetic transformations of 2d and 2f In order to demonstrate the advantages of products, further synthetic transformations of the cyclopropane products were investigated. A ring opening and direct amidation of the chiral cyclopropane-fused γ-lacton 2d using

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

• Guillaume Ernouf,
• Jean-Louis Brayer,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

• formation of the gem-dichloro-α-lactam intermediate 17f which would undergo ring opening by nucleophilic addition of pyrrolidine followed by hydrolysis of the resulting α,α-dichloro-α-aminoacetamide 18f (Scheme 12). To access aminocyclopropanes, the hydrogenation of (arylmethylene)cyclopropane 13f was

• were converted into α-allenic tertiary alcohols 22a–c (30–61%) The formation of alcohols 22a–c was explained by a mechanism involving ionization of the C4–O bond in imidates 21a–c, followed by ring opening of the alkylidenecyclopropyl cationic intermediates 23a–c [52] and addition of water to the

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

• Patrycja Żak and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

• silsesquioxanes (POSS) and POSS-containing polymeric materials. Three types of processes, i.e., cross metathesis (CM) of vinyl-substituted POSS with terminal olefins, acyclic diene metathesis (ADMET) copolymerization of divinyl-substituted POSS with α,ω-dienes and ring-opening metathesis polymerization (ROMP) of

• metathesis in chemistry of unsaturated derivatives of POSS is limited to three types of processes, i.e., cross metathesis (CM) of vinyl-substituted POSS with terminal olefins, acyclic diene metathesis (ADMET) copolymerization of divinyl-substituted POSS with α,ω-dienes and ring-opening metathesis

• to 11033 Da and polydispersity index (PDI) = 1.5. Ring-opening metathesis polymerization (ROMP) of POSS-functionalized monomers The chemistry of inorganic–organic hybrid materials has emerged as a fascinating new field of modern nanotechnology. The inclusion of POSS cages into the polymeric material

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• Yu Liu Qiao-Lin Wang Zan Chen Cong-Shan Zhou Bi-Quan Xiong Pan-Liang Zhang Chang-An Yang Quan Zhou Department of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, P. R. China 10.3762/bjoc.15.23 Abstract The ring-opening/cyclization of cyclopropane

• derivatives has drawn great attention in the past several decades. In this review, recent efforts in the development of oxidative radical ring-opening/cyclization of cyclopropane derivatives, including methylenecyclopropanes, cyclopropyl olefins and cyclopropanols, are described. We hope this review will be

• of sufficient interest for the scientific community to further advance the application of oxidative radical strategies in the ring-opening/cyclization of cyclopropane derivatives. Keywords: cyclopropane derivatives; free radicals; ring-opening/cyclization; Introduction Cyclopropane is a cycloalkane

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

• the aziridine (2R,1′S)-27 as a synthetic equivalent of L-serine (Scheme 7) [56]. Stereoselective reduction of ketone (2R,1′S)-28 gave hydroxyaziridine 29 as the major (10:1) product which, after the protection of the hydroxy group, was subjected to the regioselective aziridine ring opening, catalytic

• -hydroxyglutamate [(2S,4R)-81] (Scheme 20) [82]. To synthesize (2S,4S)-81 the inversion of configuration at C4 executed by Mitsunobu reaction preceded oxidation at C5 and the ring opening [82]. O-Benzyl ethers of (2S,4R)-3 and (2S,4S)-3 were prepared by the same methodology [50]. Another approach to the

• acid Cleavage of the 5-membered ring in the protected epoxide 88 obtained from (S)-pyroglutamic acid [93][94][95] gave the methyl ester 89 which, when adsorbed on silica gel, smoothly underwent stereospecific epoxide ring opening to give the oxazolidinone 90 (Scheme 23) [96]. Before installation of the

Olefin metathesis in multiblock copolymer synthesis

• Maria L. Gringolts,
• Yulia I. Denisova,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2019, 15, 218–235, doi:10.3762/bjoc.15.21

• across double C=C bonds. The main techniques, actively developed during the last decade and discussed here, are the coupling of end-functionalized blocks, sequential ring-opening metathesis polymerization, and cross metathesis between unsaturated polymers, or macromolecular cross metathesis. The last

• approaches to multiblock copolymer syntheses via olefin metathesis reactions developed mainly over the past ten years. The following sections address the achievements and perspectives of three main techniques used for this purpose, namely, sequential ring-opening metathesis polymerization, coupling of end

• -functionalized blocks, and macromolecular cross metathesis. Review Synthesis by sequential ring-opening metathesis polymerization Living ring-opening metathesis polymerization (ROMP) provides an opportunity to use a well-established route to multiblock copolymers based on the repetitive addition of different

Catalysis of linear alkene metathesis by Grubbs-type ruthenium alkylidene complexes containing hemilabile α,α-diphenyl-(monosubstituted-pyridin-2-yl)methanolato ligands

• Tegene T. Tole,
• Johan H. L. Jordaan and
• Hermanus C. M. Vosloo

Beilstein J. Org. Chem. 2019, 15, 194–209, doi:10.3762/bjoc.15.19

• (RCM) of dialkenes, ring-opening metathesis polymerisation (ROMP), isomerisation of alkenes and cross-metathesis (CM) of alkenes [7]. The complexes were synthesized by reacting the lithium salts of the corresponding pyridinyl alcohols with [RuCl2(=CHC6H5)(P(iPr3))2]. These complexes catalysed inter

Synthesis, biophysical properties, and RNase H activity of 6’-difluoro[4.3.0]bicyclo-DNA

• Sibylle Frei,
• Adam K. Katolik and
• Christian J. Leumann

Beilstein J. Org. Chem. 2019, 15, 79–88, doi:10.3762/bjoc.15.9

• -DNA (6’-diF-bc4,3-DNA). The difluorinated thymidine phosphoramidite building block was synthesized starting from an already known gem-difluorinated tricyclic glycal. This tricyclic siloxydifluorocyclopropane was converted into the [4.3.0]bicyclic nucleoside via cyclopropane ring-opening through the

• inseparable mixture of two diiodo-substituted products was unveiled. The major product was the bicyclic gem-diol 4 and the minor one the corresponding ketone 3. We hypothesize that the α,α-difluoroketone 3 was formed through a cyclopropane ring-opening followed by the addition of the electrophilic iodine in

Selective ring-opening metathesis polymerization (ROMP) of cyclobutenes. Unsymmetrical ladderphane containing polycyclobutene and polynorbornene strands

• Yuan-Zhen Ke,
• Shou-Ling Huang,
• Guoqiao Lai and
• Tien-Yau Luh

Beilstein J. Org. Chem. 2019, 15, 44–51, doi:10.3762/bjoc.15.4

• strand is 8:1. Keywords: cyclobutene; hydrolysis; linker; metathesis; norbornene; ROMP; selectivity; unsymmetrical ladderphane; Introduction Ring-opening metathesis polymerizations (ROMP) of strained cycloalkenes offer a powerful arsenal for the synthesis of polymers having a variety of fascinating

• and the olefinic proton of unreacted norbornene pendants, respectively. In the 13C NMR spectrum, the peak at δ 139 ppm owing to the olefinic carbon of cyclobutene shifts to δ 130 ppm due to ring opening, whereas the olefin carbon of the unreacted norbornene moiety at δ 136 ppm remained unchanged after

• relevant peaks. We have previously found that two norbornene derivatives connected by a flexible linker 15 may undergo cascade ring-opening–ring-closing metathesis polymerization to give single-stranded hammock-like appended polynorbornenes 17 (Scheme 6) [17][18]. The linker in 8 is flexible, and

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• substituent (Figure 15) at the nitrogen atoms were investigated by Copéret and Thieuleux et al. in the tandem ring-opening–ring-closing alkene metathesis (RO–RCM) of cis-cyclooctene (47) and their performance were compared to those of the classical GII-SIMes and GII-IMes [29]. The dissymmetry of the NHC

• catalysts 61, 64, 65, 67 and 68 (Figure 16) were also investigated in the model asymmetric ring-opening cross metathesis (AROCM) of cis-5-norbornene-endo-2,3-dicarboxylic anhydride (75) with styrene (Scheme 8, Table 3) [32]. In this reaction complex 68 showed the highest selectivity for the formation of the

6’-Fluoro[4.3.0]bicyclo nucleic acid: synthesis, biophysical properties and molecular dynamics simulations

• Sibylle Frei,
• Andrei Istrate and
• Christian J. Leumann

Beilstein J. Org. Chem. 2018, 14, 3088–3097, doi:10.3762/bjoc.14.288

• either by a NIS-mediated or Vorbrüggen nucleosidation yielded in both cases the β-tricyclic nucleoside as major anomer. Subsequent desilylation and cyclopropane ring opening of these tricyclic intermediates afforded the unsaturated 6’F-bc4,3 nucleosides. The successful incorporation of the corresponding

• enlargement via selective cyclopropane ring opening [46][47][48][49]. Consequently, the synthesis started from the previously described bicyclic silyl enol ethers 1α/β (Scheme 1) [50][51]. The two anomers of 1 were individually transformed into the trimethylsilyl (TMS)-protected sugars 2α/β by adapting and

• 6α/β were subjected to the next reaction step, where the simultaneous desilylation and cyclopropane ring opening to the bicyclic fluoroenone 7 occurred. HF-pyridine smoothly facilitated this conversion. At this stage the two anomers of fluoroenone 7 were separable. The configurational assignment of

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

• generation of silylium cations is possible. These cations have been described in the literature for initiation of ring-opening polymerization processes [25]. Cations Ph-NVK+ produced in catalytic cycle (Figure 5B) have also been well noted in the literature as highly reactive structures [26][27]. Amines

• absorption and redox properties through well selected ligands [52]. This Ir-based complex reacts in the photoredox catalytical cycle with iodonium salt and (TMS)3SiH as the Ru-based complex in reactions 1, 2 and 3. Moreover, Iridium complexes can be interesting for applications in ring-opening

• photopolymerization initiation as shown in [53] (see Part 3). For this purpose, the Ir complex was more interesting than the Ru one because of the longer excited state lifetime, lower oxidation potential leading to higher interaction rate constants with additives used for ring-opening photopolymerization (e.g