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

Formation of an unexpected 3,3-diphenyl-3H-indazole through a facile intramolecular [2 + 3] cycloaddition of the diazo intermediate

• Andrew T. King,
• Hugh G. Hiscocks,
• Lidia Matesic,
• Mohan Bhadbhade,
• Roger Bishop and
• Alison T. Ung

Beilstein J. Org. Chem. 2019, 15, 1347–1354, doi:10.3762/bjoc.15.134

• product was crystallised from dichloromethane to give a brown crystalline solid (0.064 g, 0.137 mmol, 27%); mp 183–184 °C; IR (neat) vmax/cm−1: 3057, 3025, 2959, 2926, 2650, 2322, 2112, 1943, 1591, 1490, 1470, 1445, 1349, 1263, 1205, 1127, 1023, 843, 748, 607; 1H NMR (500 MHz, CDCl3) δ 7.28–7.31 (m, H-Ar

Efficient resolution of racemic crown-shaped cyclotriveratrylene derivatives and isolation and characterization of the intermediate saddle isomer

• Sven Götz,
• Andreas Schneider and
• Arne Lützen

Beilstein J. Org. Chem. 2019, 15, 1339–1346, doi:10.3762/bjoc.15.133

• corresponds to the saddle conformer and is marked with 1-S. a) 1H NMR spectrum of the neat crown isomers of (rac)-1 in CD3OD (400 MHz, 298 K); b) 1H NMR spectrum in CD3OD (400 MHz, 298 K) of a sample of (rac)-1 after heating it to 200 °C in DMSO and quenching the solution by pouring it into an ice water

Understanding the unexpected effect of frequency on the kinetics of a covalent reaction under ball-milling conditions

• Ana M. Belenguer,
• Adam A. L. Michalchuk,
• Giulio I. Lampronti and
• Jeremy K. M. Sanders

Beilstein J. Org. Chem. 2019, 15, 1226–1235, doi:10.3762/bjoc.15.120

• less expensive than traditional solution-based methods, because they require little or no solvent. Moreover, mechanochemical syntheses often give quantitative yields of products [2][3][4]. Manual or mechanical grinding can be performed “neat”, i.e., in the absence of solvent (neat grinding, NG

• Information File 2), which we selected here to fit the experimental curve for 15 Hz ball-mill neat grinding. If a model is built on Scheme 2, with k1, k1' k2, Figure 2A is generated. Remarkably, despite the simplifying assumptions used in this model, the general features of the experimental curve are well

• by its ability to facilitate mass transport. Having ascertained that the model of Equation 4 well describes the non-linear kinetics observed for neat grinding, it is worth considering this model with respect to LAG kinetics. While the non-linearity is not so evident under LAG conditions, the

Mechanochemical amorphization of chitin: impact of apparatus material on performance and contamination

• Thomas Di Nardo and
• Audrey Moores

Beilstein J. Org. Chem. 2019, 15, 1217–1225, doi:10.3762/bjoc.15.119

• demonstrated as potential issue for milling. Milling is considered a neat method, yielding clean products but careful considerations must be taken when selecting milling media for this reason as well. Experimental Chemicals Practical grade chitin was purchased from Sigma-Aldrich Co. LLC (St-Louis, MO). Milling

Ugi reaction-derived prolyl peptide catalysts grafted on the renewable polymer polyfurfuryl alcohol for applications in heterogeneous enamine catalysis

• Alexander F. de la Torre,
• Gabriel S. Scatena,
• Oscar Valdés,
• Daniel G. Rivera and
• Márcio W. Paixão

Beilstein J. Org. Chem. 2019, 15, 1210–1216, doi:10.3762/bjoc.15.118

• attributed to the typical amide vibrations and are not present in neat PFA. In addition, the bands at around 800, 740 and 600 cm−1 confirm the presence of a 2,5-disubstituted furan ring typical of the PFA polymeric matrix [18]. The thermo-oxidative degradation of polymeric catalysts 3 and 4 was also examined

• using TGA, and compared with that of PFA (see Supporting Information File 1). This analysis showed that both polymers 3 and 4 are quite stable up to 100 °C, but as expected, decompose earlier than neat PFA. Thus, as main difference a significant loss of mass is observed for 3 and 4 at the range of 100

• –300 °C, whereas neat PFA is still stable at that temperature. This first degradation can be attributed to the decomposition of the peptidic skeleton, while at around 300 °C the decomposition of the polymeric lattice matrix starts, also of PFA. This analysis further demonstrates the incorporation of

Mechanochemical synthesis of hyper-crosslinked polymers: influences on their pore structure and adsorption behaviour for organic vapors

• Sven Grätz,
• Sebastian Zink,
• Hanna Kraffczyk,
• Marcus Rose and
• Lars Borchardt

Beilstein J. Org. Chem. 2019, 15, 1154–1161, doi:10.3762/bjoc.15.112

• 35 minutes. After the synthesis, the resulting polymers were washed with 200 mL of water and 100 mL of ethanol and dried at 80 °C for 12 hours to yield a beige powder (denoted NG-HCP (neat grinding-HCP)). For more details on the experimental procedure see Supporting Information File 1. After

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• defined their photophysical behavior in neat acetonitrile (ACN) solution and in the presence of barium cations. Figure 1 shows the absorption spectra of dyes 4a–d measured at different concentrations (cM) of Ba(ClO4)2. All dye solutions have similar absorption profiles with a broad long wavelength band in

• that in neat CD3CN (Supporting Information File 1, Figure S9 and Figure S10). A common behavior demonstrated in Figure 2 was observed: the fluorescence quantum yield of all dyes (Table 1) decreases if the concentration of the Ba2+ ions increases, i.e., the formation of the trans-dye–Ba2+ complexes

Fabrication, characterization and adsorption properties of cucurbit[7]uril-functionalized polycaprolactone electrospun nanofibrous membranes

• Changzhong Chen,
• Fengbo Liu,
• Xiongzhi Zhang,
• Zhiyong Zhao and
• Simin Liu

Beilstein J. Org. Chem. 2019, 15, 992–999, doi:10.3762/bjoc.15.97

• ratio of PCL/CB[7] is 100:200), which is far higher than the CDs content in CD-functionalized nanofibers [13][14][15] and the calixarene content in the calixarene-functionalized nanofibers [20]. Figure 1 presents the SEM photographs and fiber diameter distributions of neat PCL and the PCL/CB[7

• ] nanofibers with various amounts of CB[7] (the information of compositions, diameter and morphology of electrospun nanofibers are collected in Supporting Information File 1, Table S1). The bead-free neat PCL nanofibers with an average fiber diameter (AFD) of 193 nm were successfully electrospun from the PCL

• solution in formic acid/DMF with lower concentration (8%, w/v, with respect to the total volume of formic acid and DMF). Furthermore, the diameter of about 57% PCL nanofibers is lower than 200 nm. Compared to the electrospun PCL nanofibers in reported literatures [12][15][16][17], the AFD of neat PCL

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• . In 2008, they have established a [2 + 2] photodimerization through solid-state grinding either in neat or liquid-assisted conditions [93]. To achieve 100% stereospecific products they considered resorcinol derivatives as hydrogen-bond donors for the photodimerization of 1,2-di(pyridin-4-yl)ethylene

• has been shown to proceed with excellent turnover numbers. Recently, Friščić and Cinčić with co-workers reported an elaborative study on the halogen bonding between 1,3,5-trifluoro-2,4,6-triiodobenzene and triphenylphosphine, -arsine, and -stibine under neat mechanochemical conditions or through

• organocatalysis using PhI (10 mol %)–mCPBA at ambient conditions as well as under neat mixing [115]. The N1,N1-dibenzylbenzene-1,2-diamine (Figure 27) which is an integrated system by the combination of aniline and N,N-dibenzylaniline led to the successful formation of 1-benzyl-2-phenyl-benzo[d]imidazole 48 under

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

• example of “in water” metathesis with a heterogenous catalytic system. Pauly et al. used alginate beads as a matrix to encapsulate the G-II catalyst for the RCM of substrate 31 and 33 (Scheme 7) [44]. Alginate amide beads perform best in neat water as they facilitate the diffusion of hydrophobic

• ammonium tags Classical metathesis catalysts such as G-II and HG-II are among the most active, stable and versatile ruthenium complexes. Despite their high activity and remarkable stability, they are sparingly soluble in neat water, thus challenging their use as homogeneous catalysts in pure water. To

• ][53]. Grubbs and co-workers were the first to introduce water-soluble catalysts which displayed metathesis activity in aqueous media [54]. In 1996, Grubbs et al. reported that complexes 1 and 2 catalyze the living opening polymerization of norbornene derivatives 35 and 36 in neat water. Interestingly

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

• β/α mixture was obtained when 2a was reacted with neat bromotrimethylsilane at room temperature. Bromination of 2b yielded a 10:1 β/α mixture of the anomeric bromide 7b [27]. The reaction between Nam (1a) and the bromide 7a was carried out in liquid SO2 and proceeded in high yields with the

Synthesis of C₃-symmetric star-shaped molecules containing α-amino acids and dipeptides via Negishi coupling as a key step

• Sambasivarao Kotha and
• Saidulu Todeti

Beilstein J. Org. Chem. 2019, 15, 371–377, doi:10.3762/bjoc.15.33

• , m/z): [M + Na]+ calcd for C51H63N3NaO12, 932.4304; found, 932.4302; IR (neat) : 3661, 2349, 1716, 1495, 1163, 1044, 755 cm−1. General procedure for the mono- and dipeptide products 11, 12 and 13 Negishi coupling product 10 was dissolved in dichloromethane/trifluoroacetic acid (CH2Cl2/TFA 1:1) and

• , 127.6, 125.0, 53.6, 52.6, 37.7 ppm; HRMS–ESI (Q-Tof, m/z): [M + H]+ calcd for C51H46N3O9S3, 940.2391; found, 940.2392; IR (neat) : 3769, 3327, 2932, 1664, 1169, 759 cm−1. Dipeptide 12 Colorless solid; yield 73% (97 mg, starting from 100 mg of 10); Rf = 0.59 (6:4 ethyl acetate/petroleum ether); mp <230

• , J = 6.8 Hz, 9H), 0.87 (d, J = 4.0 Hz, 9H) ppm; 13C NMR (100 MHz, CDCl3) δ 171.8, 171.5, 155.9, 141.9, 139.9, 135.3, 129.8, 127.5, 124.9, 79.9, 60.0, 53.2, 52.4, 37.8, 31.0, 28.4, 19.3, 17.8 ppm; HRMS–ESI (Q-Tof, m/z): [M + Na]+ calcd for C66H90N6NaO15, 1229.6356; found, 1229.6359; IR (neat) : 3342

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

• was used as solvent with an 8.9% increase at 420 min. This affected the other performance indicators, i.e., PMPs, S, TON and TOF; lower values than the neat reactions were obtained. The results suggest that no significant solvent effect appears to exist .However, the increase in SMPs (associated with

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

• of N,N-dimethallyl-N-tosylamide (93) only 2 mol % of 85 were required to produce 54% of the tetrasubstituted tosylamide 94 within 3 h (Scheme 10). Moreover, catalyst 85 was quite efficient under neat conditions for the self metathesis of allylbenzene (13), showing no trace of isomerized byproducts

• saturated NHC ligand containing a N-substituted cyclododecyl side chain was first evaluated at 50 ppm loading in the self metathesis of 1-octene (96), at 50 °C under neat conditions, in comparison to symmetrical benchmark second-generation ruthenium catalysts IndII-SIMes, IndII-IMes, GII-SIMes and HGII

• distribution with no isomerization was observed without the use of any additive even after 24 h of reaction performed at 50 °C under neat conditions. N-Alkyl substituents possessing functionalities or heteroatoms In 2001, the Fürstner group reported on phosphine-containing ruthenium complexes having

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

• reaction mixture was allowed to cool to room temperature and then concentrated in vacuo. The residue was purified by column chromatography on silica gel (hexane/ethyl acetate 60:40) to provide the CM product (E)-N-benzyloxy)undec-2-enamide (6a, 133 mg, 81%) as a colourless viscous liquid. IR (neat): 3183

• 85 °C; IR (neat): 3259, 3058, 2956, 1663, 1624 cm−1; 1H NMR (400 MHz, DMSO-d6) δ 10.52 (s, 1H, NH), 8.93 (brs, 1H, OH), 1.92 (t, J = 7.2 Hz, 2H, C2-H), 1.44 (m, 2H, C3-H), 1.19 (s, 14H, 7× CH2), 0.81 (t, J = 6.8 Hz, 3H, C11-H); 13C NMR (100 MHz, DMSO-d6) δ 170.4 (CO), 32.6 (C2), 31.6 (C3), 29.3 (CH2

Nucleofugal behavior of a β-shielded α-cyanovinyl carbanion

• Rudolf Knorr and
• Barbara Schmidt

Beilstein J. Org. Chem. 2018, 14, 3018–3024, doi:10.3762/bjoc.14.281

• –30 °C under argon gas cover during the addition of n-BuLi (1.05 mmol) in hexane (0.47 mL). The created LDA (up to 1.05 mmol) solution was treated with the solid nitrile 1 (200 mg, 0.95 mmol) and stirred further at rt till 1 was completely dissolved, whereupon the carbonyl compound (1.24 mmol, neat or

Stereodivergent approach in the protected glycal synthesis of L-vancosamine, L-saccharosamine, L-daunosamine and L-ristosamine involving a ring-closing metathesis step

• Pierre-Antoine Nocquet,
• Aurélie Macé,
• Frédéric Legros,
• Jacques Lebreton,
• Gilles Dujardin,
• Sylvain Collet,
• Arnaud Martel,
• Bertrand Carboni and
• François Carreaux

Beilstein J. Org. Chem. 2018, 14, 2949–2955, doi:10.3762/bjoc.14.274

• ) [35]. Indeed, the reaction of achiral pinacol (Z)-crotylboronate with 5 under neat conditions at room temperature gave a good level of diastereoselectivity for the hitherto unreported 3,4-syn-2,3-anti product 12b [36][37][38][39]. The syn relationship between C3 and C4 is controlled by the (Z

MoO₃ on zeolites MCM-22, MCM-56 and 2D-MFI as catalysts for 1-octene metathesis

• Hynek Balcar,
• Martin Kubů,
• Naděžda Žilková and
• Mariya Shamzhy

Beilstein J. Org. Chem. 2018, 14, 2931–2939, doi:10.3762/bjoc.14.272

• MoO3 and/or MoO2(acac)2 on MWW zeolites (MCM-22, delaminated MCM-56) and on two-dimensional MFI (all in NH4+ form). The catalysts‘ activities were tested in the metathesis of neat 1-octene (as an example of a longer chain olefin) at 40 °C. Catalysts with 6 wt % or 5 wt % of Mo were used. The acidic

• supported MoO3 and/or MoO2(acac)2 on (i) 2D-MFI (and ordinary HZSM-5 for comparison) and similarly on (ii) MCM-56 and its 3D analogue MCM-22 (both in NH4+ form) and examined their activity in the metathesis of neat 1-octene (Scheme 1) under ambient pressure and 40 °C. According to our best knowledge, none

• molybdenum oxide metathesis catalysts. The catalysts, prepared by thermal spreading of MoO3 and/or MoO2(acac)2 on these supports in NH4+ forms (6 wt % and/or 5 wt % of Mo) were tested in neat 1-octene metathesis under mild conditions (batch reactor, atmospheric pressure, 40 °C). The catalyst activity

Synthesis of functionalised β-keto amides by aminoacylation/domino fragmentation of β-enamino amides

• Pavel Yanev and
• Plamen Angelov

Beilstein J. Org. Chem. 2018, 14, 2602–2606, doi:10.3762/bjoc.14.238

• behaviour. Domino fragmentation of α-aminoacyl intermediates 3 to N-protected γ-amino-β-ketoamides 5 Initially we tried a procedure developed earlier by us for simpler β-keto amides (30 min in neat TFA, then aqueous NaOAc) [22]. In contrast to the preparation of non-functionalised β-keto amides, here these

• mainly on the duration of the exposure of 3 to acid. Given enough time, the treatment in neat or diluted TFA led to a complete transformation of 3a–f into 6 without formation of the desired β-keto amides 5a–f at all. On the contrary – when the deprotection was carried out for 5 min in neat TFA, the

• favourable 5-exo-trig process, leading eventually to the pyrrolin-4-ones 6. This hypothesis is strongly supported by the behaviour of analogues 9 in which the auxiliary amino group is absent (Scheme 5). Under identical conditions (neat TFA, rt) compounds 9 do not react even after 12 hours. A reaction occurs

Design and synthesis of C₃-symmetric molecules bearing propellane moieties via cyclotrimerization and a ring-closing metathesis sequence

• Sambasivarao Kotha,
• Saidulu Todeti and
• Vikas R. Aswar

Beilstein J. Org. Chem. 2018, 14, 2537–2544, doi:10.3762/bjoc.14.230

• , 6H), 6.28 (s, 6H), 3.51–3.44 (m, 12H), 1.79 (d, J = 8.8 Hz, 3H), 1.61 (d, J = 8.8 Hz, 3H) ppm; 13C NMR (125 MHz, CDCl3) δ 177.0, 141.8, 141.3, 134.8, 131.4, 128.2, 127.2, 125.7, 52.4, 46.0, 45.7 ppm; HRMS (ESI, Q-ToF) m/z: [M + H]+ calcd for C51H40N3O6, 790.2912; found, 790.2918; IR (neat) max: 2918

• , 175.4, 136.7, 136.2, 136.1, 129.2, 126.5, 116.3, 49.1, 46.4, 35.4, 26.8 ppm; HRMS (ESI, Q-ToF) m/z: [M + Na]+ calcd for C19H19NO3·Na, 332.1257; found, 332.1254; IR (neat) max: 2325, 1671, 1263, 746 cm−1. Synthesis of trimerized compound 12 Based on the earlier procedure of trimerization, compound 13

• , 131.4, 128.1, 126.9, 125.6, 116.1, 49.1, 46.3, 35.5 ppm; HRMS (ESI, Q-ToF) m/z: [M + Na]+ calcd for C57H51N3O6·Na, 896.3670; found; 896.3678; IR (neat) max: 2342, 1709, 1512, 1183, 919, 736 cm−1. Synthesis of trimerized product 19 Based on the earlier procedure of trimerization, compound 18 (500 mg

Quinolines from the cyclocondensation of isatoic anhydride with ethyl acetoacetate: preparation of ethyl 4-hydroxy-2-methylquinoline-3-carboxylate and derivatives

• Nicholas G. Jentsch,
• Jared D. Hume,
• Emily B. Crull,
• Samer M. Beauti,
• Amy H. Pham,
• Julie A. Pigza,
• Jacques J. Kessl and
• Matthew G. Donahue

Beilstein J. Org. Chem. 2018, 14, 2529–2536, doi:10.3762/bjoc.14.229

• the undesired quinoline 12. We then turned to a functional group transformation of the ethyl ester at the 3-position to address the acetic acid sidechain problem (Scheme 7). First, the 4-hydroxy group in quinoline 10f was substituted for chlorine with neat phosphorus oxychloride to afford chloride 14

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• alkynes with azobenzenes 1 to synthesize dialkenated products 2 (Scheme 4) [32]. The reaction resulted in an anti-addition of the C–H bond with alkynes using the cobalt(I) catalysts CoH(N2)(PPh3)3 or CoH3(PPh3)3 under neat reaction conditions. After fifteen years, Yoshikai and co-workers developed a low

Studies towards the synthesis of hyperireflexolide A

• G. Hari Mangeswara Rao

Beilstein J. Org. Chem. 2018, 14, 2106–2111, doi:10.3762/bjoc.14.185

• = 13.2, 11.2 Hz, 1H), 2.11–2.04 (m, 1H), 1.50 (s, 3H, Me), 1.47 (s, 3H, Me), 1.37 (s, 3H, Me); 13C NMR (100 MHz, CDCl3) δ 203.4 (C=O), 171.0, 167.7, 84.5, 58.0, 55.6, 52.8, 44.9, 35.1, 29.3, 22.3, 18.7; IR (neat): 2900, 1760, 1740, 1440 cm−1; HRMS (m/z): [M]+ calcd for C12H16O5, 240.0998; found, 240.1001

• , Me), 1.49 (s, 3H, Me), 1.36 (s, 3H, Me); 13C NMR (100 MHz, CDCl3) δ 201.4 (C=O), 169.3, 168.4, 80.2, 59.2, 56.4, 53.5, 44.4, 36.5, 28.7, 22.6, 19.8, 18.7; IR (neat): 2900, 1760, 1740, 1440 cm−1; HRMS (m/z): [M]+ calcd for C13H18O5, 254.1154; found, 254.1155. Methyl 5-allyl-1,1-dimethyl-3,4

• –2.30 (m, 1H), 2.25–2.20 (m, 1H), 1.50 (s, 3H, Me), 1.44 (s, 3H, Me); 13C NMR (125 MHz, CDCl3) δ 202.6, 169.9, 167.8, 131.8, 120.2, 84.8, 61.8, 56.2, 53.0, 44.5, 37.3, 31.2, 29.4, 22.3; IR (neat): 2900, 1760, 1720, 1420 cm−1; HRMS (m/z): [M]+ calcd for C14H18O5, 266.1154; found, 266.1150. Methyl 5-allyl

Assessing the possibilities of designing a unified multistep continuous flow synthesis platform

• Mrityunjay K. Sharma,
• Roopashri B. Acharya,
• Chinmay A. Shukla and
• Amol A. Kulkarni

Beilstein J. Org. Chem. 2018, 14, 1917–1936, doi:10.3762/bjoc.14.166

• covered here from the case studies, where two reactants 2-dimethylaminoethanol and neat chlorodiphenylmethan is being pumped from P1 and P2 to reactor R1 where it is getting heated at a temperature of 180 °C at a pressure of 1.7 MPa. The molten salt which comes out of reactor R1 is then treated with