Design of a double-decker coordination cage revisited to make new cages and exemplify ligand isomerism

• Sagarika Samantray,
• Sreenivasulu Bandi and
• Dillip K. Chand

Beilstein J. Org. Chem. 2019, 15, 1129–1140, doi:10.3762/bjoc.15.109

• Sagarika Samantray Sreenivasulu Bandi Dillip K. Chand Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India 10.3762/bjoc.15.109 Abstract The complexation study of cis-protected and bare palladium(II) components with a new tridentate ligand, i.e., pyridine-3,5

• : anion binding; double-decker cage; ligand isomerism; macrocycles; palladium; self-assembly; supramolecular; Introduction Coordination-driven self-assembly is a convenient strategy for the construction of supramolecules of desired dimensions via simple synthetic procedures. Well-defined metal–ligand

• coordination bonds enable the construction of designer targeted molecules with ease. The use of a palladium(II) component for complexation with a non-chelating bi- or polydentate ligand (usually N-donor ligands) is particularly advantageous for the construction of a variety of metallocages [1][2][3][4][5

Electrophilic oligodeoxynucleotide synthesis using dM-Dmoc for amino protection

• Shahien Shahsavari,
• Dhananjani N. A. M. Eriyagama,
• Bhaskar Halami,
• Vagarshak Begoyan,
• Marina Tanasova,
• Jinsen Chen and
• Shiyue Fang

Beilstein J. Org. Chem. 2019, 15, 1116–1128, doi:10.3762/bjoc.15.108

• as linker to enable deprotection and cleavage under milder basic conditions [32]. The palladium-labile allyl groups were also used for amino protection [33][34]. The o-nitrobenzyl function was used as linker to enable photo cleavage [34]. However, these methods are still not ideal. The phenoxyacetyl

• group and linker still need nucleophilic cleavage. Palladium is expensive and difficult to remove from ODN. Photoirradiation can damage ODNs. The (p-nitrophenyl)ethyl (Npe) and (p-nitrophenyl)ethyloxycarbonyl (Npeoc) groups were also explored for sensitive ODN synthesis under non-nucleophilic conditions

Switchable selectivity in Pd-catalyzed [3 + 2] annulations of γ-oxy-2-cycloalkenones with 3-oxoglutarates: C–C/C–C vs C–C/O–C bond formation

• Yang Liu,
• Julie Oble and
• Giovanni Poli

Beilstein J. Org. Chem. 2019, 15, 1107–1115, doi:10.3762/bjoc.15.107

• -one bis-nucleophiles. Keywords: 1,4-addition; annulation; decarboxylation; palladium; Pd-catalyzed allylation reaction; Introduction The development of new strategies for the synthesis of complex carbocyclic and heterocyclic structures remains a general topic for the synthetic chemists [1]. In the

• past decades, palladium chemistry has gained an important place in the toolbox of chemists, and its use became a privileged strategy for the selective formation of carbon–carbon and carbon–heteroatom bonds [2][3][4][5]. Among the different types of palladium-catalyzed transformations, domino – alias

• addition of enol E(enol 2) followed by double decarboxylation to give the final bicyclo[4.3.0]nonane-3,8-dione (5a, steps k, l, Scheme 8, bottom line). Conclusion In conclusion, we have successfully developed two totally selective and chemodivergent methods for the palladium-catalyzed [3 + 2] annulation

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

• reaction of propiolic acid and aryl halides [78]. Furthermore, the authors have been able to carry out the reaction in a sequential manner starting from propiolic acid and aryl iodides in the presence of caesium carbonate and a palladium catalyst. Next, addition of 2-iodobenzoic acid and ammonium acetate

• , leading to final lactams 20. This mechanism is partially corroborated by the following multicomponent synthesis where benzamide 21, ortho-functionalized with a terminal alkyne group (Scheme 5), a secondary amine 22 and carbon monoxide (23) react to produce 3-methyleneisoindolinones 24 [80]. A palladium

• transformation implies initial formation of an alkynylpalladium intermediate 25 followed by carbonylation to render acylpalladium 26 (Scheme 6). Reductive substitution of palladium by amine 22 furnishes diamide derivative 27 and Pd(0), which is reoxidized to Pd(II) again by HI and oxygen. Then, intramolecular

Stereo- and regioselective hydroboration of 1-exo-methylene pyranoses: discovery of aryltriazolylmethyl C-galactopyranosides as selective galectin-1 inhibitors

• Alexander Dahlqvist,
• Axel Furevi,
• Niklas Warlin,
• Hakon Leffler and
• Ulf J. Nilsson

Beilstein J. Org. Chem. 2019, 15, 1046–1060, doi:10.3762/bjoc.15.102

• (aryltriazolyl)methyl galactopyranosyls 10a–n in fair to good yields (42–78% yields) via a copper-catalyzed Huisgen cycloaddition [17][32]. The resulting (aryltriazolyl)methyl galactopyranosyls 10a–n were debenzylated using palladium hydroxide on carbon in a 2:1 cyclohexene and ethanol mixture to give 1a–n in

• yields varying from poor to good (10–87% yields, Scheme 2). The transfer hydrogenation was selected as common hydrogenation using conditions with hydrogen gas and palladium on carbon lead to very low yields or no recovered product during the synthesis of 1a,b. Unfortunately, no arenes bearing halogen

• infrared spectroscopy, samples were pelleted with potassium bromide and analyzed on a Shimadzu FTIR-84005. 1,2-Dideoxy-1-(4-phenyl-1H-1,2,3-triazol-1-yl)-β-D-galactoheptulose (1a): Compound 10a (42 mg, 0.062 mmol) was dissolved in cyclohexene/ethanol 2:1 (1.5 mL), palladium(II) hydroxide on charcoal (17 mg

Diaminoterephthalate–α-lipoic acid conjugates with fluorinated residues

• Leon Buschbeck,
• Aleksandra Markovic,
• Gunther Wittstock and
• Jens Christoffers

Beilstein J. Org. Chem. 2019, 15, 981–991, doi:10.3762/bjoc.15.96

• trifluoromethylated benzaldehyde was accomplished as described for compound 2 and furnished product 6 in 91% yield. The Alloc-protecting group was then cleaved (95% yield of product 8) in a palladium-catalyzed allylic substitution reaction with morpholine as a scavenger of the allylic cation [45][46]. Finally, the

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

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

• the formation of a Pt-based supramolecular square took more than four weeks at 100 °C. Using a similar approach, Otera’s group also demonstrated for the formation of a bowl-shaped assembly 9 in 90% yield upon grinding for 10 min 2,4,6-tri(pyridin-3-yl)-1,3,5-triazine and palladium ((en)Pd(NO3)2

The LANCA three-component reaction to highly substituted β-ketoenamides – versatile intermediates for the synthesis of functionalized pyridine, pyrimidine, oxazole and quinoxaline derivatives

• Tilman Lechel,
• Roopender Kumar,
• Mrinal K. Bera,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2019, 15, 655–678, doi:10.3762/bjoc.15.61

• highly substituted heterocyclic compounds is possible. An intramolecular aldol-type condensation reaction efficiently furnishes pyridin-4-ols PY that can be further modified by palladium-catalyzed reactions, e.g., to specifically substituted furopyridine derivatives. Condensations of β-ketoenamides with

• alkoxyallenes, nitriles and carboxylic acids and due to the two differently protected oxygen functions of the pyridin-4-ols these intermediates could be further substituted, e.g., through palladium-catalyzed reactions, to give highly substituted pyridine derivatives in a great variety. The scope and limitations

• ]. The methoxy-substituted compound PM2 requires harsh conditions employing trimethylsilyl iodide at 80 °C to provide the intermediate hydroxy derivative PM51. In contrast, the removal of the benzyl group in PM20 can be achieved by palladium-catalyzed hydrogenolysis at room temperature to give hydroxy

Synthesis of the aglycon of scorzodihydrostilbenes B and D

• Katja Weimann and
• Manfred Braun

Beilstein J. Org. Chem. 2019, 15, 610–616, doi:10.3762/bjoc.15.56

• , the yield was lower (Scheme 2). In order to bring about the cleavage of the benzyl protecting groups in the ketones 8a and 8b by hydrogenolysis [17][18], various metal catalysts were tested. It turned out that palladium on charcoal was the only catalytic system that provided satisfying results. Ethyl

• , 69.56; H, 6.73. General procedure for the synthesis of phenols 9–11 by hydrogenolytic cleavage of benzyl ether protecting groups: An autoclave was equipped with a stirring bar and charged with O-protected dihydrostilbenes 8a,b (0.8 mmol), palladium on charcoal (50 mg) and ethyl acetate (12 mL). The

• mg, 1.5 mmol), palladium on charcoal (200 mg) in ethyl acetate (15 mL) at 3 bar hydrogen pressure for 72 h. The crude product was purified by column chromatography (silica gel; ethyl acetate/n-hexane, 1:7) to give 9 as a greenish syrup in 75% yield (356 mg); Rf 0.1; 1H NMR (CDCl3, 600 MHz) δ 2.63 (s

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

• ) catalyst was inhibited, resulting in no cycloaddition reaction occurring. To explore the synthetic practicality of this transformation, racemic compound 3b resulting from 1b and 2a was reduced using hydrogen and palladium on carbon (Scheme 2). It is interesting to note that only trans-5a was obtained and

Microwave-assisted synthesis of N,N-bis(phosphinoylmethyl)amines and N,N,N-tris(phosphinoylmethyl)amines bearing different substituents on the phosphorus atoms

• Erika Bálint,
• Anna Tripolszky,
• László Hegedűs and
• György Keglevich

Beilstein J. Org. Chem. 2019, 15, 469–473, doi:10.3762/bjoc.15.40

• carried out in the presence of a 10% palladium on carbon catalyst (Selcat Q), in methanol, at 75 °C for 3 h, and the (aminomethyl)diphenylphosphine oxide (9) was obtained in a yield of 47% after column chromatography. In the next step, (aminomethyl)phosphine oxides 5–7 were converted to bis

Convergent synthesis of the pentasaccharide repeating unit of the biofilms produced by Klebsiella pneumoniae

• Arin Gucchait,
• Angana Ghosh and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2019, 15, 431–436, doi:10.3762/bjoc.15.37

• -4,6-O-benzylidene-β-D-glucopyranoside (9). Compound 9 was treated with benzyl bromide in the presence of sodium hydride [20] to give O-benzylated derivative 10 in 90% yield in two steps, which on de-O-allylation by treatment with palladium chloride [21] furnished 2-azidoethyl 2-O-benzyl-4,6-O

• -glucopyranoside (16) in 65% yield together with some 1,2-trans glycosylated product (≈10%), which was separated by column chromatography. Compound 16 was treated with palladium chloride [21] to give the disaccharide hemiacetal derivative 17 in 75% yield, which on treatment with trichloroacetonitrile in 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

• electroluminescent devices [33]. To address these challenges, we [34] and others [35][36] have synthesized functionalized C3-symmetric molecules containing amino acids and peptides. The Negishi cross coupling [37][38] is a reliable synthetic method, which involves palladium or nickel-catalyzed coupling of organozinc

• treated with silicon tetrachloride and ethanol (SiCl4/EtOH) at room temperature for 6 h to produce the iodonated trimerized product 9 in 71% yield (Scheme 2) [45][46]. Then, the organozinc reagent 7 was coupled with triiodo derivative 9 in the presence of tetrakis(triphenylphosphane)palladium(0) (Pd(PPh3

• of Zn insertion reaction, stirring was stopped and the solid was allowed to settle down. The supernatant was carefully transferred to a suspension of triiodo derivative 9 (500 mg, 0.73 mmol) in DMF (10 mL) at room temperature. Five mol % tetrakis(triphenylphosphane)palladium (Pd(PPh3)4) was added to

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

• -shift with respect to the precursors. Dautel and Moreau have synthesized octakis[2-(p-carboxyphenyl)ethyl] (Scheme 7) and octakis[2-(4-carboxy-1,1’-biphenyl)ethyl]silsesquioxane via cross-metathesis methodology [17]. In the presence of palladium and dihydrogen the synthesized derivatives undergo, under

A novel and efficient synthesis of phenanthrene derivatives via palladium/norbornadiene-catalyzed domino one-pot reaction

• Yue Zhong,
• Wen-Yu Wu,
• Shao-Peng Yu,
• Tian-Yuan Fan,
• Hai-Tao Yu,
• Nian-Guang Li,
• Zhi-Hao Shi,
• Yu-Ping Tang and
• Jin-Ao Duan

Beilstein J. Org. Chem. 2019, 15, 291–298, doi:10.3762/bjoc.15.26

• palladium-catalyzed reaction that results in phenanthrene derivatives using aryl iodides, ortho-bromobenzoyl chlorides and norbornadiene in one pot. This dramatic transformation undergoes ortho-C–H activation, decarbonylation and subsequent a retro-Diels–Alder process. Pleasantly, this protocol has a wider

• substrate range, shorter reaction times and higher yields of products than previously reported methods. Keywords: C–H activation; norbornadiene; palladium; phenanthrene derivatives; Introduction Phenanthrene is a polycyclic aromatic hydrocarbon which contains three benzene rings. The phenanthrenes can be

• functional groups. Subsequently, facile one-pot approaches had been realized via norbornene-mediated palladium-catalyzed Catellani reaction by Lautens’ group [10] (Scheme 1c). Though this strategy was superior to previous methods in terms of mildness of the reaction conditions, it had a limited substrate

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

• strategy based on an Evans’ aldol reaction. Mildly oxidizing conditions using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) were used for the removal of the p-methoxybenzyl (PMB) group to provide alcohols 14 (Scheme 3). Several palladium(II) catalysts have been tested for the conversion of alcohols to

Generation of 1,2-oxathiolium ions from (arysulfonyl)- and (arylsulfinyl)allenes in Brønsted acids. NMR and DFT study of these cations and their reactions

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov,
• Olesya V. Khoroshilova and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2018, 14, 2897–2906, doi:10.3762/bjoc.14.268

• noting, that compounds 3a–h have strictly cis-configuration of SO2Ar group and a vinyl substituent at C2 carbon. It should be mentioned that palladium-catalyzed isomerization of such (arylsulfonyl)allenes 2 into trans-butadienes 3 was described recently [23]. Herein, we have developed a novel metal-free

Unnatural α-amino ethyl esters from diethyl malonate or ethyl β-bromo-α-hydroxyiminocarboxylate

• Eloi P. Coutant,
• Vincent Hervin,
• Glwadys Gagnot,
• Candice Ford,
• Racha Baatallah and
• Yves L. Janin

Beilstein J. Org. Chem. 2018, 14, 2853–2860, doi:10.3762/bjoc.14.264

• the water formed in situ. The 1H NMR monitoring of crude samples pointed out a complete conversion, most often overnight at 60 °C, and the resulting solutions of alkylidenemalonates 6a–al were then directly reduced to give the malonates 3a–al. For this reduction step, palladium-based catalytic

• 2ae. First of all, reduction of the alkylidenemalonate 6ae using a palladium-based catalytic hydrogenation also led to the concomitant hydrogenation of the furan ring to give compound 8. As depicted, this actually allowed us to prepare to the 2-tetrahydrofuranyl-bearing α-aminoester 10 in a 35

• derivative 29. Indeed, coupling these compounds with cyclopropylboronic acid gave the corresponding cyclopropyl derivatives 14, 18 or 30 in 60, 47 and 75% yield, respectively. The palladium-based reduction of compound 14 and 18 also led to the hydrogenation of their cyclopropyl ring into a propyl side chain

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

• acrylates 2n or 2o using sodium borohydride, the α-nitro esters 6n and 6o were isolated in the rather modest yields indicated in Table 1. We then focused on the model reduction of acrylate 2n into 6n. Since all our attempts to achieve a palladium-catalyzed hydrogenation failed, we tried other borohydride

• acid in ethanol overnight gave a sufficient amount of the (pure) target phenyl-bearing α-amino ester 10 which had been previously obtained by catalytic hydrogenation using palladium [20]. The same transformation sequences were used starting with compound 6n and provided the furan-bearing α-amino ester

• [21] between two equivalents of ethyl nitroacetate (4) and styrene (15), gave the isoxazoline 16 in a 72% yield as a latent α-amino ester [22][23][24]. From this compound, a reductive cleavage of the isoxazoline ring was initiated using palladium over charcoal and a large excess of ammonium formate in

Synthesis and biological evaluation of 1,2-disubstituted 4-quinolone analogues of Pseudonocardia sp. natural products

• Stephen M. Geddis,
• Teodora Coroama,
• Suzanne Forrest,
• James T. Hodgkinson,
• Martin Welch and
• David R. Spring

Beilstein J. Org. Chem. 2018, 14, 2680–2688, doi:10.3762/bjoc.14.245

• products 5 and 6 proved satisfactory in most cases, some optimisation was required for substrates possessing unsaturated functionality attached to the amine (Table 1). When the palladium-catalysed conditions were employed [20], a complex mixture resulted, from which no product could be obtained (Table 1

• of primary amines 12a–f with ynones 11a and 11b. aFollowing concentration in vacuo, further purification using silica gel flash chromatography was required. Cyclisation of precursors 13 to natural product analogues 14 using palladium- or copper-catalysed conditions. Yields quoted are isolated. a13ab

Novel solid-phase strategy for the synthesis of ligand-targeted fluorescent-labelled chelating peptide conjugates as a theranostic tool for cancer

• Sagnik Sengupta,
• Mena Asha Krishnan,
• Premansh Dudhe,
• Ramesh B. Reddy,
• Bishnubasu Giri,
• Sudeshna Chattopadhyay and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2018, 14, 2665–2679, doi:10.3762/bjoc.14.244

• synthetic strategy. Usually, the allyl protecting group in N-Fmoc-Lys(Alloc)-OH is deprotected using Pd(PPh3)4 catalyst. However, the sulfur atom present in the cysteine moiety of the chelating core is known to poison palladium catalysts resulting in complete failure of the deprotection of the ε-amino allyl

• protecting moiety. Moreover, palladium is a heavy metal and traceless removal of it from the resulting bioconjugates 13 and 17 is near to impossible. Since the prepared bioconjugates 13 and 17 are to be utilized for imaging of human cancer cell lines, presence of any heavy metals in the synthetic strategy

The design and synthesis of an antibacterial phenothiazine–siderophore conjugate

• Abed Tarapdar,
• James K. S. Norris,
• Oliver Sampson,
• Galina Mukamolova and
• James T. Hodgkinson

Beilstein J. Org. Chem. 2018, 14, 2646–2650, doi:10.3762/bjoc.14.242

• azotochelin. Catechol-based siderophores can act as xenosiderophores and be recognised for uptake by Gram-negative bacteria and mycobacteria [14][15]. Most commonly benzyl protecting groups are used in the synthesis of catechol siderophores and cleaved in the final step by palladium catalysed hydrogenation

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

• (−)-aspidophytine (5) differs from 1-acetylaspidoalbidine (4) only in the degree of unsaturation and the substitution pattern on the aromatic ring (Figure 1). The design of propellanes demands unique synthetic methods and these include: manganese or palladium-catalyzed transformations [10], the Diels–Alder (DA

Synthesis of aryl sulfides via radical–radical cross coupling of electron-rich arenes using visible light photoredox catalysis

• Amrita Das,
• Mitasree Maity,
• Simon Malcherek,
• Burkhard König and
• Julia Rehbein

Beilstein J. Org. Chem. 2018, 14, 2520–2528, doi:10.3762/bjoc.14.228

• triflates [8], and diazonium salts [9]. Typical metals used are palladium [10][11][12][13], copper [14][15][16][17][18][19][20][21], nickel [22][23][24], iron [25][26][27][28][29], cobalt [30][31][32], and rhodium [33][34]. Aryl sulfides are also synthesized by cross coupling of thiols and aryl Grignard

Synergistic approach to polycycles through Suzuki–Miyaura cross coupling and metathesis as key steps

• Sambasivarao Kotha,
• Milind Meshram and
• Chandravathi Chakkapalli

Beilstein J. Org. Chem. 2018, 14, 2468–2481, doi:10.3762/bjoc.14.223

• reaction occurs under mild reaction conditions. Among different metathetic processes, ring-closing metathesis (RCM) [1][2][3][4][5][6] is of a greater interest than cross-metathesis (CM). It is a widely used protocol for the synthesis of unsaturated cyclic systems [7]. Palladium-catalyzed Suzuki–Miyaura

• useful protocol to build indene derivatives by employing SM coupling and RCM in sequence. To this end, the SM coupling of triflate 7 was accomplished by using pinacol boronic ester 8 in the presence of a palladium catalyst to give the cross-coupling product 9 (75%). Later on, exposure of the diolefinic

• -workers [33] demonstrated an efficient route for the construction of the benz[a]anthracene structural unit by employing SM cross coupling followed by RCM sequence. Treatment of the bromonaphthalene derivative 20 with (2-formyl-4-methoxyphenyl)boronic acid (21) in the presence of a palladium catalyst