Photocatalyzed syntheses of phenanthrenes and their aza-analogues. A review

• Alessandra Del Tito,
• Havall Othman Abdulla,
• Davide Ravelli,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 1476–1488, doi:10.3762/bjoc.16.123

• Pd(OAc)2 (5 mol %), was involved in the design of an efficient annulation between benzamides and in situ-generated arynes. The process occurred under oxygen saturated atmosphere at room temperature, likewise offering a straightforward access to the phenanthridone backbone [93]. Conclusion

In silico rationalisation of selectivity and reactivity in Pd-catalysed C–H activation reactions

• Liwei Cao,
• Mikhail Kabeshov,
• Steven V. Ley and
• Alexei A. Lapkin

Beilstein J. Org. Chem. 2020, 16, 1465–1475, doi:10.3762/bjoc.16.122

• the two mechanisms of Pd-catalysed C–H activation reaction considered in this study. Comparison of the published experimental results with the computational predictions for the Pd(OAc)2-catalysed reactions.a Predicting C–H activation bond for heteroaromatic compounds.a A comparison of the published

• experimental results with the computational predictions for the Pd(OAc)2-catalysed reactions.a A mechanism threshold tested based on the literature examples.a Supporting Information Supporting Information File 96: Comutational details, comparison of data, mechanistic threshold, Cartesian coordinates and

The McKenna reaction – avoiding side reactions in phosphonate deprotection

• Katarzyna Justyna,
• Joanna Małolepsza,
• Damian Kusy,
• Waldemar Maniukiewicz and
• Katarzyna M. Błażewska

Beilstein J. Org. Chem. 2020, 16, 1436–1446, doi:10.3762/bjoc.16.119

• . Since the known procedures for the syntheses of oxazoles are rather harsh and usually involve higher temperature [Pd(OAc)2, toluene, AcOH, 100 °C, 24 h [41] and/or the presence of Lewis acids (FeCl3, ACN (24 h, 80 °C) or 1,2-DCE (2 h, 80 °C), DCM (24 h, 45 °C) [40]], we envisioned that the present

Synthesis of pyrrolidinedione-fused hexahydropyrrolo[2,1-a]isoquinolines via three-component [3 + 2] cycloaddition followed by one-pot N-allylation and intramolecular Heck reactions

• Xiaoming Ma,
• Suzhi Meng,
• Xiaofeng Zhang,
• Qiang Zhang,
• Shenghu Yan,
• Yue Zhang and
• Wei Zhang

Beilstein J. Org. Chem. 2020, 16, 1225–1233, doi:10.3762/bjoc.16.106

• using 10 mol % of Pd(OAc)2 or 10 mol % of PdCl2 with 20 mol % of PPh3 as a ligand and 2 equiv of K2CO3 in MeCN at 80 °C for 10 h without additive to give 6-exo-cyclized product 9a in 32% and 18% yields, respectively (Table 1, entries 1 and 2). Addition of NaOAc increased the yield of 9a to 71% (Table 1

• the amount of Pd(OAc)2 to 5 mol % or the reaction temperature to 40 °C gave lower product yields (Table 1, entries 8 and 10). Double the amount of Pd(OAc)2 to 20 mol% gave 9a in 79% yield, just 1% increase than that of using 10 mol % of catalyst (Table 1, entry 9). Besides K2CO3, other bases including

• Na2CO3, Cs2CO3 and Et3N were also used for the Heck reaction, but none of them improved the product yield (Table 1, entries 12–14). A base-free control reaction gave 9a in 10% yield (Table 1, entry 15). Thus, the optimized conditions for the Heck reaction was to use 10 mol % of Pd(OAc)2, 20 mol % of PPh3

Synthesis of esters of diaminotruxillic bis-amino acids by Pd-mediated photocycloaddition of analogs of the Kaede protein chromophore

• Esteban P. Urriolabeitia,
• Pablo Sánchez,
• Alexandra Pop,
• Cristian Silvestru,
• Eduardo Laga,
• Ana I. Jiménez and
• Carlos Cativiela

Beilstein J. Org. Chem. 2020, 16, 1111–1123, doi:10.3762/bjoc.16.98

• reaction of 4-((Z)-arylidene)-2-(E)-styryl-5(4H)-oxazolones 2 with Pd(OAc)2 resulted in ortho-palladation and the formation of a dinuclear open-book complexes 3 with carboxylate bridges, where the Pd atom is C^N bonded to the oxazolone. In 3 the two exocyclic C=C bonds of the oxazolone are in a face-to

• oxazolones 2 promoted by Pd(OAc)2, which shows multiple possibilities (Figure 2b). Treatment of the oxazolones 2a–j with Pd(OAc)2 (1:1 molar ratio) in CF3CO2H as solvent under reflux for 2 h resulted in the formation of the dinuclear complexes 3a–f and 3h–j, as shown in Scheme 1. In the case of oxazolone 2g

• . The new (Z)-4-arylidene-2-(E)-styryl-5(4H)-oxazolones 2 react with Pd(OAc)2 through a C–H bond activation reaction to give the dinuclear ‘open-book’ ortho-palladated complexes [Pd2(μ-O2CCF3)2(C^N-oxa))2] 3 with bridging carboxylate ligands. Despite the presence in 2 of different functional groups and

Palladium-catalyzed regio- and stereoselective synthesis of aryl and 3-indolyl-substituted 4-methylene-3,4-dihydroisoquinolin-1(2H)-ones

• Valeria Nori,
• Antonio Arcadi,
• Armando Carlone,
• Fabio Marinelli and
• Marco Chiarini

Beilstein J. Org. Chem. 2020, 16, 1084–1091, doi:10.3762/bjoc.16.95

• catalytic system showed that the ligand-free PdCl2 was the most effective catalyst (Table 1, entry 14). Other catalysts such as Pd(PPh3)4, Pd/C or Pd(OAc)2 provided inferior results (Table 1, entries 11–13). We then examined the reaction of 2a with 1.5 equiv of a variety of arylboronic acids. Using the

Fluorinated phenylalanines: synthesis and pharmaceutical applications

• Laila F. Awad and
• Mohammed Salah Ayoup

Beilstein J. Org. Chem. 2020, 16, 1022–1050, doi:10.3762/bjoc.16.91

• presence of Pd(OAc)2 as a catalyst. The corresponding β-fluoro derivatives 159a–v were obtained with high stereoselectivity using DCM and iPrCN as co-solvent (30:1 v/v). Interestingly reducing the Pd(OAc)2 concentration from 10 mol % to 6 mol % led to an improved yield of 73% for 159a, 159g, and 159t

Synthesis and properties of tetrathiafulvalenes bearing 6-aryl-1,4-dithiafulvenes

• Aya Yoshimura,
• Hitoshi Kimura,
• Kohei Kagawa,
• Mayuka Yoshioka,
• Toshiki Itou,
• Dhananjayan Vasu,
• Takashi Shirahata,
• Hideki Yorimitsu and
• Yohji Misaki

Beilstein J. Org. Chem. 2020, 16, 974–981, doi:10.3762/bjoc.16.86

• Abstract Novel multistage redox tetrathiafulvalenes (TTFs) bearing 6-aryl-1,4-dithiafulvene moieties were synthesized by palladium-catalyzed direct C–H arylation. In the presence of a catalytic amount of Pd(OAc)2, P(t-Bu3)·HBF4, and an excess of Cs2CO3, the C–H arylation of TTF with several aryl bromides

Bipyrrole boomerangs via Pd-mediated tandem cyclization–oxygenation. Controlling reaction selectivity and electronic properties

• Liliia Moshniaha,
• Marika Żyła-Karwowska,
• Joanna Cybińska,
• Piotr J. Chmielewski,
• Ludovic Favereau and
• Marcin Stępień

Beilstein J. Org. Chem. 2020, 16, 895–903, doi:10.3762/bjoc.16.81

• that the coupling and α-oxygenation can also be achieved with 1 equiv of Pd(OAc)2 in the presence of 2 equiv of silver carbonate. Nevertheless, Ag2CO3 oxidation provided lower yields and the efficiency of this variant was dramatically diminished when the loading of palladium(II) acetate was decreased

• in toluene, dichloromethane and acetonitrile. The previously reported family of the boomerang bipyrroles obtained by Pd-induced double C–H bond activation [32]. Synthesis and structures of α-free and α-oxygenated bipyrrole boomerangs. Reagents and conditions: (a) 30 mM in AcOH, 3 equiv Pd(OAc)2, 6

• equiv KOAc, 120 °C, 1 h; (b) 3 mM in AcOH, 3 equiv Pd(OAc)2, 120 °C, 1 h. Isolated yields are given for each set of conditions. M enantiomers are depicted for cNDA3O, cNMI3O, cNMI3H. n.d. = not determined. Screening of reaction conditions.a Experimental and calculateda properties of fused bipyrroles

Rhodium-catalyzed reductive carbonylation of aryl iodides to arylaldehydes with syngas

• Zhenghui Liu,
• Peng Wang,
• Zhenzhong Yan,
• Suqing Chen,
• Dongkun Yu,
• Xinhui Zhao and
• Tiancheng Mu

Beilstein J. Org. Chem. 2020, 16, 645–656, doi:10.3762/bjoc.16.61

• halogens to arylaldehydes have been developed. The homogeneous systems included Pd(OAc)2 with propyl di-tert-butylphosphinite ligand [30], Pd(acac)2 with dppm ligand [31], Pd(OAc)2 with CataCXium A ligand [32], and all of the three systems employed TMEDA as the base and toluene as the solvent. The

A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions

• Pezhman Shiri and
• Jasem Aboonajmi

Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52

• 100 °C for one day, cooled, and filtered. The material Pd–Cu@rGO (78), as heterogeneous nanocatalyst, was prepared by anchoring Pd(OAc)2 on Cu@rGO in toluene via pyrolysis. The catalyst was highly active in one-pot condensations of alkyl/aryl-substituted triazole heterocycles with cycloadditions and

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• oxidants [151][152][153]. To overcome these drawbacks, recently, Cho’s group synthesized carbazole derivatives using a dual photoredox-catalyzed intramolecular C−H bond amination of N-substituted 2-amidobiaryls with photoredox catalyst 14 in presence of Pd(OAc)2 as a cocatalyst under aerobic conditions

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

• -withdrawing groups, using Pd(OAc)2 as catalyst and Cu(OAc)2 as oxidant [25]. Since then, several variants of the reaction involving Pd catalysis and various oxidants have been reported for the synthesis of 3-alkenylindoles. For example, Chen et al. and Huang et al. independently reported the C3 alkenylation

• of indoles using Pd(OAc)2 and Pd(II)/polyoxometallate, respectively, as a catalyst and molecular oxygen as the oxidant [26][27]. Verma and co-workers used the reaction between indoles and alkenes in the presence of a Pd(OAc)2 catalyst, a Cu(OAc)2 oxidant, and a 2-(1-benzotriazolyl)pyridine ligand [28

• ]. Noël and co-workers reported the C3–H olefination of indoles using Pd(OAc)2 as a catalyst and molecular oxygen as the oxidant under continuous flow conditions [29]. Jia et al. reported the synthesis of 3-alkenylindoles using Pd(OAc)2 as the catalyst and MnO2 as the oxidant under ball milling conditions

Starazo triple switches – synthesis of unsymmetrical 1,3,5-tris(arylazo)benzenes

• Andreas H. Heindl and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2020, 16, 22–31, doi:10.3762/bjoc.16.4

• with a 1.61 M solution of P(t-Bu)3 (395 µL, 636 µmol, 15 mol %) in dry toluene. All following operations were carried out in a fume hood under Schlenk conditions. tert-Butyl 1-(4-cyanophenyl)hydrazine-1-carboxylate (1.00 g, 4.25 mmol, 1.00 equiv), 15 (1.82 g, 4.24 mmol, 1.00 equiv), Pd(OAc)2 (144 mg

• carried out in a fume hood under Schlenk conditions. Compound 15 (1.80 g, 4.19 mmol, 1.00 equiv), tert-butyl 1-(4-methoxyphenyl)hydrazine-1-carboxylate (1.04 g, 4.36 mmol, 1.04 equiv), Pd(OAc)2 (145 mg, 633 µmol, 15.1 mol %), and Cs2CO3 (2.07 g, 6.29 mmol, 1.5 equiv) were added and suspended in dry

• conditions. To the Schlenk tube, 16a (100 mg, 172 µmol, 1.00 equiv), N-Boc-N-phenylhydrazine (110 mg, 528 µmol, 3.08 equiv), Pd(OAc)2 (2 mg, 9 µmol, 5 mol %), and Cs2CO3 (170 mg, 522 µmol, 3.04 equiv) were added. After the addition of dry toluene (1.7 mL), the mixture was stirred at rt for 30 min. Then, the

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

• compounds 1 and 2, was successfully achieved. We used tri(o-tolyl)phosphine (P(o-tol)3, palladium(II) acetate (Pd(OAc)2) and obtained the desired product (E)-benzyl 3-(6-aminopyridin-3-yl)acrylate in 86% yield (see Supporting Informaiton File 1). However, when the same conditions were applied to alkyl 3-(6

• the reaction temperature to 110 °C and prolonged the time to 50 min (Table 1, entry 3) and obtained product 3 with 58% yield. Then, we reduced the loading of the ligand, P(o-tol)3 and catalyst Pd(OAc)2, to one fourth of the loading used in the previous experiment which improved the yield of the

• ), or even complete lack of conversion as in the case of tricyclohexylphosphine (P(Cy)3 (Table 1, entries 8–10). Also no reaction was observed in the absence of Pd(OAc)2 and P(o-tol)3, while partial conversion into product 3 occurred in the presence of Pd(OAc)2 (Table 1, entries 11 and 12). In addition

Palladium-catalyzed Sonogashira coupling reactions in γ-valerolactone-based ionic liquids

• László Orha,
• József M. Tukacs,
• László Kollár and
• László T. Mika

Beilstein J. Org. Chem. 2019, 15, 2907–2913, doi:10.3762/bjoc.15.284

• that while Pd(PPh3)4, palladium acetate (Pd(OAc)2), PdCl2(PPh3)2, and tris(dibenzylideneacetone)dipalladium (Pd2(DBA)3) all catalyzed the Sonogashira reaction, the PdCl2(PPh3)2 precursor turned out to have the best activity in the light of reaction rates (Figure 1). In the presence of 0.5 mol % of

Palladium-catalyzed synthesis and nucleotide pyrophosphatase inhibition of benzo[4,5]furo[3,2-b]indoles

• Hoang Huy Do,
• Saif Ullah,
• Alexander Villinger,
• Joanna Lecka,
• Jean Sévigny,
• Peter Ehlers,
• Jamshed Iqbal and
• Peter Langer

Beilstein J. Org. Chem. 2019, 15, 2830–2839, doi:10.3762/bjoc.15.276

• ). As compared to Pd2(dba)3, the use of Pd(OAc)2 as the Pd source resulted in a decrease of the yield (52%). Performing the reaction in dioxane or DMF gave lower yields as well. In summary, up to 75% yield of 5b could be achieved using BINAP and Pd2(dba)3 as the catalytic system. Subsequently, the scope

In search of visible-light photoresponsive peptide nucleic acids (PNAs) for reversible control of DNA hybridization

• Lei Zhang,
• Greta Linden and
• Olalla Vázquez

Beilstein J. Org. Chem. 2019, 15, 2500–2508, doi:10.3762/bjoc.15.243

• )aminoethyl]glycine residue –Aeg(Alloc)– was selectively deprotected in the presence of Pd(OAc)2, Ph3P, NMM, PhSiH3 in CH2Cl2 for 2 h. Subsequently, carboxy photoswitches were introduced using Oxyma and N,N’-diisopropylcarbodiimide (DIC) as coupling agent. We explored two different types of photoswitches

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors

• Christoph W. Grathwol,
• Nathalie Wössner,
• Sören Swyter,
• Adam C. Smith,
• Enrico Tapavicza,
• Robert K. Hofstetter,
• Anja Bodtke,
• Manfred Jung and
• Andreas Link

Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214

• ) appropriate boronic acid, Pd(PPh3)4, Na2CO3, DMF, H2O, microwave, 15 min, 150 °C, 43–64%. Reagents and conditions: a) Pd2(dba)3 or Pd(OAc)2, P(o-tol)3, TEA, DMF, 120–140 °C, 0.7–24 h, 11–75%; b) potassium vinyltrifluoroborate, Cs2CO3, PdCl2(PPh3)2, ACN, H2O, 1.5 h, 120 °C, 78% c) tributylvinyltin, Pd(PPh3)4

Regioselective Pd-catalyzed direct C1- and C2-arylations of lilolidine for the access to 5,6-dihydropyrrolo[3,2,1-ij]quinoline derivatives

• Hai-Yun Huang,
• Haoran Li,
• Thierry Roisnel,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2019, 15, 2069–2075, doi:10.3762/bjoc.15.204

• heteroaromatics [38], we initially employed 1 mol % Pd(OAc)2 catalyst associated to KOAc as the base in DMA at 150 °C as the reaction conditions to promote the coupling of lilolidine with 3-bromobenzonitrile (Table 1, entry 1). Under these conditions a mixture of the α- and β-arylated lilolidines 1a and 1b was

• obtained in a 64:36 ratio. Then, the influence of some bases on the regioselectivity with Pd(OAc)2 catalyst was examined. With CsOAc a similar regioselectivity than with KOAc was obtained, whereas the use of NaOAc afforded the products 1a and 1b in an 85:15 ratio, but with a moderate conversion of 3

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

• for efficient syntheses of IPs [20]. In recent years much attention has been paid towards the exploration of transition metals (TMs) as homogeneous as well as heterogeneous catalytic system like Pd(OAc)2 [21], CuI [22], ZnO [23], ZnI2 [24], Cu(OTf)2 [25], Sc(OTf)3 [26], RuCl3 [27], [Cp*RhCl2]2 (Cp

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

• for [3 + 2] C–C/N–C bond-forming annulation [31], the first tests were performed with the following two catalytic systems: [Pd(η3-C3H5)Cl]2 (5 mol %), dppf (15 mol %)], and [Pd(OAc)2 (10 mol %), dppb (15 mol %)] in THF at room temperature (Table 1, entries 1 and 2). These conditions promptly (ca. 1

• hour) generated annulated product 4a arising from C-allylation (C–C bond forming)/intramolecular O-Michael addition (O–C bond forming) sequence. The purification of the crude reaction was easier using the Pd(OAc)2 and dppb system (Table 1, entry 2), which was thus chosen to continue the optimization

• ). The above work allowed obtaining the optimal reaction conditions for the generation of the furocycloalkanone 4a [Pd(OAc)2 (10 mol %), dppb (15 mol %) in DMSO, 1 h at rt (conditions A)] as well as for the formation of the bicyclo[4.3.0]nonane-3,8-dione (5a) [Pd(OAc)2 (10 mol %), dppb (15 mol %) in DMSO

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

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

• azobenzene [58]. The cyclopalladation process was proved to be a highly regioselective process and the observed palladation rate was faster compared to the conventional solution-phase method. An equimolar amount of 4'-(N,N-dimethylamino)-4-nitroazobenzene and Pd(OAc)2 in the presence of 25 μL of glacial

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

• (PPh3)4/PPh3 as the catalyst, Cs2CO3 as base, and dimethyl formamide (DMF) as solvent at 105 °C for 10 h under N2 atmosphere. Meanwhile, different pallladium species were tested in this reaction system. It was found that Pd(OAc)2 was the most effective palladium catalyst, and the desired product y-1 was

• (1a, 3.0 mmol, 1.0 equiv, 0.654 g), 2-bromo-4,5-dimethoxybenzoyl chloride (3.6 mmol, 1.2 equiv, 1.006 g), and norbornadiene (6.0 mmol, 2.0 equiv, 0.553 g) was performed in the presence of 0.15 mmol of Pd(OAc)2, 0.375 mmol of PPh3 and 6.75 mmol of Cs2CO3 at 105 °C in DMF under N2 for 30 h, the desired

• with aryl iodide (0.30 mmol, 1.0 equiv), ortho-bromobenzoyl chlorides (0.36 mmol, 1.2 equiv), norbornadiene (0.60 mmol, 2.0 equiv), Pd(OAc)2 (5 mol %), triphenylphosphine (12.5 mol %), Cs2CO3 (0.675 mmol, 2.25 equiv), and DMF (4 mL). The mixture was stirred at 105 °C under nitrogen atmosphere for 10 h