Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

• Jannis Ludwig,
• Julian Helberg,
• Hendrik Zipse and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2119–2126, doi:10.3762/bjoc.16.179

• Abstract We present the synthesis and the photochemical and catalytic switching properties of an azopyridine as a photoswitchable ligand, covalently attached to a Ni(II)-porphyrin. Upon irradiation with 530 nm (green light), the azopyridine switches to the cis configuration and coordinates with the Ni2

• + ion. Light of 435 nm (violet) isomerizes the ligand back to the trans configuration, which decoordinates for steric reasons. This so-called record player design has been used previously to switch the spin state of Ni2+ between singlet and triplet. We now use the coordination/decoordination process to

• -epoxypropane to propylene carbonate using an aluminum porphyrin and a photoresponsive ligand. The catalytic activity of the metal porphyrin depended on the axial coordination of an azostilbene and coordination of the latter ligand was controlled by photoisomerization of the stilbene unit [9]. Hecht et al

Efficient [(NHC)Au(NTf₂)]-catalyzed hydrohydrazidation of terminal and internal alkynes

• Maximillian Heidrich and
• Herbert Plenio

Beilstein J. Org. Chem. 2020, 16, 2080–2086, doi:10.3762/bjoc.16.175

• alkynes (7a–j, 10 examples, 0.2–0.5 mol % [(NHC)Au(NTf2)], T = 60–80 °C) utilizing a complex with a sterically demanding bispentiptycenyl-substituted NHC ligand and the benign reaction solvent anisole, is reported. Keywords: alkyne; gold; homogeneous catalysis; hydrohydrazidation; NHC ligand

• = 60 °C, solvent chlorobenzene, reaction time 24 h, catalyst loading 0.2 mol %). The following conversions were observed: complex 1 >99%, complex 2 16%, complex 3 38%, complex 4 31%, and complex 5 60%. Complex 1 having a bispentiptycene-NHC ligand was the clear best among the five NHC-gold complexes

Syntheses of spliceostatins and thailanstatins: a review

• William A. Donaldson

Beilstein J. Org. Chem. 2020, 16, 1991–2006, doi:10.3762/bjoc.16.166

• the (R,R)-ProPhenol ligand [16] to accomplish a catalytic asymmetric addition of methyl propynoate to acetaldehyde to give 18 in high enantiopurity (98% ee). Jacobsen’s group [17][18] utilized the Noyori Ru-catalyzed transfer hydrogenation [19] of the 3-butyne-2-one 19, which gave 20 with 97% ee. The

Synergy between supported ionic liquid-like phases and immobilized palladium N-heterocyclic carbene–phosphine complexes for the Negishi reaction under flow conditions

• Edgar Peris,
• Raúl Porcar,
• María Macia,
• Jesús Alcázar,
• Eduardo García-Verdugo and
• Santiago V. Luis

Beilstein J. Org. Chem. 2020, 16, 1924–1935, doi:10.3762/bjoc.16.159

• modulated through systematic variations of the steric and electronic design vectors of the NHC ligand [2]. These complexes have been used as highly efficient catalysts for a wide variety of C–C and C–X cross-coupling reactions [3]. Among others, different NHC–Pd complexes have been designed as efficient

• this leaching process, the role of the ligand and the support on the evolution of the catalytic systems should be carefully considered. It has been shown that the immobilization of Pd-catalysts or precatalysts onto supported ionic liquid-like materials can facilitate the recapture by the support of the

• corresponding Pd–NHC complexes 4a and 4b (Scheme 1) were obtained by treatment of the supported imidazolium species with Pd(OAc)2 in the presence of a base. The amount of immobilized NHC ligand was determined by elemental analysis, while the palladium loaded on the polymer was determined by ICP analyses (see

On the hydrolysis of diethyl 2-(perfluorophenyl)malonate

• Ilya V. Taydakov and
• Mikhail A. Kiskin

Beilstein J. Org. Chem. 2020, 16, 1863–1868, doi:10.3762/bjoc.16.153

• range by fluorination (directly or indirectly) of initial organic molecules. In the ongoing project, we are interested in synthesizing 2-(perfluorophenyl)malonic acid (2, Figure 1) as a new ligand for the preparation of 3d and 4f heterometallic coordination compounds. Results and Discussion To our

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• as sole oxidant and implementing two photoredox cycles is presented in Figure 16. After a ligand exchange, Co(II) undergoes a single-electron transfer (SET) oxidation to Co(III) with a concomitant formation of the reduced organic photocatalyst. The thus generated highly reactive Co(III) complex

• expected products in good to excellent yields (Figure 37 and Figure 38). The addition of diphenylphosphoric acid as a ligand guaranteed higher yields and a broader reaction scope [100], including C–H activation substrates bearing alternative and modifiable DGs such as pyrazoles or oxazolines, as well as

• an oxidative ortho-C–H addition step via a metal-to-ligand charge transfer process, delivering the Rh(III) hydride species. Following borylation of the Rh(III) intermediate and subsequent reductive elimination liberate the expected coupling product with concomitant regeneration of the catalytically

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• extrusion of two carbon monoxide ligands from the starting cobalt species, allowing the alkyne group to bind to the cobalt metal centers. The subsequent coordination of the olefin counterpart requires the extrusion of a third carbon monoxide ligand, leading to pentacarbonyl complex II. This highly

• stereochemical outcome of the overall process. A carbon monoxide ligand then undergoes migratory insertion into one of the Co–C bonds in cobaltacycle V, followed by reductive elimination to release the final product (Scheme 3). As mentioned above, the regiochemistry of this transformation is, in most cases

Fluorohydration of alkynes via I(I)/I(III) catalysis

• Jessica Neufeld,
• Constantin G. Daniliuc and
• Ryan Gilmour

Beilstein J. Org. Chem. 2020, 16, 1627–1635, doi:10.3762/bjoc.16.135

• Lewis base upon ligand exchange (Figure 5) [56]. This working hypothesis may also rationalise the deletion experiment (10), the recalcitrance of acetyl derivatives, and the striking reactivity disparity between amides (12/13) and the phthalimide derivative 16. Finally, to investigate the fate of water

A dynamic combinatorial library for biomimetic recognition of dipeptides in water

• Florian Klepel and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2020, 16, 1588–1595, doi:10.3762/bjoc.16.131

• developed a DCL composed of Cu2+, Ni2+ complexes. The addition of dipeptides caused characteristic spectral changes by ligand-exchange reactions [18]. We previously used a peptide derived DCL for the development of artificial carbohydrate receptors [19][20]. An intriguing example derived from that work is

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• spectrum through direct VB/adsorbate electron transfer transitions [93][94]. HPCats modified with coordinating transition metal complexes also usually display significant changes to their absorption spectrum through the introduction of metal-to-ligand, ligand-to-metal, ligand-to-ligand, and metal-to-metal

• (type I excitation). The direct VB-to-LUMO or VB-to-ligand transition is also enabled and produces a hypsochromic shift in the HPCat absorption spectrum. An excellent review of coordination chemistry controlled design of heterogeneous photocatalysis has been published by Xiong and co-workers, and we

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

• , explaining the experimental observations for C–H activation reactions, depending on the nature of a ligand (Ln) and transition metal (M) in the catalytically active species (LnM). These mechanisms include four elementary steps: oxidative addition, σ-bond metathesis, electrophilic substitution and 1,2

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

Synthesis, antiinflammatory activity, and molecular docking studies of bisphosphonic esters as potential MMP-8 and MMP-9 inhibitors

• Abimelek Cortes-Pacheco,
• María Adelina Jiménez-Arellanes,
• Francisco José Palacios-Can,
• José Antonio Valcarcel-Gamiño,
• Rodrigo Said Razo-Hernández,
• María del Carmen Juárez-Vázquez,
• Adolfo López-Torres and
• Oscar Abelardo Ramírez-Marroquín

Beilstein J. Org. Chem. 2020, 16, 1277–1287, doi:10.3762/bjoc.16.108

• ligand efficiency (LE) of each bisphosphonate is shown; the ligand efficiency stands for the coefficient of the interaction energy by the number of atoms in the molecule (excluding hydrogen atoms). By the inspection of the results above, there is a correlation between the LE parameter in MMP-8 and the

• was pointing away from the zinc ion [39]. The calculated distances from the Zn2+ ion and the different sites at the ligand and the protein are summarized in Table 5. The zinc chelation in MMP-9 occurred in a different way. The predicted orientation of the histidine residues at the catalytic site were

• molecules inside the catalytic site allowed the coordination through the ester groups rather than through the phosphonate moieties. The calculated distances from the Zn2+ ion and the different sites at the ligand and the protein are summarized in Table 6. In Figure 4, a schematic representation of the

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

Activated carbon as catalyst support: precursors, preparation, modification and characterization

• Melanie Iwanow,
• Tobias Gärtner,
• Volker Sieber and
• Burkhard König

Beilstein J. Org. Chem. 2020, 16, 1188–1202, doi:10.3762/bjoc.16.104

A smart deoxyribozyme-based fluorescent sensor for in vitro detection of androgen receptor mRNA

• Ekaterina A. Bryushkova,
• Erik R. Gandalipov and
• Julia V. Nuzhina

Beilstein J. Org. Chem. 2020, 16, 1135–1141, doi:10.3762/bjoc.16.100

• the N-terminal domain (NTD). In vitro studies demonstrated that the progressive expansion of the length of the CAG repeat in NTD decreased its transactivation function. Exons 2 and 3 code the central DNA-binding domain and exons 4 to 8 code the C-terminal ligand-binding domain [14][15]. There are

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

• different substituents to control the electronic and steric requirements of the ligand. We focused on precursors that have functional groups of interest (F, Cl, CF3, NO2) as substituents in the 4-arylidene ring. In this way the final products will contain either a functional group that can be reacted

• -chelate bonding mode of the ortho-palladated oxazolone and the ability of the carboxylate group to act as a bridging ligand in related complexes, we propose for complexes 3a–f and 3h–j the ‘open-book’ structure shown in Scheme 1. The dimeric open-book structures of 3 can result in the formation of two

• isomers, the transoid (in which the two cyclopalladated oxazolones are in an anti arrangement) and the cisoid (syn arrangement). The presence of the two isomers in 3 is clear from the observation of two sets of signals due to the CF3CO2– ligand in the 19F NMR spectra. The major isomer shows one singlet

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

• presence of a catalytic amount of the ligand-free PdCl2 in environmentally friendly ethanol, achieve an efficient regio- and stereoselective synthesis of 4-methylene-3,4-dihydroisoquinolin-1(2H)-ones 4. It is worth noting that, during the preparation of this paper, a related article focused on the

Copper-based fluorinated reagents for the synthesis of CF₂R-containing molecules (R ≠ F)

• Louise Ruyet and
• Tatiana Besset

Beilstein J. Org. Chem. 2020, 16, 1051–1065, doi:10.3762/bjoc.16.92

• after reduction of the Ruppert–Prakash reagent with sodium borohydride [39]. The key of success was the use of bulky IPr and SIPr ligands to stabilize the organometallic species. Indeed, in the case of IPr as a ligand, the complex was stable in solution at room temperature for at least 24 hours. The

• ) and 1,10-phenanthroline as a ligand was crucial in their system. In 2012, Prakash also studied the in situ generation of CuCF2H from n-Bu3SnCF2H, the presence of DMF being the key to stabilize the CuCF2H intermediate [41] (Scheme 2). From these seminal works, a handful of reports was then published by

• -generated copper-based reagent (19 examples, up to 80% yield, Scheme 7e). With a similar method and in the presence of 1,10-phenanthroline as a ligand, the functionalization of alkenyl halides (8 examples, up to 82% yield), allyl halides (7 examples, up to 99% yield) and benzyl bromides (6 examples, up to

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

• protein–protein and protein–ligand interactions and consequently metabolic processes [20][21]. Fluorinated phenylalanines (FPhe) have been incorporated into various proteins and enzymes [22][23][24][25] with advantageous biophysical, chemical, and biological properties, and their effect on the stability

• 1b and 1c with iodoalanine 2 at room temperature using Pd2(dba)3 (2.5 mol %) and SPhos (5.0 mol %) provided excellent yields of (S)-phenylalanines 3a (70% yield) and 3b (80% yield), respectively. Such an efficiency improvement testifies to the suitability of SPhos as a ligand for these coupling

• -catalyzed asymmetric hydrogenation of the α-amidocinnamic acid 63 using the less frequently used ferrocene-based ligand Me-BoPhoz led to the N-acetyl-ʟ-phenylalanine derivative 64 with complete conversion and with 94% ee. The desired enantiomer (S)-65 was obtained as a single isomer (>99% ee) after

Copper-catalysed alkylation of heterocyclic acceptors with organometallic reagents

• Yafei Guo and
• Syuzanna R. Harutyunyan

Beilstein J. Org. Chem. 2020, 16, 1006–1021, doi:10.3762/bjoc.16.90

• -Bu2Zn, respectively). Later, T. Shibata and K. Endo prepared the same product (2c) with a higher enantioselectivity (97% ee) by using the multinuclear phosphorus ligand catalyst L2 [16]. Organoaluminium reagents are also commonly used organometallics in copper-catalysed ACA reactions. For example, in

• the total synthesis of the natural product (+)-myrtine with 14% overall yield (Scheme 1B) [17]. For this application, the highest yield (73%) and enantioselectivity (96% ee) were obtained using the chiral ligand L3 and a copper salt as the catalyst. Despite the fact that examples of high yield and

• enantioselectivity in addition reactions challenging. Nevertheless, Harutyunyan and co-workers introduced the first general catalytic methodology to access a wide variety of chiral piperidones in 2019, using Grignard reagents (Scheme 1C) [18]. Therein, a new catalytic system based on the ligand L4/Cu complex

Suzuki–Miyaura cross coupling is not an informative reaction to demonstrate the performance of new solvents

• James Sherwood

Beilstein J. Org. Chem. 2020, 16, 1001–1005, doi:10.3762/bjoc.16.89

• observed throughout unless noted subsequently. The first case study was adapted from that developed by Watson and co-workers [3][6]. The desired coupling is of 4-bromotoluene to produce 4-phenyltoluene, assisted by the inclusion of the bis(diphenylphosphino)ferrocene ligand and 3 equivalents of base

•  1b) [13]. Here, palladium acetate without an auxiliary ligand was used for a pre-catalyst and the base changed to potassium carbonate. Reaction conditions of 20 hours at 65 °C were decided after observing 11% conversion after 2 hours and 33% after 20 hours in NMP at room temperature. The majority of

• of Mizoroki–Heck reactions have a strong dependence on the dipolarity of the reaction medium, and the rate determining step can be controlled by the equivalents of ligand added, thereby eliminating one variable [8]. Reprotoxic solvents such as N,N-dimethylformamide (DMF) are routinely used in the

Pd-catalyzed asymmetric Suzuki–Miyaura coupling reactions for the synthesis of chiral biaryl compounds with a large steric substituent at the 2-position

• Yongsu Li,
• Bendu Pan,
• Xuefeng He,
• Wang Xia,
• Yaqi Zhang,
• Hao Liang,
• Chitreddy V. Subba Reddy,
• Rihui Cao and
• Liqin Qiu

Beilstein J. Org. Chem. 2020, 16, 966–973, doi:10.3762/bjoc.16.85

• bromobenzene substrates and the Pd···O interaction between carbonyl and palladium seem essential to achieve high enantioselectivity. Keywords: asymmetric catalysis; biaryls; monophosphine ligand; palladium catalyst; Suzuki–Miyaura couplings; Introduction Axially chiral molecules have received much attention

• (dba)3, 3.0 equivalents K3PO4 in THF at 50 °C for 72 h. The results show that the ligands have a large effect on the reaction. As listed in Table 1, the reaction was performed well and the product was obtained in 70% yield when using L1 (R)-MOP as the ligand, but the enantioselectivity was

• unsatisfactorily low (36% ee; Table 1, entry 1). After further examination of the ligands developed by our group (L2–L9), it was found that phosphine ligands with a large steric aryl group linked to a phosphorus atom are more effective than the ligand with a cyclohexyl group both in yield and enantioselectivity

Cation-induced ring-opening and oxidation reaction of photoreluctant spirooxazine–quinolizinium conjugates

• Phil M. Pithan,
• Sören Steup and
• Heiko Ihmels

Beilstein J. Org. Chem. 2020, 16, 904–916, doi:10.3762/bjoc.16.82

•  5B–F and Figure S6B–F, Supporting Information File 1). Notably, a third set of signals was detected when employing copper-to-ligand ratios of 0.25 and 0.50 (Figure 5B,C and Figure S6B,C, Supporting Information File 1, marked with green asterisks). While the signals in the aromatic region could not be

• reaction (Scheme 4, A). Moreover, this explanation is in agreement with the occurrence of the additional set of signals at small copper-to-ligand ratios (Figure 5B,C and Figure S6B,C, Supporting Information File 1, marked with green asterisks) and with the course of the spectrophotometric titration (Figure

Copper catalysis with redox-active ligands

• Agnideep Das,
• Yufeng Ren,
• Cheriehan Hessin and
• Marine Desage-El Murr

Beilstein J. Org. Chem. 2020, 16, 858–870, doi:10.3762/bjoc.16.77

• a neighboring tyrosine radical ligand for the shuttling of overall two protons and two electrons. This peculiar mechanism is enabled by transient storage of electronic density on the tyrosine ligands and perfectly illustrates the central role of ancillary pro-radical ligands in biological systems

• [2][3]. Inspired by the broad chemical repertoire of radical-ligand containing metalloenzymes, chemists have developed redox-active ligands as surrogates for the biologically occurring redox cofactors and this has translated into active developments in homogeneous catalysis [4]. The unique electronic

• interaction due to matching or inverted energy levels between metal and ligand leads to valence tautomerism [5][6][7][8], which paves the way for orchestrated electronic events occurring within the metal complex and influences the chemical reactivity of the complex. While the field of catalysis with redox