Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

• solution and in the solid state [127]. Furthermore, even sugar-functionalized pyrazoles have been accessed by this approach [128], and it was readily implemented in a continuous flow reactor [129]. Besides traditional Sonogashira catalyst systems, highly reactive and reusable immobilized Pd-complexes, such

Synthesis of 7-azabicyclo[4.3.1]decane ring systems from tricarbonyl(tropone)iron via intramolecular Heck reactions

• Aaron H. Shoemaker,
• Elizabeth A. Foker,
• Elena P. Uttaro,
• Sarah K. Beitel and
• Daniel R. Griffith

Beilstein J. Org. Chem. 2023, 19, 1615–1619, doi:10.3762/bjoc.19.118

• by Bennasar, which elevated the yield to 76% (Table 1, entry 7) [10]. It has been postulated [21] that phenoxide is capable of stabilizing one or more of the intermediate Pd complexes, which may account for the higher yield. Interestingly, applying these conditions to the vinyl bromide 7 resulted in

Sequential hydrozirconation/Pd-catalyzed cross coupling of acyl chlorides towards conjugated (2E,4E)-dienones

• Benedikt Kolb,
• Daniela Silva dos Santos,
• Sanja Krause,
• Anna Zens and
• Sabine Laschat

Beilstein J. Org. Chem. 2023, 19, 176–185, doi:10.3762/bjoc.19.17

• optimize the second step of the reaction sequence, several Pd complexes were tested in the reaction of 25a with 26a. However, the yields of the dienone 27a decreased considerably, when (Ph3P)2PdCl2 was replaced by other Pd complexes (Table 3, entries 2–5). In particular, (AntPhos)2Pd(dba) and (XPhos)2Pd

Biological properties and conformational studies of amphiphilic Pd(II) and Ni(II) complexes bearing functionalized aroylaminocarbo-N-thioylpyrrolinate units

• Samet Poyraz,
• Samet Belveren,
• Sabriye Aydınoğlu,
• Mahmut Ulger,
• Abel de Cózar,
• Maria de Gracia Retamosa,
• Jose M. Sansano and
• H. Ali Döndaş

Beilstein J. Org. Chem. 2021, 17, 2812–2821, doi:10.3762/bjoc.17.192

• signals in NMR spectra (corresponding to conformer A) would be observed. For L1-Pd complexes, the aggregate included two energetically accessible rotamers at room temperature (energetic difference of +2.2 kcal·mol−1, Figure 1). Therefore, the duplicated set of signals in the 1H NMR was justified. We

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• given combination of enone and arylboronic acid. Keywords: asymmetric reaction; boronic acid; conjugated enones; chromones; enantioselective catalysis; Michael addition; Pd complexes; Introduction The asymmetric 1,4-addition of arylboronic acids to conjugated cyclic enones and chromones is a very

• %; 85% ee), but the reaction times were very short (Scheme 7) [41]. In 2011, the groups of Hayashi and Chujo studied Pd complexes of diphosphacrown ethers [42]. The macrocyclic Pd complex PdL5 in combination with AgSbF6 or AgOTf was tested for the addition reaction of various arylboronic acids to 2

• systematic study of phosphine-based Pd complexes was done by Wong et al. in 2014. The palladacycle PdL6 was used in combination with triphenylphosphine and K3PO4 acting as a base. The highest enantioselectivity of 99% ee of a model addition of phenylboronic acid to 2-cyclohexenone was achieved in dioxane as

Silver-catalyzed synthesis of β-fluorovinylphosphonates by phosphonofluorination of aromatic alkynes

• Yajing Zhang,
• Qingshan Tian,
• Guozhu Zhang and
• Dayong Zhang

Beilstein J. Org. Chem. 2020, 16, 3086–3092, doi:10.3762/bjoc.16.258

• -fluorovinylphosphonates under mild conditions. First, we examined the catalytic activity of various transition metal catalysts, including Au, Ag, Cu, Rh, and Pd complexes (Supporting Information File 1). Among these metal salts, silver salts, especially AgOAc, were the most effective catalysts for generating the desired

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

• released active species at the end of the reaction, in what has been called a “boomerang” mechanism [16][17]. Here, we report our efforts aiming a rational development for Negishi catalysts based on NHC–Pd complexes in conjunction with supported ionic liquid-like phases to enhance their catalytic stability

• Table 1). The slightly lower value of the Pd loading is likely to be related to the partial formation of 2:1 NHC/Pd complexes. The experimental details for the synthesis of 2a,b, 3a,b and 4a,b are given in Supporting Information File 1. The Negishi reaction of benzylzinc bromide (5) and methyl 4

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

• of the free species [27] and on using Pd complexes as templates [28][29][30]. The latter approach has shown good potential as a synthetic tool because it allows 1,3-diaminotruxillic derivatives to be obtained in a fully regio- and stereoselective way (only the ε-isomer is obtained). The process

• ], did not produce the expected cyclobutanes or gave only very low conversions (<5%) after long reaction times (96 h). As this reactivity was poor, it was decided to attempt the reaction using Pd complexes as templates [28][29][30]. The first step in this process was to study the C–H bond activation in

Synthesis and characterization of π–extended “earring” subporphyrins

• Haiyan Guan,
• Mingbo Zhou,
• Bangshao Yin,
• Ling Xu and
• Jianxin Song

Beilstein J. Org. Chem. 2018, 14, 1956–1960, doi:10.3762/bjoc.14.170

• corresponding Pd complexes exhibited remarkably near-infrared absorptions. Based on our previous work, we herein designed a subporphyrin with one “earring”. The different geometry and properties could be envisioned due to the bowl-shaped structure and 14π-electron configuration of subporphyrin. To construct the

Heterogeneous Pd catalysts as emulsifiers in Pickering emulsions for integrated multistep synthesis in flow chemistry

• Katharina Hiebler,
• Georg J. Lichtenegger,
• Manuel C. Maier,
• Eun Sung Park,
• Renie Gonzales-Groom,
• Bernard P. Binks and
• Heidrun Gruber-Woelfler

Beilstein J. Org. Chem. 2018, 14, 648–658, doi:10.3762/bjoc.14.52

• palladium by ligands which are covalently bound to the support material [12]. One example of such a catalyst was reported by our group using a bis(oxazoline) ligand bonded to 3-mercaptopropyl-functionalised silica [20]. Alternatively, the use of unsupported Pd nanoparticles or encapsulated Pd complexes are

An efficient Pd–NHC catalyst system in situ generated from Na₂PdCl₄ and PEG-functionalized imidazolium salts for Mizoroki–Heck reactions in water

• Nan Sun,
• Meng Chen,
• Liqun Jin,
• Wei Zhao,
• Baoxiang Hu,
• Zhenlu Shen and
• Xinquan Hu

Beilstein J. Org. Chem. 2017, 13, 1735–1744, doi:10.3762/bjoc.13.168

• conditions in hand, we then further compared the catalytic performance of those Pd-complexes derived from phenyl and naphthyl analogues L2 and L3 with that of pyridine functionalized NHC precursor L1. A kinetic study of the coupling between 4-bromoacetophenone (1a) and styrene (2a) was performed in the

Methylpalladium complexes with pyrimidine-functionalized N-heterocyclic carbene ligands

• Dirk Meyer and
• Thomas Strassner

Beilstein J. Org. Chem. 2016, 12, 1557–1565, doi:10.3762/bjoc.12.150

• ), [(tmeda)Pd(CH3)2], an approach which is frequently used to synthesize dimethyl Pd complexes [50][51][52][53]. Deprotonation of the imidazolium salt 3 and subsequent conversion of the free carbene with [(tmeda)Pd(CH3)2] gave the desired dimethylpalladium(II) complex 15 (Scheme 5) in 47% yield. Conclusion

Ring-whizzing in polyene-PtL₂ complexes revisited

• Oluwakemi A. Oloba-Whenu,
• Thomas A. Albright and
• Chirine Soubra-Ghaoui

Beilstein J. Org. Chem. 2016, 12, 1410–1420, doi:10.3762/bjoc.12.135

• transition state for ring whizzing. The activation barrier was computed to be 3.2 kcal/mol. Barriers from 10.5 to 7.6 kcal/mol were found for the Pd complexes [49]. Interestingly an η1 transition structure with one imaginary frequency was also discovered. It was found to be 7.2 kcal/mol above the ground

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• organic synthesis and has showed its usefulness in the allylation of isatins. In 2014, Song and co-workers designed the chiral CNN (three atoms attched to the palladium) pincer Pd complexes, which were proved to be efficient in catalyzing the enantioselective allylation of isatins with allyltributytin

Spiro-fused carbohydrate oxazoline ligands: Synthesis and application as enantio-discrimination agents in asymmetric allylic alkylation

• Jochen Kraft,
• Martin Golkowski and
• Thomas Ziegler

Beilstein J. Org. Chem. 2016, 12, 166–171, doi:10.3762/bjoc.12.18

• with Pd(cod)Cl2 (Figure 1). Single crystal X-ray diffraction of these Pd complexes revealed some interesting structural features in terms of ligand–metal bite angles and shielding of the palladium center by the carbohydrate scaffold from one specific side [17]. For example, we concluded from the

New palladium–oxazoline complexes: Synthesis and evaluation of the optical properties and the catalytic power during the oxidation of textile dyes

• Rym Hassani,
• Mahjoub Jabli,
• Yakdhane Kacem,
• Jérôme Marrot,
• Damien Prim and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2015, 11, 1175–1186, doi:10.3762/bjoc.11.132

• PdII ions, leading to the adsorption of dyes. Moreover, the decolorization of the solution by Pd and Pd complexes has also been applied [23]. In this paper, we report the synthesis and characterization of some new palladacycles. Optical properties were determined and the catalytic activity of these

Highly selective palladium–benzothiazole carbene-catalyzed allylation of active methylene compounds under neutral conditions

• Antonio Monopoli,
• Pietro Cotugno,
• Carlo G. Zambonin,
• Francesco Ciminale and
• Angelo Nacci

Beilstein J. Org. Chem. 2015, 11, 994–999, doi:10.3762/bjoc.11.111

• heterocyclic ring enables the tuning of their steric and electronic properties affecting the catalytic activity of the resulting metal complex [26][27][28][29]. Although NHC–Pd complexes have been employed in many C–C bond-forming reactions, to the best of our knowledge they have been scarcely applied to the

Palladium(II)-catalyzed Heck reaction of aryl halides and arylboronic acids with olefins under mild conditions

• Tanveer Mahamadali Shaikh and
• Fung-E Hong

Beilstein J. Org. Chem. 2013, 9, 1578–1588, doi:10.3762/bjoc.9.180

• -rich and electron-poor olefins, were converted smoothly to the targeted products in high yields. Compared with the existing approaches employing SPO–Pd complexes in a Heck reaction, the current strategy features mild reaction conditions and broad substrate scope. Furthermore, we described the coupling

Synthesis and structure of trans-bis(1,4-dimesityl-3-methyl-1,2,3-triazol-5-ylidene)palladium(II) dichloride and diacetate. Suzuki–Miyaura coupling of polybromoarenes with high catalytic turnover efficiencies

• Jeelani Basha Shaik,
• Venkatachalam Ramkumar,
• Babu Varghese and
• Sethuraman Sankararaman

Beilstein J. Org. Chem. 2013, 9, 698–704, doi:10.3762/bjoc.9.79

• coupling of polybromoarenes using complex 1 Complexes of palladium-mesoionic NHCs have been shown to be catalytically much more active than the corresponding complexes with normal NHCs (i.e., Pd complexes of 1,2,3-triazolylidene versus imidazolylidene ligands) in C–C bond-forming coupling reactions [28

• ), 6.86 (s, 4H); 3.52 and 2.83 (AA’BB’ pattern, 8H); 13C NMR (125 MHz, CDCl3) δ 143.7, 139.5, 137.5, 132.6, 129.4 (q, J = 32.6 Hz), 129.2, 124.3 (q, J = 270 Hz), 33.4; HRMS (ESI–QTOF): m/z calcd for C44H29F12 785.2078, found 785.2077. Structure of Pd complexes 1–4. ORTEP representation of the structure of

• complex 1 in the crystal (35% probability ellipsoids). Hydrogens are omitted for clarity. ORTEP representation of the structure of complex 2 in the crystal (35% probability ellipsoids). Hydrogens are omitted for clarity. Synthesis of Pd complexes 1 and 2. Multiple Suzuki–Miyaura coupling of

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

N-Heterocyclic carbene–palladium(II)-1-methylimidazole complex catalyzed Mizoroki–Heck reaction of aryl chlorides with styrenes

• Ting-Ting Gao,
• Ai-Ping Jin and
• Li-Xiong Shao

Beilstein J. Org. Chem. 2012, 8, 1916–1919, doi:10.3762/bjoc.8.222

• ]. Consequently, since the seminal papers reported by Herrmann and co-workers [16][17], the NHC–Pd complexes have become a strong challenge to the phosphine–metal complexes in the Mizoroki–Heck reaction. Among the electrophiles participating in the NHC–Pd-complex-catalyzed Mizoroki–Heck reaction, organic iodides

• applications due to their lower cost and the widest availability [26][27][28]. However, organic chlorides, especially the deactivated ones, are generally unreactive in the NHC–Pd-complex-catalyzed Mizoroki-Heck reaction [29][30][31]. Furthermore, synthetic routes for the above mentioned NHC–Pd complexes that

Synthesis of conformationally restricted glutamate and glutamine derivatives from carbonylation of orthopalladated phenylglycine derivatives

• Esteban P. Urriolabeitia,
• Eduardo Laga and
• Carlos Cativiela

Beilstein J. Org. Chem. 2012, 8, 1569–1575, doi:10.3762/bjoc.8.179

• reactivity found for 1, and shown in Scheme 3, when compared to related Pd complexes previously reported by us [12], resumed in Scheme 1. Therefore, the synthesis of the methyl (1H)-isoindolin-1-one-3-carboxylates by carbonylation of [Pd(μ-Cl)(C6H4CH(CO2Me)NH2-2)]2 occurs by C–N coupling, irrespective of the