Suzuki Coupling Research Articles

M-Pyripentaphyrins(1.0.0.0.0): BIII Complexes and β-β Directly Linked Dimers.

m-Pyripentaphyrins(1.0.0.0.0) were synthesized by Suzuki-Miyaura coupling of 3,5-bis(5-borylpyrrol-2-yl)-BODIPY with 2,6-dibromopyridine. Upon treatment with PhBCl2, pyripentaphyrin 1 provided mono- and bis-BIII complexes sequentially. The Mono-BIII complex shows a distorted tetrahedral coordinated BIII with a σ-phenyl ligand on the BIII and the bis-BIII complex shows an additional distorted tetrahedral coordinated BIII with a B-H bond. Bromination of the pyripentaphyrins with N-bromosuccinimide (NBS) resulted in regioselective formation of 8-bromopyripentaphyrins, which were dimerized to 8,8'-linked dimers by reductive coupling with Ni(cod)2. While all these pyripentaphyrins are nonaromatic, they exhibit characteristic broad absorption bands at long wavelength near the NIR region, indicating the presence of effective macrocyclic conjugation.

Magnesium(II) porphyrazine with peripherally overloaded pyrrolyl substituents – Synthesis, optical and electrochemical characterization

Cross-coupling Suzuki-Miyaura reaction using Microwave Assisted Organic Synthesis (MAOS) approach of phenylboronic acid and magnesium(II) porphyrazines with peripheral dimethylamino and 3,4-dibromo-2,5-diphenylpyrrol-1-yl or 3-bromo-2,4,5-triphenylpyrrol-1-yl groups led to magnesium(II) porphyrazines with dimethylamino and 2,3,4,5-tetraphenylpyrrol-1-yl groups. MAOS approach was also used in the Paal-Knorr reaction to synthesise the modified diaminomaleonitrile intermediates. All intermediates and macrocycles were characterized using UV-Vis, 1H and 13C NMR spectroscopy, as well as ES or MALDI MS spectrometry. The optical and electrochemical properties of obtained porphyrazine macrocycles were assessed. It was found that the susceptibility of new macrocycles to oxidation/reduction processes analyzed by cyclic and differential pulse voltammetry depended on the presence of bromide and the number of phenyl substituents in the macrocyclic periphery.

Atroposelective Formal [2 + 5] Macrocyclization Synthesis for a Novel All-Hydrocarbon Cyclo[7] Meta-Benzene Macrocycle.

A novel axially chiral all-hydrocarbon cyclo[7] (1,3-(4,6-dimethyl)benzene (CDMB-7) was designed and synthesized using atroposelective[2 + 5] cyclization through Suzuki-Miyaura coupling. CDMB-7 adopts an irregular bowl-like shape with C2 symmetry and exhibits two diastereoisomers in its crystallographic structure. The conformational isomers of CDMB-7 racemates remain stable at high temperatures (393 K). High-performance liquid chromatography (HPLC) confirmed that a single chiral isomer will spontaneously undergo racemization within 30 min at room temperature. This finding opens up possibilities for achieving adaptive chirality in all-hydrocarbon cyclo[7] m-benzene macrocycles.

Buildup and Consumption of Species in Emulsion Droplets during Aqueous Suzuki Coupling Correlate with Yield.

Fluorescence lifetime imaging microscopy (FLIM) provides spatiotemporal resolution of the changing composition of emulsion droplets during aqueous-surfactant Suzuki coupling. In contrast to previous investigations, the present experiments characterize the full course of a catalytic chemical reaction, addressing key questions about reaction species buildup and correlating these microscale behaviors with bench-scale product yields. At low concentrations of (active) catalyst, droplet environments are stable; however, at higher concentrations, emulsion droplet environments change markedly. These changes are consistent with the buildup and consumption of reaction species inside the droplets. A combination of FLIM and bright-field imaging pinpoints limitations in catalyst solubility as controlling rate and degree of buildup of species in droplets. These solubility limitations are also identified as the cause of a reaction induction period and an origin of the rate-and-reproducibility advantage obtained by adding THF cosolvent. The subsequent mechanistic model from these data led to a bench-scale reaction optimization, wherein premixing the catalyst components bypasses the catalyst induction period, resulting in a faster reaction. The understanding generated by FLIM thus provides an early example of how visualizing changes in droplet compositions on the microscale during ongoing aqueous-organic reactions can be leveraged for enhancing efficiencies in bench-scale reactions.

Scalable Synthesis of ABBV-105 Enabled by Suzuki Coupling with Low Pd Loading, Ru-Catalyzed Asymmetric Hydrogenation, and Acylation Using Impinging Jet

Scalable Synthesis of ABBV-105 Enabled by Suzuki Coupling with Low Pd Loading, Ru-Catalyzed Asymmetric Hydrogenation, and Acylation Using Impinging Jet

Role of Ionic Liquids as Solvent & Catalyst for Heck and Suzuki Reactions: A Comprehensive Review

Role of Ionic Liquids as Solvent & Catalyst for Heck and Suzuki Reactions: A Comprehensive Review

An SN1-Approach to Cross-Coupling: Deoxygenative Arylation Facilitated by the β-Silicon Effect.

We report a dual metal-catalyzed method for the cross-coupling of unprotected alcohols by exploiting the β-Si effect. This deoxygenative Suzuki-Miyaura reaction tolerates a range of primary, secondary, and tertiary alcohol substrates along with diverse functional groups and heterocycles. Mechanistic experiments including KIE, VTNA, and Eyring analyses suggest the existence of a carbocation intermediate on the reaction pathway, consistent with a rare SN1 pathway for the activation of an electrophile in cross-coupling reactions. A novel bis-imidazolium N-heterocyclic carbene (NHC) ligand was found to be optimal for reactivity, and nickel(0)-, nickel(I)- and nickel(II)- complexes of this ligand were isolated and characterized. In contrast to more well-established shorter chain ligands, these long-chain NHCs are found to have characteristically large bite angles, which may be critical for enabling the deoxygenative arylation of aliphatic alcohols.

A synthesis of 1,3-dienes using a Ni(II) mediated Suzuki-Miyaura reaction

A synthesis of 1,3-dienes using a Ni(II) mediated Suzuki-Miyaura reaction

The first total syntheses of lorneic acids C and D and improved synthetic routes to lorneic acids A and J

We report the first total syntheses of lorneic acids C and D, each in 4 steps, from commercially-available 2-bromo-5-methyl benzaldehyde in 61 % and 36 % overall yields, respectively. A key feature of the syntheses includes a Suzuki cross-coupling to introduce the carboxylic sidearms in the natural products. Additionally, our group previously reported the construction of lorneic acids A and J, in 7 steps, with 23 % overall yields that included a lengthy 3-step sequence of reactions for the 1-carbon homologation of the allylic alcohols. Herein, we report second-generation synthetic routes towards lorneic acids A and J, each in 5 steps with 50 % and 46 % overall yields. In this case, a palladium-catalyzed carboxylation of allylic alcohol intermediates with formic acid secured the carboxylic acid sidearms. The new and improved routes shorten the total syntheses by 2 steps and double the yields of both natural products.

Synthesis of polysubstituted pyrazoles and their biological applications

Novel library of pyrazole derivatives (6a–k) from substituted 4-dioxaborolanyl-1H-pyrazole and halo benzaldehyde through simultaneous Suzuki reaction, nucleophilic addition, and hydrolysis under moderate reaction conditions. The desired compounds 6a–k have been formed in good to high yield. All the compound structures were characterized by analytical and spectral (1H NMR,13C NMR and MS) studies. Furthermore, the evaluation of biological activity of synthesized molecules.

Synthesis of spiroindoline derivatives and biphenyl compounds in green solvent via a “capture–release” mechanism using modified polyacrylonitrile fiber as a catalyst

Green synthesis of critical bioactive molecules and fine chemicals is attracting increasing interest. This study investigates the use of two distinct functionalized polyacrylonitrile (PAN) fibers (PANEDBPF and PANEDBP-Pd0F) as effective catalysts in a green solvent comprising ethanol and water. Firstly, a PAN fiber was modified using 2-(diphenylphosphino) ethylamine, a strongly nucleophilic phosphine compound, to obtain PANEDBPF. Spiroindoline derivatives were obtained in 98 % yields when the reaction was conducted using 5 mol% of PANEDBPF as the catalyst at 70 °C for 30 min. Next, we loaded PdNPs onto PANEDBPF to obtain PANEDBP-Pd0F. When the Suzuki coupling reaction was conducted at room temperature (25 °C) using 0.5 mol% of PANEDBP-Pd0F, the products were obtained in an extremely high yield of 99 %. Additionally, the unique enrichment of the substrate by the functionalized fibers during the reaction and the subsequent release of the product from the microenvironment conform to the “capture–release” reaction mode of catalysis. Both PANEDBPF and PANEDBP-Pd0F demonstrated good gram-scale amplification, repeatability, catalytic activity, and stability. Hence, they are highly promising candidates for green chemistry applications.

A highly selective and sensitive oligomers-based fluorescent sensor for Cu2+ detection in aqueous solution incorporating pillar[5]arene and imidazo[4,5-f][1,10]phenanthroline moieties

A conjugated oligomers (Co-P[5]ImPhen) containing pillar[5]arene (P[5]) unit as fluorophore and 1H imidazo[4,5-f][1,10]phenanthroline (ImPhen) unit as recognition group was designed and synthesized by Suzuki coupling. The Co-P[5]ImPhen has good fluorescent performance in DMSO aqueous solutions. The Co-P[5]ImPhen has an excellent selectivity and sensitivity for Cu2+ detection in DMSO/H2O (1:3, v:v) solution while showing fluorescence quenching response to Cu2+ (1 − I/I0= 94.2%) and excellent anti-interference ability against paraquat analogs and metal ions. Additionally, the Stern-Volmer quenching constant (Ksv) was calculated to be 2.544 × 106 M-1 by fluorescence titration, indicating that the oligomer has strong binding capacity to Cu2+. The detection limit for Cu2+ was remarkably low (1.17 × 10-10 M). The binding mechanism of Co-P[5]ImPhen with Cu2+ was verified utilizing 1H NMR spectra and quantum chemical calculations. The study indicated that the Co-P[5]ImPhen interacts with Cu2+ primarily through two nitrogen atoms on phenanthroline. Furthermore, the oligomers Co-P[5]ImPhen showed potential application in the detection of Cu2+ in practical samples.

Magnetic PdNi@CN as a versatile catalyst for Suzuki reaction and 4-nitrophenol reduction

Palladium-based non-homogeneous catalysts have attracted considerable attention due to their high catalytic efficiency and adaptability. However, they still face the challenges of long reaction routes and poor cycling stability. An economical, efficient, stable and environmentally friendly catalyst PdNi@CN was prepared by loading nickel-palladium nanoparticles onto nitrogen-doped carbon functionalized carrier material. The catalyst was thoroughly characterized using XRD, XPS, SEM, TEM, VSM, and ICP. PdNi@CN could efficiently catalyze the Suzuki coupling reaction (Iodobenzene and phenylboronic acid, 97 % yield, TON (Turnover Number)=1.62 × 102, TOF (Turnover Frequency)=2.43 × 102 h-1). Furthermore, PdNi@CN exhibited high activity in the reduction of 4-nitrophenol (4-NP, Kapp=8.01 × 10–2 s-1). After five cycles of catalysis, the conversion of 4-NP still reached 95 %, demonstrating the excellent structural stability and high catalytic performance of PdNi@CN.

Helicene Appended Benzothiadiazoles as Chiral Emitters.

A homologous series of 4,7-bis(aryl) substituted benzothiadiazole (BTD) compounds, containing the helicenic derivatives bis([4]helicene), bis([5]helicene) and bis([6]helicene), have been prepared upon a double Suzuki coupling between 3,6-bis(pinacolyl-borane)-BTD and the corresponding bromo-aryl precursors. The single crystal X-ray structure of the bis([4]helicene) compound shows the existence of both helicities (M) and (P) on the same molecule. All the compounds of the series are highly emissive in solution, with quantum yields of the emission ranging from 50 to 91 %. The enantiopure compounds (M,M) and (P,P) for the BTD-bis([6]helicene) have been prepared from the corresponding enantiopure 2-bromo-[6]helicene precursors. Their chiroptical properties have been investigated in correlation with density functional theory (DFT) calculations, which allowed to confidently assign the absolute configuration of the helicene arms and to characterize the different electronic transitions, including the low energy charge transfer excitation from helicenes to BTD. The enantiomerically pure fluorophores (M,M)- and (P,P)-BTD-bis([6]helicene), which exist in solution as two main conformers, according to the DFT calculations, show CPL activity in solution, with glum factors of ≈1.7×10-3 at λem=525 nm, and also in the solid state, with glum factors of ≈1.2×10-3 in spite of the strong decrease of the quantum efficiency.

Double-bridged N–B←N bipyridyl-based airfoil-shaped small molecule dyes: π-bridge regulation on photovoltaic performance

The double-bridged N–B←N bipyridine unit (BNBP) with boron-nitrogen covalent bond and coordination bond can reduce the electronic energy level of the π-conjugated system, resulting in a reduction of band gap and a red shift in the absorption spectrum. Embedding the BNBP building block into organic optoelectronic materials provides a novel possibility in molecule design. In this paper, under the guidance of density functional theory (DFT) calculations, a series of 3D “airfoil-shaped” small molecule donors (SMDs) have been designed and successfully synthesized through Sonogashira, Suzuki and Stille coupling reactions. BNBP is adopted as the central electron-withdrawing unit and strong electron-rich triphenylamine (TPA) as the terminal group. The novel “airfoil-shaped” structure plays a supporting role in reducing the carrier recombination in the active layer. It reveals that molecular design engineering can achieve the expected results by the following steps: Firstly, the introduction of electron-rich alkoxy groups into the end of TPA through side chain engineering helps to improve the solubility and film-forming properties of the materials. Then, the π-bridge regulation not only extends the conjugate structure, but also plays a crucial role in the regulation of photovoltaic properties. It is worth noting that the compound BNBP(3TTPA)2 was synthesized by introducing thiophene oligomer into BNBP-based SMDs for the first time. Finally, the compound BNBP(EDPPTPA)2 was constructed by combining BNBP with DPP dye unit. Its narrow band gap is only 1.36 eV, which is one of the narrowest band gaps in small molecular organic-boron materials. In particular, compared with the starting compound BNBP(ETPA)2, the synergistic effects of DPP and BNBP broaden the edge absorption wavelength to 814 nm, resulting in a red shift of 170 nm. The power conversion efficiency (PCE) of 4.48 % is obtained in BNBP(EDPPTPA)2-based bulk heterojunction (BHJ) organic solar cells (OSCs), which is more than twice that of reference compound BNBP(ETPA)2. This work provides important references for the future development of 3D BNBP-based organic-boron SMDs and the structural regulation of materials through molecular engineering.

Design and synthesis of new nicotinamide derivatives generated via Suzuki Miyaura coupling as potential anticancer hits targeting pancreatic cancer cell line MIA PaCa-2

Pancreatic cancer is one of the most fatal malignancies with low survival rate and spreads asymptomatically due to the intensive involvement and expression of PARP1 protein. Nicotinamide is recognised as an efficient ring system in the treatment of pancreatic cancer because of its uses in both cellular and biological processes. In this investigation, 3-methoxyphenyl nicotinamide derivatives were synthesised utilizing a palladium-catalysed Suzuki-Miyaura coupling, and their confirmation has been identified by spectroscopic techniques (HRMS, 1H NMR & 13C NMR). The confirmed compounds (5a-f) were introduced to in-vitro cytotoxic studies using the MTT assay, which demonstrated that 5d and 5f were potent against MIA PaCa-2 cell line with IC50 values of 26±1.21µM and 18.61±0.20µM. The compounds 5d and 5f were also examined against HEK 293 cells, which exhibited a diminished antiproliferative effect with an IC50 values of 82.6µM and 138.07µM, respectively. Consequently, 5d and 5f were found to be safer with reduced antiproliferative effect. The MTT assay results were validated by the molecular docking and ADMET studies, which revealed the binding affinities of compounds 5d and 5f are -9.1 and -9.4 Kcal/mol. Overall, the designed and synthesised conjugates 5d and 5f demonstrated a viable lead for the investigation of new chemotherapeutic drugs against pancreatic cancer in this study.

Design and synthesis of novel Thiazolo[5,4-b]pyridine derivatives as potent and selective EGFR-TK inhibitors targeting resistance Mutations in non-small cell lung cancer

A novel series of substituted thiazolo[5,4-b]pyridine analogues were rationally designed and synthesized via a multi-step synthetic pathway, including Suzuki cross-coupling reaction. The anticancer activity of all forty-five synthesized derivatives was evaluated against HCC827, H1975, and A549 cancer cell lines utilizing the standard MTT assay. A significant number of the thiazolo[5,4-b]pyridine derivatives exhibited potent anticancer activity. Notably, compounds 10b, 10c, 10h, 10i, and 10k emerged as the most promising anticancer agents. The lead compound, N-(3-(6-(2-aminopyrimidin-5-yl)thiazolo[5,4-b]pyridin-2-yl)-2-methylphenyl)-2,5-difluorobenzenesulfonamide (10k), displayed remarkable potency with IC50 values of 0.010 μM, 0.08 μM, and 0.82 μM against the HCC827, NCI–H1975 and A-549 cancer cell lines, respectively, which were comparable to the clinically approved drug Osimertinib. Importantly, the potent derivatives 10b, 10c, 10h, 10i, and 10k exhibited selective cytotoxicity towards cancer cells and showing no toxicity against the normal BEAS-2B cell line at concentrations exceeding 35 μM. Mechanistic studies revealed that the active compound 10k acts as an EGFR-TK autophosphorylation inhibitor in HCC827 cells. Furthermore, apoptosis assays demonstrated that compound 10k induced substantial early apoptosis (31.9 %) and late apoptosis (8.8 %) in cancer cells, in contrast to the control condition exhibiting only 2.0 % early and 1.6 % late apoptosis. Molecular docking simulations of the synthesized compounds revealed that they formed essential hinge interactions and established hydrogen bonding with Cys797, indicating potential target engagement. These findings highlight the potential of the synthesized thiazolo [(Woodburn, 1999; Zigrossi et al., 2022) 5,45,4-b]pyridine derivatives as promising anticancer agents, warranting further investigation for the development of novel targeted therapies against non-small cell lung cancer.

A Rationally Designed Iron(II) Catalyst for C(sp3)−C(sp2) and C(sp3)−C(sp3) Suzuki–Miyaura Cross‐Coupling

AbstractDespite the paramount importance of the Suzuki–Miyaura coupling (SMC) in academia and industry, and the great promise of iron to offer sustainable catalysis, iron‐catalyzed SMC involving sp3‐hybridized partners is still in its infancy. We herein report the development of a versatile, well‐defined electron‐deficient anilido‐aldimine iron(II) catalyst. This catalyst effectively performed C(sp3)−C(sp2) and C(sp3)−C(sp3) SMC of alkyl halide electrophiles and (hetero)aryl boronic ester and alkyl borane nucleophiles respectively, in the presence of a lithium amide base. These couplings operated under mild reaction conditions and displayed wide functional group compatibility including various medicinally relevant N‐, O‐ and S‐based heterocycles. They also tolerated primary, secondary and tertiary alkyl halides (Br, Cl, I), electron‐neutral, ‐rich and ‐poor boronic esters and primary and secondary alkyl boranes. Our methodology could be directly and efficiently applied to synthesize key intermediates relevant to pharmaceuticals and a potential drug candidate. For C(sp3)−C(sp2) couplings, radical probe experiments militated in favor of a carbon‐centered radical derived from the electrophile. At the same time, reactions run with a pre‐formed activated boron nucleophile coupled to competition experiments supported the involvement of neutral, rather than an anionic, (hetero)aryl boronic ester in the key transmetalation step.

A Rationally Designed Iron(II) Catalyst for C(sp3)-C(sp2) and C(sp3)-C(sp3) Suzuki-Miyaura Cross-Coupling.

Despite the paramount importance of the Suzuki-Miyaura coupling (SMC) in academia and industry, and the great promise of iron to offer sustainable catalysis, iron-catalyzed SMC involving sp3-hybridized partners is still in its infancy. We herein report the development of a versatile, well-defined electron-deficient anilido-aldimine iron(II) catalyst. This catalyst effectively performed C(sp3)-C(sp2) and C(sp3)-C(sp3) SMC of alkyl halide electrophiles and (hetero)aryl boronic ester and alkyl borane nucleophiles respectively, in the presence of a lithium amide base. These couplings operated under mild reaction conditions and displayed wide functional group compatibility including various medicinally relevant N-, O- and S-based heterocycles. They also tolerated primary, secondary and tertiary alkyl halides (Br, Cl, I), electron-neutral, -rich and -poor boronic esters and primary and secondary alkyl boranes. Our methodology could be directly and efficiently applied to synthesize key intermediates relevant to pharmaceuticals and a potential drug candidate. For C(sp3)-C(sp2) couplings, radical probe experiments militated in favor of a carbon-centered radical derived from the electrophile. At the same time, reactions run with a pre-formed activated boron nucleophile coupled to competition experiments supported the involvement of neutral, rather than an anionic, (hetero)aryl boronic ester in the key transmetalation step.

Phase transfer catalysts shift the pathway to transmetalation in biphasic Suzuki-Miyaura cross-couplings

The Suzuki-Miyaura coupling is a widely used C-C bond forming reaction. Numerous mechanistic studies have enabled the use of low catalyst loadings and broad functional group tolerance. However, the dominant mode of transmetalation remains controversial and likely depends on the conditions employed. Herein we detail a mechanistic study of the palladium-catalyzed Suzuki-Miyaura coupling under biphasic conditions. The use of phase transfer catalysts results in a remarkable 12-fold rate enhancement in the targeted system. A shift from an oxo-palladium based transmetalation to a boronate-based pathway lies at the root of this activity. Furthermore, a study of the impact of different water loadings reveals reducing the proportion of the aqueous phase increases the reaction rate, contrary to reaction conditions typically employed in the literature. The importance of these findings is highlighted by achieving an exceptionally broad substrate scope with benzylic electrophiles using a 10-fold reduction in catalyst loading relative to literature precedent.