Palladium-catalyzed Cross-coupling Reactions Research Articles

Palladium-Catalyzed Cross-Coupling Reactions: A Powerful Tool for the Synthesis of Agrochemicals.

Pd-catalyzed cross-coupling reactions have become essential tools for the construction of carbon-carbon and carbon-heteroatom bonds. Over the last three decades, great efforts have been made with cross-coupling chemistry in the discovery, development, and commercialization of innovative new pharmaceuticals and agrochemicals (mainly herbicides, fungicides, and insecticides). In view of the growing interest in both modern crop protection and cross-coupling chemistry, this review gives a comprehensive overview of the successful applications of various Pd-catalyzed cross-coupling methodologies, which have been implemented as key steps in the synthesis of agrochemicals (on R&D and pilot-plant scales) such as the Heck, Suzuki, Sonogashira, Stille, and Negishi reactions, as well as decarboxylative, carbonylative, α-arylative, and carbon-nitrogen bond bond-forming cross-coupling reactions. Some perspectives and challenges for these catalytic coupling processes in the discovery of agrochemicals are briefly discussed in the final section. The examples chosen demonstrate that cross-coupling chemistry approaches open-up new, low-cost, and more efficient industrial routes to existing agrochemicals, and such methods also have the capability to lead the new generation of pesticides with novel modes of action for sustainable crop protection.

One-Pot Conversion of Aldehydes and Ketones into 1-Substituted and 1,4-Disubstituted 1,3-Enynes

Sequential treatment of 2,3-dichloropropene with magnesium and n-BuLi generates the operational equivalent of 1,3-dilithiopropyne, which upon treatment with aldehydes or ketones, produces the corresponding alkoxy lithium acetylide intermediates. Reaction of this alkoxide with tosyl chloride, and t-BuLi produces 1-substituted, or 1,1-disubstituted 1,3-enynes in a one-pot reaction. When this lithium acetylide intermediates, obtained by this procedure, were used to perform palladium-catalyzed cross-coupling reactions, followed by addition of thionyl chloride and pyridine, 1,4-disubstituted or 1,1,4-trisubstituted 1,3-enynes were obtained in a one-pot protocol.

A heterogeneous single-atom palladium catalyst surpassing homogeneous systems for Suzuki coupling.

Palladium-catalysed cross-coupling reactions, central tools in fine-chemical synthesis, predominantly employ soluble metal complexes despite recognized challenges with product purification and catalyst reusability1-3. Attempts to tether these homogeneous catalysts on insoluble carriers have been thwarted by suboptimal stability, which leads to a progressively worsening performance due to metal leaching or clustering4. The alternative application of supported Pd nanoparticles has faced limitations because of insufficient activity under the mild conditions required to avoid thermal degradation of the substrates or products. Single-atom heterogeneous catalysts lie at the frontier5-18. Here, we show that the Pd atoms anchored on exfoliated graphitic carbon nitride (Pd-ECN) capture the advantages of both worlds, as they comprise a solid catalyst that matches the high chemoselectivity and broad functional group tolerance of state-of-the-art homogeneous catalysts for Suzuki couplings, and also demonstrate a robust stability in flow. The adaptive coordination environment within the macroheterocycles of ECN facilitates each catalytic step. The findings illustrate the exciting opportunities presented by nanostructuring single atoms in solid hosts for catalytic processes that remain difficult to heterogenize.

Divergent Synthesis of Marine Natural Products Siphonodictyal B, Corallidictyals C/D, and Liphagal Based on the Early Presence of an Aldehyde Group Instead of a Late-Stage Introduction.

An iodine-promoted sunlight-induced olefin Z/ E isomerization reaction together with a palladium-catalyzed direct cross-coupling reaction of a drimanal hydrazone and an iodobenzaldehyde, without touching the aromatic aldehyde group, facilitated a divergent and expeditious access to bioactive marine natural products siphonodictyal B, corallidictyals C/D, and liphagal based on the early presence of an aldehyde group instead of a late-stage introduction.

Synthesis of anti-tubercular marine alkaloids denigrins A and B

The first synthesis of anti-tubercular marine alkaloids denigrins A and B were accomplished in three and five steps and 62% and 31% overall yields respectively, from maleic anhydride. The key features of the synthesis include efficient Mizoroki-Heck reaction, geometry-controlled vinylogous aldol condensation, and one-pot lactamization. The synthesis first demonstrates the serviceability of maleic anhydride in palladium-catalyzed cross-coupling reactions with diaryliodonium salt.

A novel D-π-A BODIPY-stilbene with aggregation-induced red emission and Its interaction with bovine serum albumin

Novel D-π-A conjugated dyes of BODIPY-stilbenes constructed through palladium catalyzed cross coupling reaction, are found to be promising red AIE-active building blocks. Three new aggregation-induced emission enhancement (AIEE) chromophores BODIPY-stilbene 1, 2, 3 with stilbene-based donor-π bridge-acceptor BODIPY (D-π-A) structure have been built, which emit red fluorescence in the solid state with a maximum emission wavelength at 657, 626 and 656 nm, respectively. BODIPY-stilbene 1 show weak fluorescence in pure THF (ΦF=0.05). However, the fluorescence intensities in 90% water fraction THF/H2O mixtures (λem = 636 nm) increased obviously, with the quantum yields of up to 0.10. Meanwhile, BODIPY stilbene 1 with terminal carboxylic acid can achieve fast detection for bovine serum albumin (BSA) based on the AIEE. The red fluorescence intensity of BODIPY-stilbene 1 in the test system at 636 nm is increased by 5.7-fold when the concentration of BSA increased from 0 to50 μM.

Pyrene-Based Conjugated Polymer/Bi2MoO6 Z-Scheme Hybrids: Facile Construction and Sustainable Enhanced Photocatalytic Performance in Ciprofloxacin and Cr(VI) Removal under Visible Light Irradiation

The search for appropriate materials with favorable staggered energy band arrangements is important and is a great challenge in order to fabricate Z-scheme photocatalysts with high activity in visible light. In this study, we demonstrated a facile and feasible strategy to construct highly active organic–inorganic Z-scheme hybrids (P-BMO) with linear pyrene-based conjugated polymer (P17-E) and Bi2MoO6, via an in-situ palladium-catalyzed cross-coupling reaction. The characterization results revealed C-O chemical bond formed at the heterointerface between P17-E and Bi2MoO6 after in-situ polycondensation and endowed the hybrids with observably improved photogenerated carries transfer capabilities. Visible, light-driven photocatalytic removal of ciprofloxacin and Cr(VI) were significantly enhanced after the incorporation of P17-E into Bi2MoO6, whether with the morphology of nanosheets, nanobelts, or microspheres. Moreover, these P-BMO hybrids were also found to exhibit excellent sustainable photocatalytic performance after four runs of photocatalytic evaluation tests, suggesting their high activity and stability. To better eliminate the redox ability enhancement of P-BMO, a reasonable Z-scheme electrons transferring mechanism between P17-E and Bi2MoO6 was proposed and proved by the determination of •O2– and •OH and Pt nanoparticles photodeposition experiments. This work might provide a viable source and insight into the design of Z-scheme photocatalysts with excellent redox ability for environmental remediation.

Singly and Doubly Sulfone-Inserted Porphyrin Arch-Tape Dimers

Abstract A singly sulfone-inserted porphyrin arch-tape dimer was synthesized from 2-iodoporphyrin via stepwise transformations consisting of palladium-catalyzed cross-coupling reaction with bis(tributylstannyl) sulfide, tungsten-catalyzed oxidation with hydrogen peroxide, and oxidative fusion with AuCl3 and AgOTf. This new synthetic protocol enabled the synthesis of doubly sulfone-inserted arch-tape dimer as the first example of arch-tape dimer containing two neighboring seven-membered rings. These sulfone-inserted porphyrin arch-tape dimers were fully characterized by X-ray crystal structural analysis, NMR and UV/Vis/NIR absorption spectroscopies, cyclic voltammetry, and theoretical calculations. Furthermore, arch-to-arch inversion dynamics of arch-tape dimers were examined by subjecting newly synthesized mesityl-substituted porphyrin arch tapes to the variable temperature 1H NMR measurements.

Highly Efficient Method for Suzuki Reactions in Aqueous Media.

Herein, we report the crystal structure and characterization of mono-6-(l-aminopropanol)-deoxy-β-cyclodextrin (Ln@β-CD). A highly efficient, in situ generated catalyst, PdCl2(Ln@β-CD), was synthesized for palladium-catalyzed cross-coupling reactions under mild reaction conditions, and the use of this catalyst in Suzuki cross-couplings was investigated. Low palladium loadings of 0.01 mol % PdCl2(Ln@β-CD) (Pd accounted for approximately 8.4% of the catalyst by mass) were found to be highly efficient for Suzuki cross-couplings in water and afforded the corresponding biaryl compounds in excellent yields. The catalyst can be recycled and reused.

Stereocontrolled synthesis of (E)-stilbene derivatives by palladium-catalyzed Suzuki-Miyaura cross-coupling reaction

A general procedure for the stereocontrolled synthesis of (E)-stilbene derivatives by palladium-catalyzed Suzuki-Miyaura cross-coupling reaction of (E)-2-phenylethenylboronic acid pinacol ester with aryl bromides was investigated. (E)-2-Phenylethenylboronic acid pinacol ester was prepared by 9-BBN-catalyzed hydroboration of phenylacetylene with pinacolborane. This reagent undergoes facile palladium-catalyzed cross-coupling with a diverse set of aryl bromides to provide the corresponding (E)-stilbene derivatives in moderate to good yield. The use of the sterically bulky t-Bu3PHBF4 ligand was crucial to the successful coupling of electron-rich and electron-poor aryl bromides. Complete stereochemical retention of the (E)-2-phenylethenylboronic acid pinacol ester alkene geometry was observed in all of the (E)-stilbene derivatives synthesized.

Synthesis of Alkyl Indium Reagents by Using Unactivated Alkyl Chlorides and Their Applications in Palladium-Catalyzed Cross-Coupling Reactions with Aryl Halides.

An efficient method for the preparation of alkyl indium reagents by using unactivated and cheap alkyl chlorides as substrates in the presence of indium and LiI was developed. The thus-formed alkyl indium species effectively underwent palladium-catalyzed cross-coupling reactions with aryl halides with wide functional group tolerance.

More than just a support: Graphene as a solid-state ligand for palladium-catalyzed cross-coupling reactions

While the primary role of supports in catalysis has been to anchor metal particles to prevent sintering, supports can also activate catalytic processes. We report computational and experimental results that provide a fundamental understanding of how a graphene support may activate both oxidative and reductive reaction steps in the catalytic cycle of Suzuki-Miyaura palladium-catalyzed cross-coupling reactions. Theoretical investigations reveal that the high catalytic activity is linked to the ability of a graphene support to act as both an efficient charge donor and acceptor in oxidation and reduction reaction steps. We compare the activation energy and turn over frequency for a series of supported and homogeneous catalysts and find that exposing palladium-graphene to defect inducing microwave radiation results in dramatically lower activation energies and higher turnover frequencies. These results explain why a defected graphene support may catalyze reaction steps that require both charge donation, and charge acceptance.

Synthesis of 4-Aryl Isoquinolinedione Derivatives by a Palladium-Catalyzed Coupling Reaction of Aryl Halides with Isoquinoline-1,3(2 H,4 H)-diones.

The palladium-catalyzed cross-coupling reaction of aryl halides with isoquinoline-1,3(2 H,4 H)-diones for the synthesis of 4-aryl isoquinoline-1,3(2 H,4 H)-diones was developed. The reaction conditions exhibit remarkable compatibility with various aryl halides and isoquinoline-1,3(2 H,4 H)-diones, and the product could be conveniently transformed to 4-aryl tetrahydroisoquinolines. (±) Dichlorofensine was synthesized using this protocol in two steps with an overall yield of 71%.

20-(N-Methylpyridiniumyl)ethynylated chlorophyll-a derivative with an intense Qx absorption band at a green to orange region

Methyl 20-substituted mesopyropheophorbides-a were prepared by the chemical modification of natural chlorophyll-a via palladium-catalyzed cross-coupling reactions. The 20-ethynylation and further 2-pyridylation showed bathochromic shifts in their visible absorption bands as well as hyperchromic effects of the Qx bands in a diluted chloroform solution. The protonation and methylation at the nitrogen atom of the 202-pyridyl group induced much larger shifts and effects, especially giving red-shifted and intensified Qx bands.

Synthesis of bench-stable solid triorganoindium reagents and reactivity in palladium-catalyzed cross-coupling reactions.

Bench-stable solid triorganoindium compounds have been prepared by coordination with 4-(dimethylamino)pyridine (DMAP). The solid R3In(DMAP) complexes are obtained from the corresponding solution of R3In in quantitative yield and can be stored for up to several weeks. These reagents show excellent reactivity in palladium-catalyzed cross-coupling reactions with organic electrophiles.

A direct synthetic method for (nitronyl nitroxide)-substituted π-electronic compounds via a palladium-catalyzed cross-coupling reaction with a zinc complex

We have developed an efficient synthetic method for (nitronyl nitroxide)-substituted π-electronic compounds via palladium-catalyzed cross-coupling reactions with a zinc complex of the parent nitronyl nitroxide radical anion.

Synthesis of Functionalized Triphenodioxazines via Palladium Catalyzed Cross-Coupling Reactions

Synthesis of Functionalized Triphenodioxazines via Palladium Catalyzed Cross-Coupling Reactions

Recent Advance of Palladium-Catalyzed Cross-Coupling Reactions of Organoalanes with Electrophiles Reagents

Recent Advance of Palladium-Catalyzed Cross-Coupling Reactions of Organoalanes with Electrophiles Reagents

Palladium-Catalyzed Cross-Coupling Reaction of Arenesulphonate with Phosphite

Palladium-Catalyzed Cross-Coupling Reaction of Arenesulphonate with Phosphite

Palladium-Catalyzed Cross-Coupling Reactions of Borylated o-Carborane: Synthesis of 3,6-Diaryl-o-carboranes

Palladium-Catalyzed Cross-Coupling Reactions of Borylated <i>o</i>-Carborane: Synthesis of 3,6-Diaryl-<i>o</i>-carboranes