Direct Suzuki-Miyaura Research Articles

Synthesis of Finite Molecular Nanotubes by Connecting Axially Functionalized Macrocycles

Synthesis of Finite Molecular Nanotubes by Connecting Axially Functionalized Macrocycles

Synthetic Chemistry with Lewis Acidity‐Diminished B(aam) and B(dan) Groups: Borylation Reactions and Direct Cross‐Couplings

AbstractThis review describes recent advances in the synthesis of anthranilamide/1,8‐diaminonaphthalene‐substituted organoboron compounds with diminished boron Lewis acidity via catalytic B(aam)‐ and B(dan)‐installing borylation reactions, which have attracted growing attention especially in the last five years owing to their unique reactivity, regioselectivity, and the outstanding stability toward air and moisture of organoboron compounds obtained therefrom. Direct Suzuki–Miyaura cross‐couplings with R–B(aam)/B(dan), which were believed to be wholly unreactive until recently, are also discussed.magnified image

Direct Suzuki–Miyaura Coupling with Naphthalene-1,8-diaminato (dan)-Substituted Organoborons

The actually direct Suzuki–Miyaura coupling with “protected” R–B(dan) (dan = naphthalene-1,8-diaminato) was demonstrated to smoothly occur without in situ deprotection of the B(dan) moiety. The use...

Increase of Direct C-C Coupling Reaction Yield by Identifying Structural and Electronic Properties of High-Spin Iron Tetra-azamacrocyclic Complexes.

Macrocyclic ligands have been explored extensively as scaffolds for transition metal catalysts for oxygen and hydrogen atom transfer reactions. C-C reactions facilitated using earth abundant metals bound to macrocyclic ligands have not been well-understood but could be a green alternative to replacing the current expensive and toxic precious metal systems most commonly used for these processes. Therefore, the yields from direct Suzuki-Miyaura C-C coupling of phenylboronic acid and pyrrole to produce 2-phenylpyrrole facilitated by eight high-spin iron complexes ([Fe3+L1(Cl)2]+, [Fe3+L4(Cl)2]+, [Fe2+L5(Cl)]+, [Fe2+L6(Cl)2], [Fe3+L7(Cl)2]+, [Fe3+L8(Cl)2]+, [Fe2+L9(Cl)]+, and [Fe2+L10(Cl)]+) were compared to identify the effect of structural and electronic properties on catalytic efficiency. Specifically, catalyst complexes were compared to evaluate the effect of five properties on catalyst reaction yields: (1) the coordination requirements of the catalyst, (2) redox half-potential of each complex, (3) topological constraint/rigidity, (4) N atom modification(s) increasing oxidative stability of the complex, and (5) geometric parameters. The need for two labile cis-coordination sites was confirmed based on a 42% decrease in catalytic reaction yield observed when complexes containing pentadentate ligands were used in place of complexes with tetradentate ligands. A strong correlation between iron(III/II) redox potential and catalytic reaction yields was also observed, with [Fe2+L6(Cl)2] providing the highest yield (81%, -405 mV). A Lorentzian fitting of redox potential versus yields predicts that these catalysts can undergo more fine-tuning to further increase yields. Interestingly, the remaining properties explored did not show a direct, strong relationship to catalytic reaction yields. Altogether, these results show that modifications to the ligand scaffold using fundamental concepts of inorganic coordination chemistry can be used to control the catalytic activity of macrocyclic iron complexes by controlling redox chemistry of the iron center. Furthermore, the data provide direction for the design of improved catalysts for this reaction and strategies to understand the impact of a ligand scaffold on catalytic activity of other reactions.

Greener Biogenic Approach for the Synthesis of Palladium Nanoparticles Using Papaya Peel: An Eco-Friendly Catalyst for C-C Coupling Reaction.

The development of a green and sustainable synthetic methodology still remains a challenge across the globe. Encouraging the prevailing challenge, herein, we have synthesized Pd nanoparticles (Pd NPs) in a green and environmentally viable route, using the extract of waste papaya peel without the assistance of any reducing agents, high-temperature calcination, and reduction procedures. The biomolecules present in the waste papaya peel extract reduced Pd(II) to nanosize Pd(0) in a one-pot green and sustainable process. As a catalyst, the new Pd NPs offer a simple and efficient methodology in direct Suzuki–Miyaura and Sonogashira coupling with excellent yields under mild reaction conditions.

Pd-PEPPSI: A General Pd-NHC Precatalyst for Suzuki–Miyaura Cross-Coupling of Esters by C–O Cleavage

The Suzuki–Miyaura cross-coupling of aryl esters by selective C–O bond cleavage represents a powerful methodology in organic synthesis. Here, we report that versatile, easily prepared, well-defined Pd-PEPPSI type precatalysts serve as highly reactive catalysts for the direct Suzuki–Miyaura cross-coupling of esters. Sterically and electronically diverse aryl esters couple with arylboronic acids in good to excellent yields using a single, operationally simple protocol. Kinetic studies demonstrate that the cross-coupling of aryl esters proceeds with rates similar to the cross-coupling of amides. This study strongly supports the use of well-defined Pd(II)-NHC precatalysts bearing pyridine “throw-away” ligands for the selective C(acyl) cleavage of bench-stable carboxylic acid derivatives. Considering the modular scaffold of Pd-NHC precatalysts, we envision that the method will be of general interest for the development of new catalysts for C–O cleavage reactions.

Pd-PEPPSI: Pd-NHC Precatalyst for Suzuki–Miyaura Cross-Coupling Reactions of Amides

Pd-PEPPSI-IPr serves as a highly reactive precatalyst in the direct Suzuki-Miyaura cross-coupling of amides. An array of amides can be cross-coupled with a range of arylboronic acids in very good yields using a single, operationally simple protocol. The studies described represent the first use of versatile PEPPSI type of Pd-NHC complexes as catalysts for the cross-coupling of amides by N-C bond activation. The method is user-friendly, since it employs a commercially available, air- and moisture-stable Pd-PEPPSI-IPr complex. Pd-PEPPSI-IPr provides a significant improvement over all current Pd/phosphane catalysts for amide N-C bond activation. Mechanistic studies provide insight into the reaction rates of Pd-NHC-catalyzed cross-coupling of different amides, with Pd-PEPPSI-IPr being particularly effective for the cross-coupling of N-Boc carbamates under the developed conditions.

General Method for the Suzuki–Miyaura Cross-Coupling of Amides Using Commercially Available, Air- and Moisture-Stable Palladium/NHC (NHC =N-Heterocyclic Carbene) Complexes

The direct Suzuki–Miyaura cross-coupling of amides catalyzed by Pd-NHC complexes is reported. Using a single protocol, commercially available, air- and moisture-stable (NHC)Pd(R-allyl)Cl complexes can effect Suzuki–Miyaura cross-coupling of a wide range of amides with arylboronic acids in very good yields. The studies described herein represent the use of versatile Pd-NHC complexes as catalysts for transition-metal-catalyzed cross-coupling of amides by N–C bond activation. The Pd-NHC catalysts provide a significant improvement over all current Pd-PR3 systems employed for the amide N–C bond activation. Mechanistic studies provide strong support for the development of a unified reactivity scale of the amide bond for the generation of acyl-metal intermediates.

Modular Combination of Enzymatic Halogenation of Tryptophan with Suzuki–Miyaura Cross‐Coupling Reactions

AbstractThe combination of the biocatalytic halogenation of l‐tryptophan with subsequent chemocatalytic Suzuki–Miyaura cross‐coupling reactions leads to the modular synthesis of an array of C5, C6, or C7 aryl‐substituted tryptophan derivatives. In a three‐step one‐pot reaction, the bromo substituent is initially incorporated regioselectively by immobilized tryptophan 5‐, 6‐, or 7‐halogenases, respectively, with concomitant cofactor regeneration. The halogenation proceeds in aqueous media at room temperature in the presence of NaBr and O2. After the separation of the biocatalyst by filtration, a Pd catalyst, base, and boronic acid are added to the aryl halide formed in situ to effect direct Suzuki–Miyaura cross‐coupling reactions followed by tert‐butoxycarbonyl (Boc) protection. After a single purification step, different Boc‐protected aryl tryptophan derivatives are obtained that can, for example, be used for peptide or peptidomimetic synthesis.

A short, general, Suzuki–Miyaura coupling anchored approach to 3-alkenylbutenolides: total synthesis of akolactones A & B, hamabiwalactone B and ancepsenolide

An efficient and versatile synthesis of 3-alkenylbutenolides through direct Suzuki–Miyaura cross coupling reaction between preformed 3-halobutenolides and a range of readily accessible boronic acids has been devised. The coupling process exhibits good functional group compatibility and is preparatively viable. The methodology has been applied to achieve short syntheses of natural products rac-akolactones A & B and rac-hamabiwalactone B. The scope of the Suzuki–Miyaura reaction based protocol has been further amplified through the synthesis of 3,3′-alkenyl-bis-butenolides by employing α, ω-bis-boronic acids as coupling partners and applied to a synthesis of bioactive natural product rac-ancepsenolide.

Development of the Direct Suzuki–Miyaura Cross-Coupling of Primary B-Alkyl MIDA-boronates and Aryl Bromides

The development of a palladium-catalyzed sp(3)-sp(2) Suzuki-Miyaura cross-coupling of B-alkyl-N-methyliminodiacetyl (B-alkyl MIDA) boronates and (hetero)aryl bromides is reported. This transformation is tolerant of a variety of functional groups (F, NO2, CN, Cl, COCH3, and CHO). B-Alkyl MIDA boronates allow an efficient cross-coupling reaction directed toward the synthesis of unsymmetrical methylene diaryls as well as alkylated arenes in good to excellent yields.

Iron-Catalyzed Direct Suzuki–Miyaura Reaction: Theoretical and Experimental Studies on the Mechanism and the Regioselectivity

The mechanism of the Suzuki–Miyaura cross-coupling reaction between pyridine and phenylboronic acid catalyzed by the complex of iron salt combined with macrocyclic polyamine (iron–MCPA) was investigated theoretically and experimentally. It was found that the overall reaction includes three steps: C–H activation, transmetalation, and reductive elimination. The results indicate that the rate-determining step is the transmetalation step. The C–H activation of a different position on pyridine is the origin of the regioselectivity. The transmetalation step is the regio-determining step. Both the C–H activation and the transmetalation steps favor the regioselective formation of the ortho product. The oxoiron complex is predicted to be the active species theoretically and is confirmed by experiments. The calculations correctly reproduce the major product, 2-phenylpyridine, which is consistent with the experimental observation.

ChemInform Abstract: Mutual Activation: Suzuki—Miyaura Coupling Through Direct Cleavage of the sp2 C—O Bond of Naphtholate.

AbstractKey step of the direct Suzuki—Miyaura coupling of naphthols with various aryl boroxines is the in situ generation of borates offering a new concept of mutual activation of the coupling partners.

Direct Suzuki-Miyaura Coupling of Phenol Derivatives via Mutual Activation

Direct Suzuki-Miyaura Coupling of Phenol Derivatives via Mutual Activation

ChemInform Abstract: Iron‐Mediated Direct Suzuki—Miyaura Reaction: A New Method for the ortho‐Arylation of Pyrrole and Pyridine.

AbstractThe first example of the iron‐catalyzed direct Suzuki—Miyaura reaction between N‐heterocyclic compounds and arylboronic acids is presented.

Microwave-promoted Suzuki–Miyaura coupling of arylboronic acids with 1-bromo-2-naphthol, o-bromophenol, and o-chlorophenol

In this letter we report a simple and efficient way for the direct Suzuki–Miyaura cross-coupling of unprotected 2-hydroxyaryl bromides and of 2-chlorophenol with arylboronic acids using suitable phosphine/Pd(OAc) 2 catalysts systems with moist K 3PO 4/toluene or moist CsF/dioxane and microwave heating (20 min 105 °C to 3 h 100–120 °C) with an internal temperature control providing 2-hydroxybiaryls in yields up to 98%.

Carbonylative and direct Suzuki–Miyaura cross-coupling reactions with 1-iodo-cyclohexene

The Suzuki–Miyaura reaction of 1-iodo-cyclohexene and phenylboronic acid (or 3-trifluoromethoxy-phenylboronic acid) was investigated concerning the detailed analyses of the catalytic mixtures. The reaction was carried out both under argon (‘direct’ Suzuki–Miyaura coupling) and carbon monoxide (‘carbonylative’ Suzuki–Miyaura reaction). Palladium(II) acetate based in situ formed palladium(0) catalysts were used as catalytic system. The detailed analysis revealed the importance of the formation of the Heck-products and the homo-coupling of the substrate. The corresponding alkenyl-aryl-ketone was obtained by carbon monoxide insertion into palladium(II)-aryl bond.