Pd-catalyzed Coupling Reaction Research Articles

Stereodefined Construction of Trisubstituted Alkenes by Direct Coupling Reaction of Allylating Agents, Alkynes, and Organoboranes

Tandem reaction: The Pd-catalyzed three-component coupling reaction of an allylic alcohol, terminal alkyne, and organoborane to give (E)-1-substituted 2-alkyl-1,4-pentadienes, involving geminal allylation and alkylation at the acetylenic terminal carbon, is described. Bis-diene undergoes a similar multicomponent coupling reaction with acetylene and organoborane, involving cyclization of bis-π-allylpalladium, to form trans-allyl pentadienyl cyclic and heterocyclic compounds with excellent regio- and stereoselectivities (see scheme).

Syntheses of Amino Group‐Substituted N‐Confused Porphyrins

AbstractTetraphenyl N‐confused porphyrins (NCTPP) bearing amino substituents were synthesized for the purpose of functionalization toward water‐soluble and biocompatible molecules. The Pd‐catalyzed coupling reaction of 4‐ethynylaniline with the 2‐bromo NCTPP Ag(III) complex yields Pd(II) and Ag(III) coupling products (4a and 4b), at 39% and 55%, respectively. The identities of these products were confirmed by the differences in the isotope patterns of their molecular ion peaks as well as other spectroscopic data. The Ag(III) coupling product, 4b, was demetallated to form the final product, 5, with a yield of 85%. The meso‐tetrakis(4‐nitrophenyl) N‐confused porphyrin, 6, was synthesized through a methanesulfonic acid catalyzed condensation of pyrrole with the 4‐nitrobenzaldehyde with a yield of 6.8%. Reduction of the compound to meso tetrakis(4‐aminophenyl) N‐confused porphyrin, 7, was achieved with a yield of 90%.

Influence of Second Coordination Sphere Hydroxyl Groups on the Reactivity of Copper(I) Complexes

We report the enhanced reactivity of hydroxyl substituted CuN(3)(+) derivatives, where N(3) = tris(picolinyl)methane (tripic) and related derivatives, upon deprotonation of the O-H functionality. The work capitalizes on new methodology for incorporating hydroxyl groups into the second coordination sphere of copper centers. The key synthetic methodology relies on Pd-catalyzed coupling reactions of dilithiated 6-methyl-2-pyridone with bromopyridyl derivatives. These building blocks allow the preparation of tridentate N(3) ligands with OH and OMe substituents flanking the fourth coordination site of a tetrahedral complex. Coupling of these tridendate ligands gives the corresponding hydroxy- and methoxy-functionalized bistripodal ligands. [Cu[bis(2-methylpyrid-6-yl)(2-hydroxypyrid-6-yl)methane](NCMe)](+) ([Cu(2H)(NCMe)](+)) oxidizes readily in air to afford the mixed valence Cu(1.5) dimer ([Cu(2)(2)(2)](+)). Formation of [Cu(2)(2)(2)](+) is accelerated in the presence of base and can be reversed with a combination of decamethylferrocene and acid. The reactivity of [Cu(2H)(NCMe)](+) with dioxygen requires deprotonation of the hydroxyl substituent: neither [Cu(tripic)(NCMe)](+) nor the methoxy-derivatives displayed comparable reactivity. A related mixed valence dimer formed upon oxidation of the dicopper(I) complex of a tetrahydroxy bis(tridentate) ligand, [Cu(2)(6H(4))(NCMe)(2)](2+). The dicopper(I) complex of the analogous tetramethoxy N(6)-ligand, [Cu(2)(5)(NCMe)(2)](2+), instead reversibly binds O(2). Deprotonation of [Cu(2H)(CO)](+) and [Cu(2H)(NCMe)](+) afforded the neutral derivatives Cu(2)(CO) and Cu(2)(2)(2), respectively. The dicopper(I) derivative Cu(2)(2)(2) can be reoxidized, reprotonated, and carbonylated. The silver(I) complex, [Ag(2H)(NCMe)]BF(4), forms an analogous neutral dimer (Ag(2)(2)(2)) upon deprotonation of the hydroxyl group. The structures of ligand 2H, [Cu(2)(5)(NCMe)(2)](+), [Cu(2)(2)(2)](+), [Cu(2)(6H(2))](+), [Ag(2H)(NCMe)]BF(4), and Ag(2)(2)(2) were confirmed by single crystal X-ray diffraction.

Synthesis of Imidazo[4,5-b]pyridines and Imidazo[4,5-b]pyrazines by Palladium Catalyzed Amidation of 2-Chloro-3-amino-heterocycles

A facile synthesis of imidazo[4,5-b]pyridines and -pyrazines is described using a Pd-catalyzed amide coupling reaction. This reaction provides quick access to products with substitution at N1 and C2. A model system relevant to the natural product pentosidine has been demonstrated, as well as the total synthesis of the mutagen 1-Me-5-PhIP.

ChemInform Abstract: Convertible Fluorous Sulfonate Linker for the Synthesis of Diverse Library Scaffolds

AbstractReview: 48 refs.

Pd-catalyzed coupling reaction of acid chlorides with terminal alkynes using 1-(2-pyridylethynyl)-2-(2-thienylethynyl)benzene ligand

In the presence of 1-(2-pyridylethynyl)-2-(2-thienylethynyl)benzene as a ligand, the direct synthesis of alkynones has accomplished by a Pd-catalyzed coupling reaction of acid chlorides with terminal acetylenes under mild conditions.

聚对苯撑乙炔咔唑薄膜对TNT挥发物的检测

Poly(phenylene ethynylene) containing carbazole unit in the main-chain(PPECz) was synthesized by Pd-catalyzed Sonogashira coupling reaction between 3,6-dibromo-9-octylcarbazole and 2,5-dimethoxy-1,4-diethynylbenzene.PPECz in the solution and thin film exhibits obvious luminescence properties,which can be used to detect TNT sensitively.The fluorescence intensity of PPECz thin-film can be quenched 56% by the volatile of 40 μg TNT solid at 60 s at normal atmospheric temperature and pressure.This strategy can provide a platform for developing highly sensitive and efficient chemo sensors for warfare explosives.

Palladium-catalyzed silyl C(sp3)–H bond activation

The first transition-metal-catalyzed activation of silyl C(sp(3))-H bond was realized and synthetically applied. A variety of organic skeletons substituted with SiMe(3) groups could undergo the Pd-catalyzed intramolecular coupling reaction, resulting in an unprecedented synthetic method for yielding six-membered silacycles. It was found that the adjacent Si atom played an essential role for the activation of the C(sp(3))-H bond of the SiMe(3) group; no activation reaction of the C(sp(3))-H bond of the CMe(3) group took place under the same reaction conditions.

Janus dendritic phosphines: synthesis and application in Suzuki coupling reactions

A new kind of codendrimer consisting of a Frechet-type dendron and a Tomalia-type PAMAM dendron has been synthesized via a liquid-phase approach, which could easily be purified using a simple precipitation method without the need for chromatographic separation. Functionalization at the periphery of a PAMAM dendron with bis(diphenylphosphinomethyl)amino groups led to a novel class of Janus dendritic phosphines. Their use as a recyclable homogeneous catalyst has been demonstrated with the Pd-catalyzed Suzuki coupling reaction.

Synthesis of N-alkyl and N-aryl isoquinolones and derivatives via Pd-catalysed C–H activation and cyclization reactions

Relatively less expensive Pd-catalysed oxidative coupling reactions for the preparation of N-alkyl and N-aryl substituted isoquinolones and their derivatives have been developed. A broad reaction scope has been demonstrated. In addition, studies of the reaction additives and mechanistic insights, as well as KIE studies for a better understanding of the reaction pathway, have been discussed.

Pd-Catalyzed Regioselective and Stereospecific Suzuki–Miyaura Coupling of Allylic Carbonates with Arylboronic Acids

The Pd-catalyzed Suzuki-Miyaura coupling reaction of unsymmetric 1,3-disubstituted secondary allylic carbonates with arylboronic acids has been developed in a wet solvent under a base-free system to afford allyl-aryl coupling products in a high level of isolated yields with complete regio- and E/Z-selectivities with good to excellent chemoselectivities. The coupling reaction of optically active allyl carbonates gave allyl-aryl coupling products with excellent enantioselectivities with inversion of the stereochemistry. This coupling method was successfully applied to the synthesis of (S)-naproxen.

Di(1H-benzo[d][1,2,3]triazol-1-yl)methane: An efficient ligand for copper and amine-free palladium-catalysed Sonogashira coupling reaction

An efficient Pd-catalysed Sonogashira coupling reaction was achieved in the absence of copper and amine with inorganic base using phosphene-free, air stable di(1H-benzo[d][1,2,3]triazol-1-yl)methane as ligand. The cross coupling of electron-rich, electron-defficient and hindered aryl halides with terminal alkynes afforded the internal alkynes in good to excellent yields. An efficient Pd-catalysed Sonogashira coupling reaction was achieved in the absence of copper and amine with inorganic base using phosphene-free, air stable di(1H-benzo[d][1,2,3]triazol-1-yl)methane as ligand. The cross coupling of electron-rich, electron-neutral, electron-defficient and hindered aryl halides with terminal alkynes afforded internal arylated alkynes in good to excellent yields.

Synthesis of 2H-indazoles by the [3 + 2] dipolar cycloaddition of sydnones with arynes.

A rapid and efficient synthesis of 2H-indazoles has been developed using a [3 + 2] dipolar cycloaddition of sydnones and arynes. A series of 2H-indazoles have been prepared in good to excellent yields using this protocol, and subsequent Pd-catalyzed coupling reactions can be applied to the halogenated products to generate a structurally diverse library of indazoles.

Heck coupling in the gas phase: Examination of the reaction mechanism by ion/molecule reactions and mass spectrometry

The Heck reaction of isoprene with ( p-iodophenyl)-trimethylammonium iodide was conducted in the gas phase. Relevant species of the catalytic cycle including the ionic product of the Pd-catalyzed coupling reaction were reliably characterized by exact ion mass measurements and by characteristic product ions generated by tandem-MS.

Calcium carbide as a cost-effective starting material for symmetrical diarylethynes via Pd-catalyzed coupling reaction

A convenient and cost-effective synthetic method for symmetrical diarylethynes from inexpensive calcium carbide and aryl iodide has been developed. The reaction not only proceeds with high yield and selectivity but also tolerates a wide range of functional groups. Application of this reaction has enabled the synthesis of highly functionalized oligo (phenyleneethynylenes) to be accomplished.

Novel Reversible Chemosensory Material Based on Conjugated Side-Chain Polymer Containing Fluorescent Pyridyl Receptor Pendants

A novel light-emitting monomer M1 and its side-chain polymer P1 containing three conjugated aromatic pendants, including one pyridyl terminus, were successfully synthesized via Wittig and Pd-catalyzed Heck coupling reactions. The fluorescence of polymer P1 was efficiently quenched upon addition of different metal ions due to the facile energy transfers from the pendent groups of polymer P1 to specific metal ions. Among these metal ions, P1 exhibited extraordinary sensory selectivities for Ni(2+) and Cu(2+) ions over the other metal ions due to the stronger binding capabilities of Ni(2+) and Cu(2+) ions with polymer P1. From the time-resolved fluorescence (TRF) signals in photoluminescence spectra, the emergences of τ(1) decay components in polymer complexes (P1+Ni(2+)) and (P1+Cu(2+)) clearly indicated that their TRF traces consisted of two contributions, one from the complexes (τ(1)) and the other from free polymer P1 (τ(2)). Upon addition of Ni(2+) and Cu(2+) ions, polymer P1 showed faster decay time constants (τ(1)) of metal ion quenching on TRF signals (i.e., better quenching efficiencies on photoluminescence) than its monomer M1. Furthermore, the on-off-on fluorescent switching behavior by adding a tridentate ligand 1,1,4,7,7-pentamethyldiethylenetriamine (PMDTA) to the polymer complex (P1+Cu(2+)) for several successive cycles demonstrated a superior reusable chemosensor of P1 for further applications.

Regioselective Radical Bromoallylation of Allenes Leading to 2-Bromo-Substituted 1,5-Dienes

The regioselective radical bromoallylation of allenes proceeded efficiently in the presence of AIBN as a radical initiator to give 2-bromo-substituted 1,5-dienes in excellent yields. The addition of a bromine radical took place regioselectively onto the central carbon of allenes generating a stable allyl radical, which underwent addition/β-fragmentation reactions with allylbromides. The products could be further functionalized by Pd-catalyzed coupling reactions.

Convertible Fluorous Linker Assisted Synthesis of Tetrasubstituted Furans

Tetrasubstituted furans are prepared by a three-step synthesis including condensation of a fluorous benzaldehyde with an acetophenone followed by Michael-type [3+2] cycloaddition with an 1,3-diketone and Pd-catalyzed coupling reaction for fluorous linker cleavage. The reactions are performed under microwave irradiation and the intermediate purifications are facilitated by fluorous solid-phase extraction (F-SPE).

Cascade Intramolecular N-Arylation/Intermolecular Carboamination Reactions for the Construction of Tricyclic Heterocycles

A new method for the stereoselective synthesis of tetrahydropyrroloindoles and hexahydropyrroloquinolines of general structure 8 is described. These products are formed through cascade Pd-catalyzed coupling reactions between aryl chlorides and unsaturated amine substrates 5. A single catalyst effects an intramolecular N-arylation reaction followed by an intermolecular alkene carboamination reaction to generate two rings, three bonds, and one stereocenter with good chemoselectivity, diastereoselectivity, and chemical yield.

Palladium‐Catalyzed Desulfitative Heck‐Type Reaction of Aryl Sulfinic Acids with Alkenes

An efficient protocol has been developed for the desulfitative Heck-type reaction of aryl sulfinic acids with a variety of alkenes in the presence of a catalytic amount of Pd(OAc)2 and inexpensive Cu(OAc)2 as oxidant. This method does not require a ligand or a base, thereby broadening the scope of Pd-catalyzed coupling reactions.