Preparation of isoindolinones via a palladium-catalyzed diamination

A Pd(II)-catalyzed cyclization using oxidative olefin diamination was developed for the preparation of isoindolinones from ortho-olefinic N-methoxybenzamides. Using the optimized reaction conditions, the desired products were obtained in up to 90% yield using NFSI as the oxidant. This reaction provides an efficient and direct access to isoindolinones with amine functionality, an important drug skeleton.     

Palladium mediated spiroketal synthesis: application to pheromone synthesis

Stereospecific Stille coupling reactions of 2-metallo-dihydropyrans with Z-vinyl iodo alcohols and subsequent cyclisation provides rapid access to 1,7-dioxaspiro[5.5]undecane family of spiroketals.     

Palladium mediated bis- and tris-biaryl Heck coupling for the synthesis of heterocycles

A simple and straightforward palladium mediated ligand free bis- and tris-biaryl coupling on an unactivated phenylbenzyl ether system to produce hitherto unreported heterocyclic compound is described.     

Synthesis of chiral isoindolinones via asymmetric propargylation/lactamization cascade

A Zn-mediated propargylation/lactamization cascade reaction with chiral 2-formylbenzoate derived N-tert-butanesulfinyl imines was realized, which provided a practical and efficient method for the synthesis of chiral isoindolinones. High diastereoselectivities (up to 97:3 dr) and good reaction yields were observed for most examined cases.     

Rhodium catalyzed synthesis of isoindolinones via C-H activation of N-benzoylsulfonamides

An efficient approach to a wide range of isoindolinones, including 3-monosubstituted and 3,3-disubstituted isoindolinones, from the annulation of N-benzoylsulfonamides with olefins and diazoacetate has been developed. The transformation is broadly compatible with both terminal and internal olefins. Moreover, diazoacetate is for the first time incorporated into an amide-directed C-H functionalization reaction. Specifically, the rhodium complex [{RhCl₂Cp*}₂] enables the in situ dimerization of diazoacetate in addition to its role in catalyzing C-H functionalization/cross-coupling.     

Palladium mediated stereospecific synthesis of 3-enynyl substituted thioflavones/flavones

The stereocontrolled synthesis of enynes has been accomplished via a sequential Heck-Sonogashira reaction in a simple synthetic operation. A variety of terminal alkynes were reacted with 3-iodo(thio)flavone in the presence of a palladium catalyst and a copper salt affording a mild and one-pot method for the first synthesis of the corresponding 3-enynyl and/or alkynyl derivatives. The mechanism and scope of the reaction are discussed.     

Palladium mediated cycloisomerization of sugar alkynols: synthesis of cyclic enol-ethers and spiroketals

Functionalized bicyclic enol-ethers and spiroketals are prepared by Pd catalyzed cycloisomerization of 3-C-alkynylfuranosyl derivatives. Cycloisomerization of differently substituted alkyne derivatives revealed a preference for 6-endo-dig cyclization over 5-exo-dig if the substituent is not sufficiently electron withdrawing. The scope of these cycloisomerizations has been further extended by integrating with conjugate addition.     

Palladium catalysed synthesis of cyclic amidines and imidates

The palladium catalysed insertion of isonitriles into aryl bromides carrying pendant amine or alcohol groups on the ortho position affords cyclic amidines or imidates in good yield.     

Palladium and nickel complexes of (P,N)-ligands based on quinolines: Catalytic activity for polymerization and oligomerization

Four (P,N)-ligands (1-4) with different steric and electronic properties were synthesized. They were used to prepare the monocationic palladium complexes [Pd(P,N)(CH₃)(NCCH₃)](PF₆) (9-12). The structures of the newly prepared ligand 3 and the neutral palladium complex [Pd(P,N)(CH₃)Cl] (10) were analysed by X-ray. The catalytic activity of the palladium complexes toward the copolymerization of styrene and ethylene with CO was low or non-existent. The nickel complexes [Ni(P,N)(1-naphthyl)Cl] (13-16), modified with the ligands 1-4, were prepared and their catalytic activity toward ethylene oligomerization was studied. They showed high activity at ambient temperature and low ethylene pressure (1-12 bar) in the presence of MAO.     

Synthesis of isoindolinones: Intramolecular [4+2] cycloaddition/retro [4+2] of pyridone propiolamides

A new synthesis of isoindolinones was discovered during a screening campaign aimed at the development of novel methods for the synthesis of pyridone-EZH2 inhibitor analogues. The reaction proceeds via an intramolecular [4+2] cycloaddition of a pyridone with a tethered propiolamide moiety followed by extrusion of isocyanic acid. The discovery, optimization, and scope of the methodology are described.     

Palladium catalyzed synthesis of mandelate derivatives from arylboronic acids and glyoxylate hemiacetals

NHC-coordinated cyclometalated palladium(II) catalyzed addition of arylboronic acids to methyl 2-hydroxy-2-methoxyacetate gave corresponding various functionalized methyl mandelate derivatives in good yields.     

A novel and highly stereoselective route for the synthesis of non-racemic 3-substituted isoindolin-1-one targets

A new, versatile and highly stereoselective approach for the synthesis of non-racemic 3-substituted isoindolin-1-ones is described from a readily available chiral template. The potential of this new protocol is demonstrated through the synthesis of an enantiomerically enriched 3-alkyl N-H isoindolin-1-one target with an e.e. of 98%.     

Solid-phase synthesis of isoquinolinones using Bischler-Napieralski cyclization

Isoquinolinone is a structural unit found in many natural products having various important biological activities. A traceless solid-phase synthetic approach has been developed to prepare isoquinolinone derivatives. This approach enables one to synthesize isoquinolinones having various moieties on benzene nuclei and also can produce derivatives with a proton on the amide nitrogen.     

Asymmetric synthesis of 3,3-disubstituted isoindolinones

An anionic chiral auxiliary-mediated asymmetric alkylation of carbamate 2 affords 3,3-disubstituted isoindolinones 3 in moderate to high de. The chiral auxiliary can be removed and recovered under mild conditions, and the resulting enantiopure lactams further elaborated.     

Palladium(II) catalyzed carbonylative dimerization of allenyl ketones: efficient synthesis of difuranylketones

Palladium(II) catalyzed carbonylation of 1,2-allenyl ketones 1 in the presence of p-benzoquinone (1 equiv) under a CO atmosphere (balloon) afforded difuranylketones 4 in moderate to good yields. Mechanistically, the electron-withdrawing nature of the acyl group should enhance the electrophilicity of the acylpalladium species B, and thus promote the oxypalladation of an additional molecule of 1, leading to the difuranyl ketone 4.     

Palladium(II) mediated aziridination of olefins with bromamine-T as the nitrogen source: scope and mechanism

The palladium(II)-promoted reaction of a variety of olefins and bromamine-T provided N-tosyl-2-substituted aziridines under mild conditions. Olefins bearing chiral appendages gave only a poor to modest diastereoselectivity. Appropriate deuterated olefins were selected to study the stereochemistry of the reaction. A Pd(IV) intermediate is proposed as the aziridinating species.     

Palladium(II) thiohydrazone complexes: synthesis,spectral characterization and antifungal study

Palladium(II) complexes of type [Pd(L)Cl₂] [where, L?=?benzaldehyde-1,1-diphenyl-2-thiohydrazone (L¹), salicylaldehyde-1,1-diphenyl-2-thiohydrazone (L²), acetaphenone-1,1-diphenyl-2-thiohydrazone (L³) and cyclohexanone-1,1-diphenyl-2-thiohydrazone (L⁴)] have been synthesized. The thiohydrazones can exist as thione-thiol tautomers and coordinate as a bidentate N–S ligand. The ligands are found to be monobasic bidentate. The complexes have been characterized by elemental analysis, IR, mass, electronic, ¹H NMR spectroscopic studies. In vitro antifungal studies against fungi Aspergillus fumigatus, Aspergillus flavus and Aspergillus niger for some complexes have also been carried out.     

Palladium mediated activation of C-F bonds in 2,4,6-trifluoropyrimidine: Synthesis and structure of palladium pyrimidyloxy and pyrimidinone derivatives

[PdMe₂(dcpm)] (1) reacts with 2,4,6-trifluoropyrimidine in the presence of water to give the palladium derivative [PdMe{4-C₄N₂F₂H(O)}(dcpm)] (2). When additional triethylamine is present complex [PdMe(2-OC₄N₂F₂H)(dcpm)] (4) in addition to 2 is formed. Compound 2 converts slowly into the binuclear complex [Pd{4-C₄N₂F₂H(O)}(μ-dcpm)]₂ (5). The molecular structure of 5 was determined by X-ray crystallography. The palladium-palladium distance is 2.5898(3) Å.     

Mixed-Metal Clusters of Palladium

The importance of palladium complexes in catalytic processes is well-demonstrated by its applications in hydrogenation processes in industry. Mixed metal clusters of palladium are of interest as the palladium ion can attain either a 16- or 18-electron configuration which is an important feature for catalytic processes. Recent developments in the preparation, characterization, chemical and physical properties of these clusters are discussed in this review.