Search

The first Pd-catalyzed [5 + 2] rollover annulation of 1-benzylpyrazoles with alkynes to assemble 10H-benzo[e]pyrazolo[1,5-a]azepines (tricyclic 2-benzazepines) has been developed. The rollover annulation implies a twofold C–H activation of aryl and heteroaryl Csp2–H bonds (C–H/C–H) of 1-benzylpyrazoles (five-atom partners) and alkynes to give the [5 + 2] annulated compounds. We acknowledge financial support from MICINN (Project PID2020-118048GB-I00 and ORFEO−CINQA Network RED2018-102387-T), the Xunta de Galicia (Project ED431C 2022/27 and Centro Singular de Investigación de Galicia Accreditation 2019−2022, ED431G 2019/03), and the European Union (European Regional Development Fund). A.S.-L. thanks MICINN for a predoctoral contract. SI

Supported 3wt%Pd/α-Al₂O₃ catalyst was tested in selective oxidation of 1,2-propanediol by molecular oxygen. It was found that the catalyst is active in an alkaline water solution. Lactic acid was obtained as the main product of the reaction. Influence of different reaction conditions on 1,2-PDO conversion and oxidation process selectivity was studied. Partial kinetic orders of the reaction with respect to 1,2-propanediol, c0(NaOH), p(O2), n(1,2-PDO)/n(Pd)) were determined and an experimental kinetic model of the catalytic oxidation reaction was obtained. Activation energy of the process was calculated and was found to be about 53 ± 5 kJ/mol.

The stereoselective Suzuki–Miyaura cross-coupling of (Z)-β-enamido triflates is demonstrated. Depending on the nature of the ligand in the palladium catalyst, either retention or inversion of the configuration during the synthesis of β,β-diaryl-substituted enamides is observed. Thus, the method provides synthetic access to both isomers of the target enamides from (Z)-β-enamido triflates.

Synthesis of end-functionalized poly(norbornenes) (PNBs) and poly(ethylidenenorbornenes) (PENBs) were prepared using the palladium catalyst tBu3PPdMeCl/NaBArf in combination with the chain transfer...

Recently developed routes to the synthesis of mono- and polyethynylated azulenes and their transformations into linear oligoazulenes with ethynyl and butadiynyl bridges as well as azulenyl-substituted benzenes, cyclobutadiene complexes, and azulene-substituted tetracyanobutadienes are reviewed. The utility of ethynylazulene derivatives for the synthesis of azulene-substituted heterocycles has also been reviewed.

Herein, the catalytic performance of palladium nanoparticles grafted on the polymeric TSNH2 (Tentagel-S-NH2) resin was investigated for continuous-flow liquid-phase hydrogenation of two industrially relevant chemicals: 2-methyl-3-butyn-2-ol and nitrocyclohexane. We investigated the effect of process parameters such as temperature and pressure on PdTSNH2 activity and selectivity. Depending on the reaction conditions, well-dispersed PdNPs with average size of about 2 nm have shown very high flexibility in terms selectivity toward the desired products: 2-methyl-3-buten-2-ol or 2-methyl-2-butanol in the case of 2-methyl-3-butyn-2-ol hydrogenation and cyclohexanone oxime or cyclohexylamine as the main product in the case of nitrocyclohexane conversion. The optimal reaction conditions for 2-methyl-3-buten-2-ol formation were estimated at 25 °C and 5 bar, and in the case of cyclohexanone oxime formation at 40 °C and 10 bar. We demonstrated the general trend in the catalytic performance of 2.2 wt% Pd grafted on Tentagel-S-NH2. Independently of the hydrogenated substrate, the increase in conversion leads to decreased selectivity to 2-methyl-3-buten-2-ol and cyclohexanone oxime at the expense of increasing the selectivity to 2-methyl-2-butanol or cyclohexylamine. Graphic abstract

A sulfoxantphos modified palladium-catalyzed synthesis of α,β-unsaturated carboxylic acids from alkynes with CO and H2O was described. The atom-economic hydroxycarbonylation of various symmetrical and unsymmetrical alkynes can be achieved with chemo-, stereo-, and regioselectivity, affording the corresponding carboxylic acids in good to excellent yields. Using water as the reaction solvent, the water-soluble palladium catalyst was easily separated from the product and could be reused for 5 cycles.

Ligand-controlled palladium-catalyzed divergent synthesis of isonitriles and nitriles from benzylic carbonates and TMSCN has been developed. The BINAP- or DPEphos-ligated palladium catalyst selectively provides the corresponding benzylic isonitriles, whereas their regioisomers, benzylic nitriles, are formed exclusively under phosphine ligand-free conditions. Mechanistic studies reveal that isonitrile is the primary product under both conditions, but it is isomerized into nitrile in the absence of ancillary phosphine ligands.

A silver‐triggered heterogeneous Pd‐catalyzed oxidative carbonylation has been developed. This heterogeneous process exhibits high efficiency and good recyclability, and was utilized for the one‐pot construction of polycyclic compounds with multiple chiral centers. AgOTf was used to remove chloride ions in the heterogeneous catalyst Pd‐AmP‐CNC, thereby generating highly active PdII, which results in high efficiency of the heterogeneous catalytic system., Silver bullet: A silver‐triggered heterogeneous palladium‐catalyzed oxidative carbonylation of allene amides was developed for the one‐pot construction of pyrrolidones and polycyclic compounds with multiple chiral centers. The heterogeneous catalyst (Pd‐AmP‐CNC) can be recycled at least nine times without loss of activity. The Ag salt removes Cl from Pd‐AmP‐CNC to generate highly active PdII, which results in high efficiency of the heterogeneous catalytic system.

5-Arylidene-1-methyl-2-[2-(methylsulfanyl)-2-phenylethenyl]-1H-imidazol-5(4H)-ones were synthesized as a result of the reaction of 5-arylidene-1-methyl-2-(methylsulfanyl)-1H-imidazol-5(4H)-ones with terminal acetylenes in the presence of a palladium catalyst and copper iodide. This reaction presents a rare example of the formation of a compound with a methylsulfanylethenyl group. A study of the optical properties of the obtained compounds showed that they are characterized by a significant bathochromic shift of spectral maxima in comparison with similar derivatives of the GFP chromophore.

A highly efficient Pd/Ca catalytic system for the directly dehydrative cross-coupling of allylic alcohols with terminal alkynes was developed. This calcium salt cocatalyst facilitates the oxidative addition of the palladium catalyst (1 mol %) to the C-OH bond. Then, the in situ-generated hydroxide ion deprotonates the terminal alkynes to promote the formation of the allylalkynylpalladium intermediate, liberating water as the only byproduct. This proposed mechanism is also supported by density functional theory calculations. An anticancer agent was prepared from inexpensive starting materials on a 10 g scale.

The C–N bond of tertiary amines was activated in the presence of a palladium catalyst and peroxide and subsequently reacted with tertiary amides to provide transamidated products in good yields. The protocol exhibited a broad substrate scope. The optimal conditions were determined as: PdCl2 (2 mol%), KI (10 mol%), NH4Cl (10 mol%) and di-tert-butylperoxide (DTBP), in anisole at 100 °C. N-Benzoylglutarimide, N-phenyl-N-tosylbenzamide, N-Boc-N-phenylbenzamide and benzoyl saccharin were successfully coupled with tertiary amines. The palladium catalyst and DTBP are likely involved in the cleavage of the C–N bond of tertiary amines to provide the corresponding secondary amines.

Recently, we have reported the preparation of a silk fibroin-supported Palladium catalyst (Pd/SF) and its use in the Suzuki-Miyaura cross-coupling of aryl iodides. Since its synthetic applicability and structural features are still far from being fully explored, a deeper investigation is reported here. Pd/SF is tested as a catalyst for the Suzuki-Miyaura and Ullmann coupling reactions of aryl chlorides, in HO/EtOH solvent mixture under atmospheric conditions. Starting from the analysis of the products of the Pd/SF promoted Ullmann reactions of poly-haloarenes, we can hypothesize the existence of catalytic pockets where monoatomic palladium species can form stable complexes with SF. To shed light on this hypothesis, Pd/SF is characterized by Wide-Angle X-ray Scattering (WAXS) analysis, which supports the supposition of catalytic pockets. Finally, using a computational model developed by Molecular Mechanic Energy Minimization we have estimated the dimension of the catalytic pocket of Pd/SF (about 15 Å), in good agreement with the experimental results.

A heterogeneous Janus-type palladium interphase catalyst was obtained by selective surface modification of a hollow mesoporous silica material. The catalyst comprises hydrophobic octyl groups on one side of the silica nanosheets and single-site bis-imidazoline dichlorido palladium(II) complexes on the other. The structure of this composite material has been analyzed by means of elemental analysis, atomic absorption spectroscopy, BET surface analysis, TGA, SEM and solid-state CP-MAS 13C and 29Si NMR spectroscopy. The catalyst showed extraordinary activity for the aqueous-phase oxidation of styrene to acetophenone using 30% hydrogen peroxide as the oxidant. An 88% yield of acetophenone could be achieved after 60 min.

A heterogeneous palladium(II) catalyst anchored to modified metal-organic framework has been synthesized and characterized. The performance of the catalyst has been tested for the hydrogenation of styrene oxide at ambient temperature and pressure. The catalyst showed an excellent activity and selectivity for the preparation of 2-phenylethanol from styrene oxide with 100% conversion and 98% selectivity. The catalyst is very stable and easily recyclable for several times without loss of activity.

Developing new catalytic technologies to utilize biomass as the carbon source of chemical and material industries attracts more attention than ever because of the rapid depletion of fossil feedstoc...

A highly efficient and practical heterogeneous palladium-catalyzed carbonylative coupling of 2-iodoanilines with aryl iodides has been developed. The reaction occurs smoothly in toluene at 110 °C with N,N-diisopropylethylamine as base under carbon monoxide (5 bar) and offers a general and powerful tool for the construction of various valuable 2-arylbenzoxazinones with excellent atom-economy, high functional group tolerance, good to high yields, and easy recyclability of the palladium catalyst. The reaction is the first example of heterogeneous palladium-catalyzed carbonylative coupling for the preparation of diverse 2-arylbenzoxazinones from commercially easily available 2-iodoanilines and aryl iodides.

A chiral bis(imidazolidine)-containing NCN-pincer palladium complex (tBu-PhBidine-Pd-OTf) was an efficient catalyst for the aza-Friedel-Crafts-type reaction of 1H-indoles with isatin-derived N-Cbz-ketimines to give chiral 3-aminobisindole compounds having differently oxidized indole units with high enantioselectivities.

A method for the regioselective reduction of the terminal double bond of 1,1-disubstituted allenes has been developed. In the presence of a palladium catalyst, tetrahydroxydiboron and stoichiometric water, allene semireduction proceeds in high yield to afford Z-alkenes selectively.

2,4-Dichlorophenylacetic acid is synthesized in high yield via the carbonylation of 2,4-dichlorobenzyl chloride, and various experimental conditions are evaluated. Xylene, bistriphenylphosphine palladium dichloride, tetraethylammonium chloride and sodium hydroxide in solution are added to the reaction system and held at 80 °C under a CO atmosphere. 2,4-Dichlorophenylacetic acid is obtained in a maximum yield of 95%, and a mechanism for 2,4-dichlorobenzyl chloride carbonylation is proposed. The reaction system provides a mild, effective and novel means by which to prepare phenylacetic acid derivatives from their corresponding benzyl chloride derivatives.

Dehydrogenative C-H arylations of 1,2,3-triazoles were accomplished with the aid of a reusable palladium catalyst in PEG. The widely applicable oxidative palladium catalysis enabled the synthesis of fully decorated 1,2,3-triazoles with a broad functional-group tolerance and ample substrate scope. The sustainability of the aerobic C-H arylation was reflected by the use of PEG as green reaction medium and demonstrated by recycling studies of the catalyst and the reaction medium.

We developed a method for the synthesis of alkynyl amides via the carbonylation of alkynoic acids and C-N activation of tertiary amines. The reaction of alkynoic acid and tertiary amine with carbon monoxide using a palladium catalyst in the presence of oxygen, KI, and K3PO4, gave the desired alkynyl amides in good yields.

The development of a new, highly efficient, and simple method for masking carbonyl groups as acetals and ketals is described. This methodology relies on the nature of the palladium catalyst to direct the acetalization/ketalization reaction. This new protocol is mild and proceed with a very low catalyst loading at ambient temperatures. The method has been extended to a wide variety of different carbonyl compounds with various steric encumbrances to form the corresponding acetals and ketals in excellent yields.