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The area of combining an enzyme and transition metals to catalyse the sequence of reactions in one-pot which improve total conversion and operational stability has seen tremendous growth in recent years. Herein, we describe the synthesis and substrate controlled modification of β-aminocarbonyl using α-amylase enzyme and Pd-based catalyst in the one-pot. Moreover, the chemo-enzymatic approach provides substituted indole derivatives unprecedentedly when isocyanide was used in the reaction. In the second phase, isocyanide was replaced by phenyl boronic acid which in turn provides the substituted amino biaryls in good yield. Next, the feasibility of one-pot chemo-enzymatic approach was proved by employing substituted 2-bromo aniline along with different isocyanide/phenyl boronic acid and obtained the corresponding products in 56–84% isolated yield. [ABSTRACT FROM AUTHOR]

This study aimed to assess the efficacy of a bimetallic system consisting of Mg0 -Pd0 and the bacterium Acinetobacter sp. for the complete detoxification of lindane. Our results demonstrate that palladium immobilized on activated charcoal achieved a removal rate of >99% for 100 mg.L-1 of Lindane within 10 minutes, with the accumulation of trace amounts of intermediates. The reductive transformation of lindane followed 1st-order kinetics, with a calculated rate constant (kobs) of 0.77 min-1. The bimetallic system resulted in the formation of a non-toxic hydrocarbon as the end-product, indicating complete dehalogenation of lindane. Furthermore, Acinetobacter sp. effectively mineralized >98% of 100 mg.L-1 of Lindane after 26 h of cultivation without any accumulation of toxic metabolite(s) in the reaction medium, demonstrating the efficiency of the biological system. Integrating both chemical and biological systems could provide significant advantages for the treatment of lindane, reducing the treatment time and overall cost. This synergistic approach can significantly enhance the overall removal efficiency of lindane from contaminated soil and water. [ABSTRACT FROM AUTHOR]

Herein, a straightforward method for the construction of tetrazole derivatives has been achieved through Pd‐catalyzed isocyanide insertion reactions, which is a good extension for the response of multi‐molecule isocyanides. The Ugi‐N3 reaction was introduced to the transformation to enrich the diversity of skeleton structures. The commercially available starting materials and moderate to good yields make this method a valuable tool for generating N‐containing heterocyclic compounds. [ABSTRACT FROM AUTHOR]

[Display omitted] • PNS ligand integration in synthesized Pd(IΙ), Pt(IΙ) and novel Hg(IΙ) complexes. • The synthesized compounds are investigated using infrared and multinuclear NMR spectroscopy (1H, 13C, 31P NMR). • Three compounds' crystal structures were identified. • The Suzuki cross-coupling reaction's pre-catalyst function for Pd(IΙ) complex was investigated. The reaction of monooxidized thioyl (4-CH 3)C 6 H 3 N-2-NH(P(S)Ph 2) (1) ligand with MCl 2 (COD)(M = Pd, Pt) in equimolar ratio resulted in cis -[MCl 2 { 1 -κ2 S,Npy }] (M = Pd (2), Pt(3)) complexes. Also, The reaction of 1 with HgX 2 (X = Cl, I) produced cis -[HgX 2 { 1 -κ2 S,Npy }] (X = Cl(4), I(5)). Complexes 2 – 5 have been isolated and characterized by multinuclear NMR (1H, 13C, and 31P) and IR spectroscopy. The molecular structures of 2 , 4 , and 5 were determined using single X-ray crystallography. 4 and 5 are the first structurally defined instances of this type of κ2 S,Npy -bidentate ligand with Hg(II) metal complexes. The new palladium(II) complex 2 as a pre-catalyst in the Suzuki cross-coupling process was also investigated. [ABSTRACT FROM AUTHOR]

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• N -unsubstituted 1,2-benzothiazine 1,1-dioxides were explored against Mtb CM. • Their sonochemical synthesis involved Pd–catalyzed one-pot coupling-cyclization. • In silico studies indicated 3d, 3e and 3f as molecules of potential interest. • They formed H-bonds with GLU68, SER70 and GLY71 residues of Mtb CM. • In silico prediction indicated a good overall ADME for 3a, 3b and 3n. The Pd-catalyzed one-pot sonochemical synthesis followed by in silico and in vitro evaluation of a range of N -unsubstituted 1,2-benzothiazine 1,1-dioxide derivatives is reported. The synthesis involved ultrasound assisted coupling-cyclization of 2-iodobenzenesulfonamide with terminal alkynes in the presence of (PPh 3) 4 Pd, CuI, ZnCl 2 and Et 3 N to afford the expected products in 73-80 % yield. This is the first example of accessing N -unsubstituted 1,2-benzothiazine 1,1-dioxides via Pd-catalyzed coupling-cyclization strategy in a single pot. Moreover, the use of mild conditions and ultrasound as the source of green energy are the main features of this approach. In silico studies suggested that all the synthesized compounds interacted with the loop near the active site of Mtb chorismate mutase or Mtb CM. Indeed, these compounds showed H-bonding with residues in the hinge region of the active site loop and the benzothiazine 1,1-dioxide moiety was responsible for H-bonding with GLU68, SER70 and GLY71 residues. Three compounds e.g. 3d, 3e and 3f interacted well with Mtb CM via the aforementioned H-bonds and their orientations seemed to be influenced considerably by the effective non-H-bond interactions with LEU65 and PRO66. They also showed encouraging (54-62 %) inhibition of Mtb CM in vitro when tested at 10 µM. The outcome of in silico and in vitro studies along with the ADME predictions identified compound 3c, 3d and 3e as pre-hits for further pharmacological study. N -Unsubstituted 1,2-benzothiazine 1,1-dioxides accessed via the transition metal catalyzed one-pot sonochemical approach were explored against Mtb CM in silico and in vitro [Display omitted] [ABSTRACT FROM AUTHOR]

Pd nanospecies supported on porous g-C3N4 nanosheets were prepared for efficient reductive amination reactions. The structures of the catalysts were characterized via FTIR, XRD, XPS, SEM, TEM, and TG analysis, and the mechanisms were investigated using in situ ATR–FTIR spectroscopic analysis complemented by theoretical calculation. It transpired that the valence state of the Pd is not the dominating factor; rather, the hydroxyl group of the Pd(OH)2 cluster is crucial. Thus, by passing protons between different molecules, the hydroxyl group facilitates both the generation of the imine intermediate and the reduction of the C=N unit. As a result, the sterically hindered amines can be obtained at high selectivity (>90%) at room temperature.

The catalytic cyclopropanation of spiro[2.4]hepta‐4,6‐diene and 1,1,2,2‐tetradeutero‐, 1‐methyl‐, and 1,1‐dimethylspiro[2.4]hepta‐4,6‐dienes on treatment with excess diazomethane in the presence of palladium catalysts, which gives products of double bond dicyclopropanation, is also accompanied by an unusual transformation of the three‐membered ring of the spiro moiety with elimination of the unsubstituted methylene group in the form of ethylene to give the corresponding 5‐methylidenetricyclo[4.1.0.02,4]heptanes (bishomofulvenes). The putative mechanism of the reactions is considered. [ABSTRACT FROM AUTHOR]

A recyclable and non‐phosphine solid palladium (II) catalyst was prepared and characterized by HR‐MS, FT‐IR, XPS, EDS, TGA, SEM, TEM and ICP. The Pd‐catalyst exhibited high‐performance catalytic activity in Suzuki and Heck C‐C coupling reactions in an environmentally benign water medium. Further, the Pd‐catalyst (Z4) can be reused for 15 times with little decrease of activity through simple and efficient recovery. In addition, the turn‐over number (TON) of Pd‐ catalyst can reach 380 at room temperature. These results proved that the Pd‐catalyst has a stable structure and can be recycled many times, making the process sustainable. [ABSTRACT FROM AUTHOR]

An alternative method for the preparation of 2′-bromo- (5b) and 2′-iodo- (5c) 1′,2′-unsaturated uracil nucleosides has been developed. The protocol was on the basis of the syn-elimination of pivalic acid from 2′-bromo-(7a,b) and 2′-iodo-(9a,b) 1′-pivaloyloxy-2′-deoxyuridine derivatives, which were derived from the halo-pivaloyloxylation of 3′,5′-bis-O-TBDMS-1′,2′-unsaturated uridine 1. Compounds 5b and 5c were shown to serve as versatile synthons for the respective 2′-C-branched 1′,2′-unsaturated uracil nucleosides, through palladium-catalyzed cross-coupling or halogen-lithium exchange reactions. [ABSTRACT FROM AUTHOR]

The ZSM-5, g-Al2O3, SiO2 and MgO supported Pd-catalysts were prepared for the phenol hydrogenation to cyclohexanone in liquid-phase. The natures of these catalysts were characterized by XRD, N2 adsorption-desorption analysis, H2-TPR, CO2-TPD and NH3-TPD. The catalytic performance of the supported Pd-catalyst for phenol hydrogenation to cyclohexanone is closely related to nature of the support and the size of Pd nanoparticles. The Pd/MgO catalyst which possesses higher basicity shows higher cyclohexanone selectivity, but lower phenol conversion owing to the lower specific surface area. The Pd/SiO2 catalyst prepared by precipitation gives higher cyclohexanone selectivity and phenol conversion, due to the moderate amount of Lewis acidic sites, and the smaller size and higher dispersion of Pd nanoparticles on the surface. Under the reaction temperature of 135 oC and H2 pressure of 1 MPa, after reacting for 3.5 h, the phenol conversion of 71.62% and the cyclohexanone selectivity of 90.77% can be obtained over 0.5 wt% Pd/SiO2 catalyst. Copyright © 2016 BCREC GROUP. All rights reserved Received: 7th March 2016; Revised: 13rd May 2016; Accepted: 7th June 2016 How to Cite: Fan, L., Zhang, L., Shen, Y., Liu, D., Wahab, N., Hasan, M.M. (2016). Liquid-phase Hydrogenation of Phenol to Cyclohexanone over Supported Palladium Catalysts. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (3): 354-362 (doi: 10.9767/bcrec.11.3.575.354-362) Permalink/DOI: http://doi.org/10.9767/bcrec.11.3.575.354-362

The Hirao reaction involving the phosphinoylation or phosphonation of aryl halides by >P(O)H reagents is a P–C bond forming transformation belonging to the recently very hot topic of cross-couplings. The Pd- or Ni-catalyzed variations take place via the usual cycle including oxidative addition, ligand exchange, and reductive elimination. However, according to the literature, the nature of the transition metal catalysts is not unambiguous. In this feature article, the catalysts described for the Pd(OAc)2-promoted cases are summarized, and it is concluded that the “(HOY2P)2Pd(0)” species (Y = aryl, alkoxy) is the real catalyst. In our model, the excess of the >P(O)H reagent served as the P-ligand. During the less studied Ni(II)-catalyzed instances the “(HOY2P)(−OY2P)Ni(II)Cl−” form was found to enter the catalytic cycle. The newest conclusions involving the exact structure of the catalysts, and the mechanism for their formation explored by us were supported by our earlier experimental data and theoretical calculations.

An effect of Pt addition to improve the catalytic performance of Pd-modified Mn-hexaaluminate in the high-temperature oxidation of methane, especially in SO 2 and water presence, has been studied. X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry and differential thermal analysis were used for the characterization of fresh and spent catalysts. Temperature-programmed reduction by hydrogen was employed to study the redox properties of the catalysts. Four high-temperature tests (at 670 °C) of the methane oxidation were applied to reveal the water and sulfur resistance of the catalysts: 1) dry methane-air feed; 2) wet methane-air feed containing 3 wt% of water vapor; 3) methane-air feed containing 1000 ppm of SO 2 ; and 4) wet methane-air feed with 1000 ppm of SO 2 . The Pt-doped Pd-Mn-hexaaluminate catalyst with the atomic ratio of Pt/Pd < 0.3 has been shown to possess the highest catalytic activity in the oxidation of methane, high water and sulfur tolerance, and reducibility by hydrogen as compared to the monometallic Pd-Mn-hexaaluminate catalyst and the bimetallic catalysts with Pt/Pd > 0.5. From the formal kinetic data of the oxidation of methane on the fresh and deactivated catalysts, we assumed that deactivation of the catalysts is due to a decrease in the amount of catalytically active sites in the bimetallic 0.33Pt-0.67Pd(0.27)/MnLaAl 11 O 19 catalyst and a change in the state of active component in the other catalysts. Their oxidation ability and redox behavior were shown to be associated with the highly dispersed PdO particles, a PdO layer (3–5 nm) covering the metal palladium particles as well as the Mn 3+ -enriched MnLaAl 11 O 19 . The improved water and sulfur resistance is found to correlate with the presence of particles of PtPd alloy, with its fraction not exceeding 50%. [ABSTRACT FROM AUTHOR]

The palladium-incorporated catalyst, (0.5% Pd/C) (nanospace engineering KOH-activated carbon material) catalyst with macro-structured carbon nanofibers aggregates and micro-nano-porous activated carbons, has been studied as a candidate for hydro-purification of crude terephthalic acid containing of 4- carboxybenzaldehyde (4-CBA) as an impurity. The efficiency of different carbon structures (macro/micro) was investigated over selectivity catalyst. The reaction products were analyzed by HPLC to determine the amounts of 4-CBA, benzoic acid (BA), 4-Hydroxymethyl benzoic acid (4-HMBA) and para-toluic acid (p-tol). It has been confirmed that 0.5% Pd/microporous catalyst gave an excellent performance to catalyze the hydrogenation of 4-CBA to para-toluic acid due to high micro-porous surface area and the most desirable selectivity to 4-HMBA was obtained with macro-structured carbon nanofibers. Pd/AC catalyst with more micro surface area (85.26%) achieved a maximum yield to the intermediate product of 4-HMBA only 30% whereas the macro-structured CNFs achieved typically 66%. The desired selectivity to para-toluic acid was found to be deep dependent on the micro-porous structure. [ABSTRACT FROM AUTHOR]

Some novel β-biarylacryl ferrocene derivatives were synthesized viaPd-catalytic Suzuki cross-coupling reactions of β-(2-bromophenyl)acrylferroceneand arylboronic acids. The structures were determined with elemental analyses, IRspectra, and 1H-NMR spectra.

The Heck reaction of aryl bromide with a terminal alkene substrate having a chiral center at the allylic position and a phenyl substituent at another terminal carbon is reported. An alkene migration to the phenyl-substituted end carbon is observed, along with the typical Heck reaction. This zipper-type migration occurs through multiple internal carbon bonds, and the stereochemistry of the internal chiral center is completely retained during this process. [ABSTRACT FROM AUTHOR]

An efficient total synthesis toward spiroketal diastereomers of cephalosporolides H and I was achieved, respectively, taking advantage of intramolecular Wacker-type spiroketalization on the common olefin-containing dihydroxy-γ-lactone substrate. By comparing the physical data of natural products with synthetic samples, we suggest that the reported stereochemical assignments for cephalosporolides H and I are incorrect. Our work suggests that the stereochemistry on C-6 of the core spiroketal skeleton should be revised to S from its original R assignment, and the real structures of these natural compounds should be reconsidered. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rosuvastatin based azaindole framework was designed to identify cytotoxic agents. • Sonochemical synthesis of target compounds involved coupling–cyclization strategy. • Several compounds showed significant cytotoxic effects on three cancer cell lines. • 5b inhibited Akt1 in vitro that was supported by its strong interaction with Akt1 in silico. • 5b is a potent inhibitor (MIA Paca-2 IC50 ∼ 19 nM) with NOAEL > 100 μM in Zebrafish. Addressing the increasing incidences of cancer worldwide along with the multifaceted problem of drug resistance via development of new anticancer agents has become an essential goal. Due to the known cytotoxic effects and reported Akt inhibitory potential of azaindoles we designed a new framework incorporating the structural features of rosuvastatin and 5- or 7-azaindole. The framework was used to construct a library of small molecules for further pharmacological evaluation. The design was supported by the docking studies of two representative molecules in silico. A one-pot sonochemical approach was established for the synthesis of these rosuvastatin based azaindoles that involved the coupling–cyclization of a rosuvastatin derived terminal alkyne with appropriate 3-iodopyridine derivatives under Pd/Cu-catalysis. When tested using an MTT assay, some of the synthesized compounds showed desirable cytotoxic effects against three cancer cell lines e.g. HCT 116, Hep G2 and PA-1 but no significant effects against the non-cancerous HEK cell line. According to the SAR the 5-azaindole ring appeared to be marginally better than the 7-azaindole whereas the activity was varied with the variation of sulfonamide moiety attached to the N-1 atom of the azaindole ring. Among all the groups present in the sulfonamide moiety the p -MeC 6 H 4 group appeared to be most effective in terms of activity. While 3b and 5b were identified as initial hit molecules the compound 5b (in addition to 3b) also showed significant inhibition of Akt1 in vitro that was reflected by its strong interaction with Akt1 in silico (with the docking score −11.7 kcal/mol) involving two H-bonding interactions with Ser7 and Asp439 residues. Further, a reasonable ADME was predicted for 5b in silico. Being a potent inhibitor (MIA Paca-2 IC 50 = 18.79 ± 0.17 nM) and with NOAEL (No Observed Adverse Effect Level) > 100 µM in Zebrafish, 5b emerged as a promising compound. [ABSTRACT FROM AUTHOR]

Highlights: [•] Pd promoted sulfated zirconia catalyst Pd–SZ was prepared after proprietary procedure. [•] Catalytic properties were studied in n-butane isomerization upon parameters variation. [•] At low H2/C4 ratios catalyst shows high conversion and selectivity performance. [•] Catalytic stability was unchanged during 90h resource test exposed to 20ppm H2O. [•] n-Butane isomerization technology may be simplified by making use Pd–SZ catalyst. [ABSTRACT FROM AUTHOR]

Pd nanospecies supported on porous g-C3N4 nanosheets were prepared for efficient reductive amination reactions. The structures of the catalysts were characterized via FTIR, XRD, XPS, SEM, TEM, and TG analysis, and the mechanisms were investigated using in situ ATR−FTIR spectroscopic analysis complemented by theoretical calculation. It transpired that the valence state of the Pd is not the dominating factor; rather, the hydroxyl group of the Pd(OH)2 cluster is crucial. Thus, by passing protons between different molecules, the hydroxyl group facilitates both the generation of the imine intermediate and the reduction of the C=N unit. As a result, the sterically hindered amines can be obtained at high selectivity (>90%) at room temperature.

A synergetic effect in the methane oxidation activity of palladium and manganese hexaaluminate was studied over Pd-modified manganese-hexaaluminate catalysts, prepared by incipient wetness impregnation and calcined at 1,200 °C. The magnitude of the synergetic effect is found to be depends on the palladium precursor: it is higher for palladium nitrate and palladium acetate than for tetrachloropalladic acid. The Pd/MnLaAlO catalysts were characterized by X-ray diffraction, X-ray microanalysis, transmission electron microscope and temperature-programmed reduction with hydrogen. These data were compared with the properties of Pd/AlO catalysts. At variation of Pd-precursors, a minor trend to the decrease of the Pd particle size was observed at transition from the ex-chloride Pd/MnLaAlO catalyst with uniform Pd-distribution profile to the ex-nitrate and ex-acetate catalysts with egg-shell Pd-distribution. Slightly smaller size of metal palladium particles in the ex-nitrate and ex-acetate catalysts leads to the formation of larger amount of PdO dispersed on their surface during oxygen-pretreatment in H-TPR experiments (Pd/PdO atomic ratio was 1/4) and under methane-oxidation mixture in comparison with ex-chloride catalysts (Pd/PdO = 4/1). The palladium addition to manganese-hexaaluminate changes strongly its redox properties, as result Mn reduction to Mn take place about 100 °C below that of pure hexaalunimate. The latter indicate probably on the higher oxygen mobility in Pd-modified manganese-hexaaluminate. A higher PdO/Pd ratio formed in the ex-nitrate and ex-acetate Pd-modified manganese-hexaaluminate catalysts together with the high oxygen mobility provide the synergetic effect in methane oxidation activity at light-off temperature region. The high catalytic activity of manganese-hexaaluminate ensures methane combustion efficiency of the Pd-modified manganese-hexaaluminate catalysts at temperature above 700 °C. [ABSTRACT FROM AUTHOR]

We present the results from pilot tests and the industrial use of crusted 0.2% Pd/γ-AlO APKGS-20Sh catalyst for the purification of aerial effluents at OAO Voronezhsintezkauchuk. The stable operation of the catalyst (the degree of purification of ventilation effluents) was observed under real operational conditions that differ appreciably from those specified by the technical regulations in inlet concentrations and hourly space velocities. The hourly space velocity of gas periodically exceeds its normative value by eight times (10000 and 80000 h, respectively). The inlet concentrations of toluene and Nefras incidentally exceed the recommended norms by a factor of more than two. Despite periodic increases in the concentrations of major pollutants above the statutory norms, the outlet concentrations of the catalytic reactor were not observed to exceed their regulatory values. The first batch of APKGS-20Sh catalyst loaded in 2009 has already been in operation for one and a half years. The catalyst can be recommended for use in units for the purification of ventilation effluents at plants producing synthetic rubbers. [ABSTRACT FROM AUTHOR]

Abstract: A new efficient synthesis of aromatic six-membered ring sultones by the implementation of ligand-free Pd-catalyzed intramolecular cyclization of aromatic sulfonates derived from various bromo phenols and naphthols is described. [Copyright &y& Elsevier]

Abstract: A concise and efficient method for the preparation of oxocine derivatives is described via sequential Wittig and intramolecular Heck reactions. The method is highly regioselective and affords high yields of the products. [Copyright &y& Elsevier]

Hydrogenation of sunflower and canola oils over a novel Pd-supported catalyst (pore size of 6.8 nm and BET specific surface area of 837 m2/g) was investigated and compared to commercial nickel catalyst. The formulated catalyst with Pd-loading of 1 wt%, supported on structured silica material was active and selective for the hydrogenation of sunflower and canola oils under mild process conditions. For both oils, the novel Pd supported catalyst exhibited a better selectivity than commercial Ni catalyst at a similar activity with a lower metal loading. For the same iodine value (IV) reduction, the Pd-catalyst produced less saturated fatty acids (SFA) and about the same level of trans fatty acids (TFA), but was more selective towards cis monoenes formation than Ni-catalyst. More importantly, this catalyst produced a reduced level of stearic acid, which at increased levels causes waxy mouth feel of the hydrogenated fat. [ABSTRACT FROM AUTHOR]

Abstract: An original synthetic route toward dibenzo[b,e][1,4]diazepin-11-ones and analogues pyridobenzodiazepinones has been developed. The method relies upon an intramolecular amination process between an (hetero)aryl halide and the appropriate aniline moiety. [Copyright &y& Elsevier]

Pd-catalyzed coupling of O-methylbenzamidoximes gave N-aryl O-methylbenzamidoximes using aryl halides with electron attracting or moderate electron donating groups. Under the same conditions, benzamidoxime failed to undergo coupling and O-acetylbenzamidoxime underwent cyclization to form the corresponding [1,2,4]oxadiazole. [Copyright &y& Elsevier]

While anti-inflammatory properties of isocoumarins are known their PDE4 inhibitory potential was not explored previously. In our effort the non-PDE4 inhibitor isocoumarins were transformed into the promising inhibitors via introducing an aminosulfonyl/aminocarboxamide moiety to the C-3 benzene ring attached to the isocoumarin framework. This new class of isocoumarins were synthesized via a PdCl 2 -catalyzed construction of the 4-allyl substituted 3-aryl isocoumarin ring starting from the appropriate 2-alkynyl benzamide derivative. Several compounds showed good inhibition of PDE4B in vitro and the SAR indicated superiority of aminosulfonamide moiety over aminocarboxamide in terms of PDE4B inhibition. Two compounds 3q and 3u with PDE4B IC 50 = 0.43 ± 0.11 and 0.54 ± 0.19 μM and ≥ 2-fold selectivity over PDE4D emerged as initial hits. The participation of aminosulfonamide moiety in PDE4B inhibition and the reason for selectivity though moderate shown by 3q and 3u was revealed by the in silico docking studies. In view of potential usefulness of moderately selective PDE4B inhibitors the compound 3u (that showed PDE4 selectivity over other PDEs) was further evaluated in adjuvant induced arthritic rats. At an intraperitoneal dose of 30 mg/kg the compound showed a significant reduction in paw swelling (in a dose dependent manner), inflammation and pannus formation (in the knee joints) as well as pro-inflammatory gene expression/mRNA levels and increase in body weight. Moreover, besides its TNF-α inhibition and no significant toxicity in an MTT assay the compound did not show any adverse effects in a thorough toxicity studies e.g. teratogenicity, hepatotoxicity, cardiotoxicity and apoptosis in zebrafish. Thus, the isocoumarin 3u emerged as a new, safe and moderately selective PDE4B inhibitor could be useful for inflammatory diseases possibly including COVID-19. [Display omitted] • Isocoumarins were explored for the first time as a new class of PDE4 inhibitors. • Synthesis involved PdCl 2 -catalyzed construction of the 4-allyl substituted 3-aryl isocoumarin ring. • Compound 3u (PDE4B IC 50 ∼ 0.54 μM) reduced paw swelling, inflammation and pannus formation. • 3u also reduced pro-inflammatory gene expression/mRNA levels and showed good safety in Zebrafish. • 3u is a potential agent for inflammatory diseases. [ABSTRACT FROM AUTHOR]

• A magnetically recoverable heterogeneous catalyst Fe 3 O 4 @SiO 2 @NHC^SPh-Pd(II). • Fe 3 O 4 @SiO 2 @NHC^SPh-Pd(II) catalyzed cross couplings reactions at mild conditions. • Cu and amine free Sonogashira cross coupling of aryl/heteroarylbromides and acetylenes. • Fe 3 O 4 @SiO 2 @NHC^SPh-Pd(II) catalyzed Stille coupling of arylbromides/chlorides and trialkylstannanes. Two value added C C cross coupling reactions; Sonogashira and Stille couplings were achieved at milder conditions in the catalytic presence of a magnetically recoverable heterogeneous catalyst Fe 3 O 4 @SiO 2 @NHC^SPh-Pd(II). The catalyst was earlier reported for Suzuki-Miyaura reaction, and as an extension of its catalytic efficiency, the Stille and Sonogashira cross coupling reactions under aerobic condition has been explored in present report. The Sonogashira coupling of aryl bromides and terminal alkynes produced an excellent yield (~96% at 0.25 mol% Pd) of the desired coupling product under copper and amines free conditions. Moreover, an excellent Stille coupling of readily available and more latent aryl chlorides and trialkylstannane was obtained (yields up to 95% at 0.25 mol% Pd) in absence of toxic fluorides additives. The broad substrate scope of the catalyst for both the coupling reactions and the magnetically recoverable feature of catalyst make this reaction highly desirable for industrial applications of present heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Abstract: Acyclic Pd–diaminocarbene complex showed high catalytic activity in Suzuki arylation of meso-chlorine-substituted tricarboindocyanine dyes. Arylated dyes were obtained in 57–83% yields in the presence of 5×10−4 equiv of catalyst. [Copyright &y& Elsevier]

Facile polymerization reaction conditions were developed for synthesizing conjugated polymers via direct arylation and the Buchwald-Hartwig aryl amination reactions under aerobic conditions. Refluxing the reaction solvent and using XPhos Pd G2 as a precatalyst proved to be a tolerant polymerization protocol for direct arylation polycondensation, which eliminates the need for an inert gas atmosphere and can successfully proceed using commercially available, reagent-grade N,N-dimethylformamide (DMF) as the solvent. This strategy was also successfully applied to the Buchwald-Hartwig aryl amination polycondensation in toluene, which provided poly(triarylamine)s in air. Image 1 • The facile polycondensation via direct arylation in DMF under aerobic conditions has been demonstrated. • The protocol should provide an easy access to conjugated polymers without inert gas protection. • The facile protocol was also available for the Buchwald-Hartwig aryl amination polycondensation. [ABSTRACT FROM AUTHOR]

• Three steps to the synthesis of 2-methoxyestradiol with 63.3% overall yield. • The key step was the palladium-catalyzed direct C(sp2)-H methoxylation of 2-aryloxypyridines. • A new method to cleavage the pyridine-directing group, which is highly suitable for the substrates that bearing hydroxy. An efficient and concise synthesis of 2-methoxyestradiol (4) from 17β-estradiol (1) has been achieved in three synthetic steps with a 63.3% overall yield. The key step was the palladium-catalyzed direct C(sp2)-H methoxylation of 2-aryloxypyridines. Using 2-pyridyloxyl as the directing group, Pd(OAc) 2 as the catalyst, PhI(OAc) 2 as the oxidant and methanol as both the methoxylation reagent and solvent, the methoxy group could be handily installed at the 2-position of 3-(2-pyridoxy) estradiol (2). Subsequently, the pyridyl group could be easily removed by nucleophilic substitution with a methoxy anion after being oxidized to a pyridyl N -oxide by m -chloroperoxybenzoic acid, delivering the target product 2-methoxyestradiol (4) in quantitative yield. In contrast, when the pyridyl directing group was removed by the TfOMe-NaOMe/MeOH system as reported in the literature, TfOMe inevitably methylated the 17-OH of 2-methoxy-3-(2-pyridoxy) estradiol (3). In effect, we have fortuitously found a new method to cleave the pyridyl directing group, which is highly suitable for substrates bearing hydroxy groups. [ABSTRACT FROM AUTHOR]

• Palladium(II)-Pivaloyl thiourea complexes successfully synthesized and characterized. • The Pd(II) complexes gave significant results in the Sonogashira catalytic activity. • MC3 with no substitution exhibit the best catalyst as it gave a high conversion rate. We report herein the synthesis of Pd(II) complexes featuring pivaloylthiourea derivatives to investigate their catalytic behaviour in Sonogashira cross-coupling reactions as the homogenous catalyst. The SN 2 reactions have resulted in pivaloyl thiourea derivatives ligands with general formula (CH 3) 3 C(O)NHC(S)NHR introducing different substituent groups of NO 2 (L1), OCH 3 (L2), and H (L3) prior to form complexation with Pd(II) (MC1 , MC2 , and MC3 respectively). All synthesised compounds were characterised via typical selected spectroscopic and analytical methods. Hence, catalytic screening activity revealed that Pd(II)-pivaloyl thiourea catalysed, featuring MC3, is the best catalyst as it gave a high conversion rate up to 99%. [ABSTRACT FROM AUTHOR]

The Hirao reaction involving the phosphinoylation or phosphonation of aryl halides by >P(O)H reagents is a P–C bond forming transformation belonging to the recently very hot topic of cross-couplings. The Pd- or Ni-catalyzed variations take place via the usual cycle including oxidative addition, ligand exchange, and reductive elimination. However, according to the literature, the nature of the transition metal catalysts is not unambiguous. In this feature article, the catalysts described for the Pd(OAc)2-promoted cases are summarized, and it is concluded that the "(HOY2P)2Pd(0)" species (Y = aryl, alkoxy) is the real catalyst. In our model, the excess of the >P(O)H reagent served as the P-ligand. During the less studied Ni(II)-catalyzed instances the "(HOY2P)(−OY2P)Ni(II)Cl−" form was found to enter the catalytic cycle. The newest conclusions involving the exact structure of the catalysts, and the mechanism for their formation explored by us were supported by our earlier experimental data and theoretical calculations. [ABSTRACT FROM AUTHOR]

• Anti-inflammatory activities of benzo[ c ]phenanthridines were explored. • These compounds were obtained via a new and multi-step sequence. • Constructing isocoumarin ring and intramolecular arene-allyl cyclization were key steps. • Compound 7a was identified as first benzo[ c ]phenanthridine based PDE4 inhibitor. • 7a showed selectivity, microsomal stability, inhibition of TNF-α and no major toxicities in vitro. In spite of their various pharmacological properties the anti-inflammatory potential of benzo[ c ]phenanthridines remained underexplored. Thus, for the first time PDE4 inhibitory potential of 11,12-dihydro benzo[ c ]phenanthridine/benzo[ c ]phenanthridine was assessed in vitro. Elegant synthesis of these compounds was performed via a multi-step sequence consisting of a Pd-catalyzed unusual construction of 4-allyl isocoumarin ring and FeCl 3 -mediated intramolecular regio- as well as site-selective arene-allyl cyclization as key steps. The overall strategy involved Sonogashira coupling followed by isocoumarin and isoquinolone synthesis, then chlorination and subsequent cyclization to afford a range of 11,12-dihydro derivatives. One of these dihydro compounds was converted to the corresponding benzo[ c ]phenanthridine that showed concentration dependent inhibition of PDE4B affording an initial hit molecule. The SAR study suggested that 11,12-dihydro analogs were less potent than the compound having unsaturation at the same part of the ring. [ABSTRACT FROM AUTHOR]

Background: The Hirao reaction discovered ca. 35 years ago is an important P-C coupling protocol between dialkyl phosphites and aryl halides in the presence of Pd(PPh3)4 as the catalyst and a base to provide aryl phosphonates. Then, the reaction was extended to other Preagents, such as secondary phosphine oxides and H-phosphinates and to other aryl and hetaryl derivatives to afford also phosphinic esters and tertiary phosphine oxides. Instead of the Pd(PPh3)4 catalyst, Pd(OAc)2 and Ni-salts were also applied as catalyst precursors together with a number of mono- and bidentate P-ligands., Objective: In our review, we undertook to summarize the target reaction with a special stress on the developments attained in the last 6 years, hence this paper is an update of our earlier reviews in a similar topic., Conclusions: "Greener" syntheses aimed at utilizing phase transfer catalytic and microwave-assisted approaches, even under "P-ligand-free. or even solvent-free conditions are the up-to date versions of the classical Hirao reaction. The mechanism of the reaction is also in the focus these days., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)