Selective and controllable amination and defluoroamidation of α-trifluoromethylstyrene.

We present a blueprint for the amination and defluoroamidation of α-trifluoromethylstyrene. This practical protocol presents a general method for the diversity-oriented synthesis of vicinal trifluoromethyl amines and gem-difluoro alkenes from α-trifluoromethylstyrene maintaining excellent chemoselectivity. The synthetic strategy features outstanding atom economy and wide functional group tolerance under mild reaction conditions.

Suzuki-Miyaura Type Regioselective C-H Arylation of Aromatic Aldehydes by a Transient Directing Strategy.

Herein, we disclose a common approach for palladium-catalyzed direct coupling of the ortho-C-H bond of aromatic aldehydes with various organoboronic reagents by a transient directing strategy. In contrast to widely used cross-coupling reactions of C-H bonds with aryl halides, which generally need silver salt as a halide removal reagent, the method which used BQ/TFA as weak oxidation system for the PdII/Pd0 redox cycle is cost-effective, ecofriendly, and more aligned with green catalysis. This broadly applicable method opens up a new and efficient Suzuki-Miyaura coupling route for the direct formation of carbon-carbon bonds by C-H bond activation.

Electrostatic interaction between sulfated polysaccharides and oligopeptides from viral envelope glycoproteins using surface plasmon resonance.

Biotinylated oligopeptides from the envelope glycoproteins of dengue fever virus, influenza A and B viruses, and human immunodeficiency virus (HIV) were synthesized and their interaction with curdlan and dextran sulfates was investigated using surface plasmon resonance to evaluate the antiviral mechanisms of sulfated polysaccharides. More than two clusters consisting of basic amino acids in the oligopeptides from dengue fever virus, strongly interacted with the sulfated polysaccharides elucidated by the association- and dissociation-rate constants. Interactions decreased with the decreasing molecular weights of the sulfated polysaccharides. Although oligopeptides from influenza A virus potently interacted with the sulfated polysaccharides, no interaction was detected on a B/Hong Kong virus oligopeptide bearing few basic amino acids. For the C terminus and V3 region short and long oligopeptides from HIV gp120, the interaction was enhanced by the number of clustered basic amino acids and was inhibited by acidic and bulky amino acids.

Copper-Catalyzed Transamidation of Unactivated Secondary Amides via C-H and C-N Bond Simultaneous Activations.

Here, we demonstrate that α-C-H and C-N bonds of unactivated secondary amides can be activated simultaneously by the copper catalyst to synthesize α-ketoamides or α-ketoesters in one step, which is a challenging and underdeveloped transformation. Using copper as a catalyst and air as an oxidant, the reaction is compatible with a broad range of acetoamides, amines, and alcohols. The preliminary mechanism studies and density functional theory calculation indicated that the reaction process may undergo first radical α-oxygenation and then transamidation with the help of the resonant six-membered N,O-chelation and molecular oxygen plays a role as an initiator to trigger the transamidation process. The combination of chelation assistance and dioxygen selective oxygenation strategy would substantially extend the modern mild synthetic amide cleavage toolbox, and we envision that this broadly applicable method will be of great interest in the biopharmaceutical industry, synthetic chemistry, and agrochemical industry.

Supported Palladium Nanoparticles Catalyzed Intermolecular Carbopalladation of Nitriles and Organoboron Compounds.

The first heterogeneous catalyzed example for the direct synthesis of aromatic ketones via intermolecular carbopalladation of aliphatic nitriles and organoboron compounds was developed. This mild method proceeds with a supported palladium nanoparticles catalyst that could be reused and recycled five times. The fresh and used catalysts were characterized by XPS and TEM. The XPS analysis indicated that Pd0 was the active species for the reaction. This methodology provides a mild and cost-effective strategy for the efficient synthesis of ketones.

Mesoporous Carbon-Supported Pd Nanoparticles in the Metallic State-Catalyzed Acylation of Amides with Aryl Esters via C-O Activation.

Carbon, an abundant, inexpensive, and nonmetallic material, is an inimitable support in heterogeneous catalysis, and variable carbonaceous materials have been utilized to support metal nanoparticle catalysts. We developed an efficient and stable heterogeneous catalyst with highly dispersed metallic palladium nanoparticles embedded in an ordered pore channel of mesoporous carbon and first applied the catalyst to construct imides from amides using aryl esters as an acylation reagent via C-O activation. The catalyst represents excellent catalytic performance and could be reused and recycled five times without any significant decrease in activity. The heterogeneous nature of metallic state palladium was proven to be the active center in the acylation reaction.

Regiodivergent CDC reactions of aromatic aldehydes with unactivated arenes controlled by transient directing strategy.

The regiodivergent catalytic dehydrogenative cross-coupling reactions at both sp2 and sp3 hybridized carbons of aromatic compounds are particularly challenging. Herein, we report the finding of transient directing group controlled regiodivergent C(sp3)-C(sp2) and C(sp2)-C(sp2) cross-coupling in the o-methyl benzaldehyde frameworks. Catalyzed by palladium, using K2S2O8 or [F+] reagents as by-standing oxidants and unactivated arenes as substrates/solvents, various benzyl benzaldehydes or phenyl benzaldehydes were prepared. A mechanism study indicated that the regiospecificity is dominated by the [5,6]-fused palladacycle or [6,5]-fused palladacycle intermediates, which are generated from Pd-chelation with specified transient directing groups and further C-H activations.

[3 + 2 + 1] Pyridine Skeleton Synthesis Using Acetonitrile as C4N1 Units and Solvent.

The first [3 + 2 + 1] methodology for pyridine skeleton synthesis via cascade carbopalladation/cyclization of acetonitrile, arylboronic acids, and aldehydes was developed. This reaction proceeds via six step tandem reaction sequences involving the carbopalladation reaction of acetonitrile, a nucleophilic addition, a condensation, an intramolecular Michael addition, cyclization, and aromatization. Delightfully, both palladium acetate and supported palladium nanoparticles catalyzed this reaction with similar catalytic performance. The characterization results of the fresh and used supported palladium nanoparticle catalysts indicated that the reaction might be performed via a Pd(0)/Pd(II) catalytic cycle that began with Pd(0). Furthermore, the products showed good fluorescence characteristics. The green homogeneous/heterogenous catalytic methodologies pave a new way for constructing the pyridine skeleton.

A dual role for acetohydrazide in Pd-catalyzed controlled C(sp3)-H acetoxylation of aldehydes.

The palladium catalyzed aldehyde directed acetoxylation of C(sp3)-H bonds was realized by a transient directing group approach for the first time. Crucial to the successful outcome of this reaction is the dual role of acetohydrazide as a directing group for the catalytic C(sp3)-H activation process and as a protecting group for the CHO functional group. The applicable methodology exhibits good functional group tolerance and occurs readily under mild conditions.

Heterogeneous Suzuki-Miyaura coupling of heteroaryl ester via chemoselective C(acyl)-O bond activation.

A site-selective supported palladium nanoparticle catalyzed Suzuki-Miyaura cross-coupling reaction with heteroaryl esters and arylboronic acids as coupling partners was developed. This methodology provides a heterogeneous catalytic route for aryl ketone formation via C(acyl)-O bond activation of esters by successful suppression of the undesired decarbonylation phenomenon. The catalyst can be reused and shows high activity after eight cycles. The XPS analysis of the catalyst before and after the reaction suggested that the reaction might be performed via a Pd0/PdII catalytic cycle that began with Pd0.

Transesterification of (hetero)aryl esters with phenols by an Earth-abundant metal catalyst.

Readily available and inexpensive Earth-abundant alkali metal species are used as efficient catalysts for the transesterification of aryl or heteroaryl esters with phenols which is a challenging and underdeveloped transformation. The simple conditions and the use of heterogeneous alkali metal catalyst make this protocol very environmentally friendly and practical. This reaction fills in the missing part in transesterification reaction of phenols and provides an efficient approach to aryl esters, which are widely used in the synthetic and pharmaceutical industry.

Ring-opening polymerization of new 3-O-branched 1, 6-anhydro glucopyranose di- and trisaccharide monomers.

New 3-O-branched 1, 6-anhydro glucopyranose disaccharide monomers, 1, 6-anhydro-2, 4-di-O- benzyl-3-O-(2', 3', 4', 6'-tetra-O-benzyl-α-D-mannopyranosyl)- (LGM 6) and -glucopyranosyl)-ß-D- glucopyranose (LGG 7), and a trisaccharide monomer, 1, 6-anhydro-2, 4-di-O-benzyl-3-O-α-(2', 3', 6', 2″, 3″, 4″, 6″-hepta-O-benzyl- α-D-maltopyranosyl)-ß-D-glucopyranose (LGMAL 8), were synthesized and polymerized. It was found that the 3-O-branched1, 6-anhydro disaccharide monomers were polymerized. However, the polymerizability was lower than that of the 4-O-branched disaccharide monomers reported previously, and the trisaccharide monomer was not polymerizable, probably due to the steric hindrance of the branched bulky mono and disaccharide units at the 3-O position in 1, 6-anhydro glucopyranose. Debenzylation of the resulting polymers gave 3-O-gluco- and mannopyranosidic (1 â†’ 6)-α-D-glucopyranans in moderate yields. These results are the first reports of the polymerization of 3-O-branched 1, 6-anhydro glucopyranose disaccharide monomers to give 3-O-branched polysaccharides.