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Regioselective functionalization of arenes remains a challenging problem in organic synthesis. Steric interactions are often used to block sites adjacent to a given substituent, but they do not distinguish the remaining remote sites. We report a strategy based on remote steric control, whereby a roof-like ligand protects the distant para site in addition to the ortho sites, and thereby enables selective activation of meta carbon-hydrogen (C–H) bonds in the absence of ortho or para substituents. We demonstrate this concept for iridium-catalyzed meta -selective borylation of various monosubstituted arenes, including complex drug molecules. This strategy has the potential to expand the toolbox of C–H bond functionalization to previously nondifferentiable reaction sites.

Nano-sized energetic particle as fuel additives is of great significance for liquid hydrocarbon fuels that will exhibit high-density and high-calorific value in high-speed propulsion systems. An experimental investigation has been conducted to determine the propulsive and combustion behavior of hydrocarbon fuels containing boron nanoparticles. In this study, nano-sized boron particles with average diameter of 20 nm are added into the basic fuel JP-10 and quadricyclane, respectively. They are then referred as slurry fuels and burned in the rocket combustor using pure oxygen as the oxidizer. With a wide range of excess oxidizer coefficients, three parameters characterizing the propulsion performance are employed to evaluate the effect of boron nanoparticles on hydrocarbon fuels. It is found that the boron-based slurry fuel showed superior density specific impulse. It is increased by 1.18% and 1.44% when the addition of boron particles with 10% mass fraction are added into the basic fuel JP-10 and quadricyclane, respectively. Combustion depositions of the boron-based slurry fuel located at different positions are then collected for deep analysis by means of the energy dispersive spectrometer, X-ray diffractometer, and scanning electron microscope. Comprehensive microanalysis results demonstrate that boron particles first combine with the C-element in the hydrocarbon fuel to form the boron carbide with a reticular structure, and then the boron carbide oxidizes to form block-shaped boron oxide. However, the surface boron oxide hindered the further reaction of the internal boron carbide, which limits the energy release of the boron particles and ultimately leads to the unsatisfactory combustion efficiency of the slurry fuel.

A highly efficient carboxylation of benzyl alcohol derivatives with CO 2 using a palladium/iridium dual catalyst under visible-light irradiation was developed. A wide range of benzyl alcohol derivatives can be employed to provide benzylic carboxylic acids in moderate to high yields. Mechanistic studies indicated that the oxidative addition of benzyl alcohol derivatives was possibly the rate-determining-step. It was also found that a switchable site-selective carboxylation between benzylic C-O and aryl C-Cl moieties can be achieved simply by changing the palladium catalyst.

The ZNF280D is a member of the C2H2 zinc finger family, which plays important roles in cell and organismal growth, secretion, and other biological processes. This study aimed to identify the alternative splicing of pig ZNF280D, and to predict the structure and function of the encoded proteins, as well as to study the spatio-temporal expression patterns of each transcript. RNA-seq and qPCR technology were used to identify the transcripts of pig ZNF280D. We found two transcripts, ZNF280D1 and ZNF280D2 (GenBank accession number: MF279143). ZNF280D1 is the common transcript, whereas ZNF280D2 lacked a large region at exon 8. In addition, ZNF280D2 had an additional C2H2 zinc finger domain, changing the protein from a tC2H2 to a maC2H2 zinc finger protein. The expression of two transcripts in various tissues of pig was differ significant. ZNF280D2 is the main subtype. The expression of ZNF280D2 in pig muscle was found to increase gradually with age. The ZNF280D1 was first decreased and then increased slightly. We successfully identified two transcripts of pig ZNF280D, and we suggested important functions for ZNF280D in digestive absorption and growth as well as in the development of skeletal muscles, the specific mechanisms for which would require further study.

The Rh-catalyzed direct carboxylation of alkenyl C-H bonds was achieved by using pyrazole as a removable directing group. In the presence of 5 mol% RhCl3 ⋅ 3H2 O, 6 mol% P(Mes)3 , and 2 equiv. of AlMe2 (OMe), the alkenyl C-H bond of various alkenylpyrazoles was directly carboxylated in good yields under CO2 atmosphere. Furthermore, several useful transformations of the pyrazole moiety of the product were achieved to afford synthetically useful carboxylic acid derivatives in good yields.

A chemoselective hydrogenation of isoquinoline carbocycles was achieved by using the catalyst prepared from Ru(methallyl)2(cod) and trans-chelate chiral ligand PhTRAP. The unique chemoselectivity achieved in this hydrogenation could be ascribed to the trans-chelation of the chiral ligand. The procedure for preparing the catalyst strongly affects the reproducibility of the carbocycle hydrogenation. Various 5-, 6-, 7-, and 8-substituted isoquinolines were selectively hydrogenated at their carbocycles to afford 5,6,7,8-tetrahydroisoquinolines as major products in high yields with moderate or good enantioselectivities. Some mechanistic studies suggested that the stereogenic center was created during the initial addition of H2 to the aromatic ring in the hydrogenation of 5-substituted isoquinolines. In other words, the stereochemical control was accompanied by the dearomatization.

Transition-metal-catalyzed asymmetric α-arylation of carbonyl compounds is a widely studied method for C-C bond formation. Recently, the α-arylation of α-fluoro ketones has been reported, including enantioselective α-arylation of α-fluoro ketones. However, the asymmetric α-arylation of α-fluoro carbonyl compounds in the carboxylic acid oxidation state has not been reported. We report the enantioselective α-arylation of α-fluorooxindoles with aryl triflates. The reaction occurs in high yield and with high enantioselectivity when catalyzed by a Pd-Segphos complex. This general class of product serves as an enantioenriched, nonenolizable version of α-aryl oxindoles.

The transition-metal-catalyzed α-arylation of carbonyl compounds is a widely practiced method for C–C bond formation. Several enantioselective versions of this process have been reported, but intermolecular, enantioselective coupling reactions of aryl electrophiles with α-fluoro carbonyl compounds have yet to be disclosed. We report enantioselective coupling of aryl and heteroaryl bromides and triflates with α-fluoroindanones catalyzed by palladium complexes of a BINOL-derived monophosphine and Segphos, respectively. The enolates were generated directly from α-fluoroindanones in the presence of potassium phosphate base during the reactions. We also report that reactions of α-fluorotetralones occur in high yields and enantioselectivities when conducted with enolates generated by elimination of trifluoroacetate from trifluoromethyl β-diketone hydrates. These reactions were catalyzed by palladium complexes of the commercially available bisphosphine Difluorphos. Thus, the formation of enantioenriched α-aryl-α-fluoroketones can be readily achieved by C–C bond formation when the appropriate palladium catalyst and α-fluoro enolate precursor were used. MOE (Min. of Education, S’pore) Accepted version

The palladium complex, which is generated in situ from Pd(η 3-C3H5)Cp and tris(4-methoxy-3,5-dimethylphenyl)phosphine, catalyzed the [4+2] cycloaddition of o-(silylmethyl)benzyl carbonates with alkenes. The reaction of the benzyl esters with methyl crotonate gave methyl 3-methyltetralin-2-carboxylate in 84% yield with 2% catalyst loading.

Tris(4-methoxy-3,5-dimethylphenyl)phosphane is evaluated as the ligand in hitherto unsuccesful Pd-catalyzed transformations to substituted 1,2,3,4-tetrahydronaphthalenes.