Shi-Kai Xiang

Synthesis of naphthalene derivatives through inexpensive BF 3 ·Et 2 O-catalyzed annulation reaction of arylacetaldehydes with arylalkynes

An inexpensive BF3·Et2O-catalyzed annulation reaction of arylacetaldehydes with arylalkynes has been developed. Various substituted phenylacetaldehydes and phenylacetylenes can undergo this reaction, producing corresponding α-aryl substituted naphthalene derivatives. Use of inexpensive and readily available BF3·Et2O catalyst constitutes the most attractive advantage of this transformation.

Influence of peripheral alkyl chain length on the mesomorphic behaviours of hexasubstituted triphenylene 2,3-dicarboxylic esters

ABSTRACT A comparative study of our established synthetic approaches to hexasubsituted triphenylenes 2,3-dicarboxylic esters containing four identical β-alkoxy and two adjacent β-alkoxycarbonyl side chains shows that the phase behaviours of small-sized discotic liquid crystals can be tailored over a wide range by simply varying the length of the peripheral alkyl chains. All the prepared esters in two series were observed to form a single hexagonal columnar phase, except for Tp4-1 having four β-butyloxy and two adjacent β-methoxycarbonyl chains which displays two columnar mesophase behaviours with a transition from the columnar plastic phase to hexagonal columnar phase. A significant difference between the two mesophase was observed in the variable temperature X-ray diffraction studies, and the mesophase assignment was also confirmed by polarising optical microscopy and differential scanning calorimetry. Moreover, the prepared esters in each series display the general trend of decreasing clearing temperature upon increasing alkoxy or alkoxycarbonyl chains length. The intermediate triphenylene 2,3-dicarboxylic acids were also found not only to exhibit columnar hexagonal mesophase over a narrower temperature range by maintaining high melting and clearing points but also to form organogel on mixing with toluene or dichloromethane with the assistance of hydrogen bonding. GRAPHICAL ABSTRACT

Heptasubstituted triphenylene 2,3-dicarboxylic esters discotic liquid crystals with three different types of peripheral substitution

ABSTRACT Hexasubstituted triphenylene (1a) containing four alkoxy and two adjacent methoxycarbonyl tails can be smoothly brominated or nitrated at its α-position(s) of two electron-rich rings to give a series of bromides and nitro compounds through electrophilic aromatic substitutions. Positions of bromo or nitro groups in target compounds were unambiguously established by combined analysis of 2D nuclear magnetic resonance experiments including nuclear Overhauser effect and heteronuclear multiple-bond correlation which indicated that monobromination or mononitration occurred preferentially at position 8 or 5 of 1a, respectively. Calculations of molecular geometry on 2a–e reveal that the α-Br or α-NO2 group(s) would induce different degrees of helical deformation in the triphenylene core and the degree of non-planarity decrease in the following order: 2c > 2b > 2e > 2a > 2d. In contrast to highly twisted 2b–c and 2e, which did not form a mesophase, the formation of a hexagonal columnar phase at room temperature even down to −50°C was observed and confirmed by polarising optical microscopy and X-ray diffraction for sterically less hindered, monosubstituted 2a and 2d. Graphical Abstract

Copper-Catalyzed Regioselective C-H Sulfonyloxylation of Electron-Rich Arenes with p-Toluenesulfonic Acid and Sulfonyloxylation of Aryl(mesityl)iodonium Sulfonates

Copper-catalyzed regioselective C-H sulfonyloxylation of electron-rich arenes with p-toluenesulfonic acid has been developed. Electron-rich benzene derivatives and heteroarenes can undergo this C-H sulfonyloxylation reaction to generate aryl tosylates. Furthermore, sulfonyloxylation of aryl(mesityl)iodonium sulfonates has also been investigated. Both aryl(mesityl)iodonium tosylates and triflates can react smoothly to get aryl sulfonates. The formed aryl sulfonates can be converted to phenols, as well as used as good partners of cross-coupling reactions.

Construction of Unsymmetrical Triphenylenes from Electron-Rich Biphenyls and Diaryliodonium Salts via Copper-Catalyzed Multiple C–H Arylation

An efficient protocol to synthesize unsymmetrical triphenylenes from electron-rich biphenyls and diaryliodonium salts via Cu catalysis was developed. A variety of unsymmetrical triphenylenes with diversified functional groups were synthesized according to this method. This transformation went through multiple direct C-H arylations from easily produced starting materials with high step-economy. The gram-scale synthesis of triphenylenes and their facile transformation into diverse functional organic molecules were illustrated.

Synthesis, structure and properties of polysubstituted benzo[g]chrysene by FeCl3-promoted from diphenylacetypene and phenylacetaldehyde derivatives

A new and straightforward method has been developed to synthesize polysubstituted benzo[g]chrysene (BgCh) according to controlling the exact stoichiometry of FeCl3 from diphenylacetypene and phenylacetaldehyde derivatives under mild conditions. The BgCh derivatives can also be functionalized by halogenation with Cl, Br and I on the newly built aromatic ring. All the compounds have been fully characterized as well as their photophysical properties, and some of them demonstrated extraordinary liquid crystallinity. The compounds 4e, 4h, 5e and 5h exhibited hexagonal columnar mesophases (Colh). In particular, 5h showed a rectangular columnar plastic phase (Colrp) under 35 °C on cooling. The fluorescence spectra of BgCh revealed a strong emission peak at 405 nm and a shoulder peak near 424 nm in DCM in the range of blue light.