28099-28-7

A series of novel three-armed star-shaped liquid crystals based on 1,3,5-trihydroxybenzene as a core and ω-[4-(p-alkoxybenzoloxy) phenoxycarbonyl]valeric acid as mesogenic arms were synthesized. Their chemical structures were confirmed by FTIR and 1

A new bio-inspired approach is reported for amide and peptide synthesis using α-amino esters that possess a potential activating group (PAG) at the ester residue. To activate the ester functionality under mild metal-free conditions, we exploited the facile dearomatization of phenols with hypervalent iodine(iii) reagents. Using a pyridine-hydrogen fluoride complex, highly reactive acyl fluoride intermediates can be successfully generated, thereby allowing for the smooth formation of sterically hindered amides and peptides from bulky amines and α-amino esters, respectively.

Herein, we report an unprecedented Cross Redox Coupling (CRC) reaction catalyzed by Cu(OAc)2·H2O. As a proof-of-concept, direct coupling of aromatic aldehydes (or alcohols) and p-benzoquinone led to an ester in the presence of the Cu(II)-TBHP combination. During the coupling process, the C-H bond of the aldehydes was converted directly to a C-O bond. Mechanistically, we propose that the reaction proceeded via a radical pathway. In addition, atom and electron economies were well-conserved during this CRC reaction.

Three star-shaped compounds (SSCs, c1-c3), are synthesized by using melitose as the chiral core and monacid (b1, b2 and b3) as side arms, respectively. The side arms (b1, b2 and b3), in which terminal chains are different, are introduced into the hydroxyl groups of melitose by esterification, respectively. The chemical structures of c1-c3 are confirmed by FT-IR and 1H NMR. The roles played by the chiral core and the side arms in the mesomorphic properties of the SSCs are studied. b1 is not a liquid crystal (LC), while b2 and b3 are nematic LCs. c1 is not a LC, while c2 and c3 are star-shaped LCs (SSLCs) and exhibit fingerprint texture of chiral nematic. c1, c2 and c3 are all levo-SSCs, which are different from their parent cores. The absolute value of their specific rotation increases with the increase of the terminal chain length of the side arms. The melting temperature of SSCs decreases with the increase of the terminal chain length of the side arms. For c2-c3, their mesomorphic region increases with the increase of the terminal chain length of the side arms. The results suggest that the LC properties of the side arms play an important role in inducing LC properties of the SSCs and the chiral core induces the chiral nematic of SSLCs, which contain the nematic LCs as the side arms.

2,2′-Bipyridines are known to coordinate to a wide variety of metal centres. In this paper, liquid-crystalline two-chained (dicatenar), four-chained (tetracatenar) and six-chained (hexacatenar) bipyridines are synthesised and their mesomorphism is described. For the tetracatenar bipyridines, a full homologous series, from tetramethoxy to tetratetradecyloxy, was synthesised, and the phase diagram showed a classic progression from nematic and smectic C phases at short chain length, through a cubic phase to a columnar phase.

The two series I and II of 1,1'-disubstituted ferrocenes which differ by the direction of the ester function included the rigid organic part were synthesized and their liquid crystal properties examined.These latter were found to be strongly dependent on the orientation of the connecting ester group and on the alkyl chain.

Three ester-type low molecular-weight liquid crystals having vinyl groups were synthesized and subjected to hydrosilylation, i.e., the reaction with polysiloxanes carrying hydrosilyl groups using a platinum compound as a catalyst.The thermotropic nature of the resultant liquid crystalline polymers (LCPs) was characterized.The application of the electric field changed the optical transparency of the LCPs.The effects of the applied voltage, the sample thickness and the frequency were studied.The results were explained by the theory developed for low molecular-weight liquid crystals, but a few different behaviors were also recognized.The observed electro-optic effects strongly suggest that the LCPs are not suitable as materials for displays due to slower responses, which are inherent in polymeric liquids.