Advances in liquid crystalline conjugated polymers

We review advances in liquid crystalline (LC) conjugated polymers by focusing on (i) ferroelectric and (ii) photoresponsive LC conjugated polymers. In Part 1, LC polyphenylene derivatives were synthesized through substitution of fluorine‐containing chiral LC groups into side chains. Poly(para‐phenylene) [ P1 ] and poly(meta‐phenylene) [ P2 ] derivatives showed chiral smectic C phases responsible for ferroelectricity. They exhibited quick response to electric field, giving switching times of <1 s between two bistable states. The spontaneous polarization (P_S) of P2 remained unchanged even after the electric field became zero, affording the residual polarization (P_R) whose value was the same as that of P_S. This indicates that P2 has a potential memory function based on FLC nature. In Part 2, poly(para‐phenylenevinylene) [ P5 ] and poly(bithienylene‐phenylene) [ P6 ] derivatives were synthesized by introducing dithienylethene moieties into side chains. Drastic quenching of fluorescence occurred when the photoresponsive moiety changed from an open form to a closed one upon an irradiation of ultraviolet light. The quenched fluorescence was recovered through a photoisomerization from the closed form to the open one. Macroscopically aligned P6 film exhibited a linearly polarized fluorescence with significant anisotropy. Reversible quenching and emitting behavior in anisotropic fluorescence was controlled by the photochemical switching. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2463–2485, 2009     

Highly Efficient Asymmetric Synthesis of Vinylic Amino Alcohols by Zn‐Promoted Benzoyloxyallylation of Chiral N‐tert‐Butanesulfinyl Imines: Facile and Rapid Access to (−)‐Cytoxazone

An efficient and convenient α‐hydroxyallylation approach for the asymmetric synthesis of a variety of β‐amino‐α‐vinyl alcohols has been successfully developed. A wide range of vinylic amino alcohol derivatives could be obtained in very good yields and with excellent diastereomeric ratios of up to 99:1 in favor of anti isomers by highly diastereoselective Zn‐promoted benzoyloxyallylation of chiral N‐tert‐butanesulfinyl imines with 3‐bromopropenyl benzoate at room temperature. In particular, excellent enantioinduction of the two new stereogenic centers was observed, with up to 98 % ee. The method provides a new route for the direct α‐hydroxyallylation of imines in a highly stereoselective manner. Moreover, the synthetic value of the method has also been demonstrated by the most concise and straightforward synthesis of (?)‐cytoxazone yet reported.     

Enantioselective Total Synthesis of Brevetoxin A: Unified Strategy for the B,E, G,and J Subunits

Brevetoxin A is a decacyclic ladder toxin that possesses 5‐, 6‐, 7‐, 8‐, and 9‐membered oxacycles, as well as 22 tetrahedral stereocenters. Herein, we describe a unified approach to the B, E, G, and J rings based upon a ring‐closing metathesis strategy from the corresponding dienes. The enolate technologies developed in our laboratory allowed access to the precursor acyclic dienes for the B, E, and G medium‐ring ethers. The strategies developed for the syntheses of these four monocycles ultimately provided multigram quantities of each of the rings, supporting our efforts toward the completion of a convergent synthesis of brevetoxin A.     

First Example of Highly Stereoselective Synthesis of 1,2,3‐Trisubstituted Cyclopropanes via Chiral Selenonium Ylides

A new strategy for the highly stereoselective synthesis of three stereoisomers of chiral 1,2,3‐trisubstituted cyclopropanes in good yields with excellent diastereoselectivities and very high enantioselectivities (up to >99 % ee) was developed via selenonium ylides (see scheme). Possible pathways for the asymmetric cyclopropanations were also proposed.

     

手性salen Mn(Ⅲ)的制备及其对α-甲基苯乙烯不对称环氧化反应的催化

本文以聚（苯乙烯-异丙烯膦酸）-磷酸氢锆（ZPS-IPPA）为载体,对该载体进行氯甲基化、胺化修饰后与手性Salen Mn(Ⅲ)轴向配位,合成了一种新的固载型手性Salen Mn(Ⅲ)催化剂,采用FTIR,DR UV-Vis,XPS,SEM,TEM,TG等手段对催化剂进行表征．以次氯酸钠和间氯过氧苯甲酸为氧化剂,考察了固载催化剂对ａ-甲基苯乙烯不对称环氧化反应的催化性能,结果表明,固载型催化剂的催化活性比相应均相催化剂略低,但对映体选择性明显提高．在NaClO/PPNO氧化剂体系中0 ℃反应24h,ａ-甲基苯乙烯环氧化物的转化率达68%,e.e.值达99%．循环使用8次后催化效果无明显降低．     

毛细管电泳氨类手性药物对映体拆分机理研究

手性药物及其对映体在药理上可表现出较大的差异,对它们进行研究将具有重要的理论意义和实用价值[1,2].毛细管区带电泳因其分离效率高、药品和试剂用量少、方法简单而成为目前手性拆分鉴定的重要方法之一[3].     

L-色氨酸甲酯氢溴酸盐与醛的高立体选择性Pictet-Spengler反应合成手性1,3-二取代-1,2,3,4-四氢-β-咔啉

研究了L-色氨酸甲酯氢溴酸盐与醛的Pictet-Spengler反应,该反应经过一个晶体诱导过程,高立体选择性地合成了一系列1,3-二取代-1,2,3,4-四氢-β-咔啉化合物,其结构经~1H NMR,IR,MS和元素分析表征.     

High-performance liquid chromatographic enantioseparation of methanobenzazocines

Chiral recognition and resolution of methanobenzazocines was investigated by HPLC using polysaccharide, Pirkle-type, native and derivatized β-cyclodextrin chiral stationary phases. Enantioseparation of phenyl substituted 2,6-methanobenzazocines was achieved with multiple chiral stationary phases throughout the classes described. Chiral resolution of the enantiomers of 1,5-methano-3-methyl-6-oxo-1,2,3,4,5,6-hexahydro-3-benzazocine was produced on both polysaccharide and Pirkle-type phases. In the case of 1,5-methano-3-methyl-6-phenyl-1,2,3,4,5,6-hexahydro-3-benzazocine only a dinitrophenyl substituted β-cyclodextrin produced a separation of enantiomers.     

Preparation of ferrocenyl imidazolines using bis(triphenyl)oxodiphosphonium trifluoromethanesulfonate

An efficient synthesis of ferrocenyl imidazolines starting from ferrocenyl carboxylic acids has been developed. Bis(triphenyl)oxodiphosphonium trifluoromethanesulfonate was used to convert smoothly ferrocenyl carboxylic amides bearing an amine side chain, derived from ferrocenyl carboxylic acids and 1,2-diamines, to their corresponding ferrocenyl imidazolines.     

The role of central ion in chiral recognition by taking phenylalanine as an example

Chiral recognition of phenylalanine (Phe) was achieved in the gas phase by electrospray ionization Q-TOF tandem mass spectrometry. In this method, two central ions, i.e. proton and divalent copper, were used and chiral crown ether, (+)-2,3,11,12-tetracarboxylic acid-18-crown-6 (18-C-6-TCA), was used as a chiral host. Dimeric complexes were readily formed by electrospray ionization of a methanol/water (50/50, V/V) solution containing central ions, Phe and 18-C-6-TCA. The dimeric complex included proton-bound (18-C-6-TCA)(Phe)H+ and copper-bound deprotonated [Cu²⁺(18-C-6-TCA)(Phe)-H]⁺ ions were mass selected and then collided with Ar in the CID experiments. The chiral recognition capability of these complexes was evaluated using the relative abundance of daughter ion to parent ion. A higher degree of chiral recognition ability was observed with Cu²⁺ compared to that of H⁺. Different central ions exhibited distinctive dissociation pathways and unique chiral recognition characteristics. The chiral recognition mechanism was also discussed in detail with the help of the structure of copper-bound complex predicted by theoretical calculation.