Charge Separation in Excited States of Decoupled Systems—TICT Compounds and Implications Regarding the Development of New Laser Dyes and the Primary Process of Vision and Photosynthesis

The understanding of the dual fluorescence of certain aromatic systems has greatly advanced in recent years. The accompanying large charge separation has been shown to be linked to a twisted (or small overlap) arrangement of the chromophores. Recent theoretical models are able to describe the excited-state twisting of both single bonds (TICT compounds) and double bonds (olefins) in a unified picture. These models can help to elucidate the photophysical behavior of many organic, inorganic, and biologically relevant compounds, and their application to laser dyes and fluorescent probes provides a route to new “tailor-made” fluorescent materials. Applied to the primary processes of vision and photosynthesis, these models can lead to a deeper understanding of basic photobiological processes.     

Simultaneous Chain‐Growth and Step‐Growth Polymerization—A New Route to Cyclic Polymers

Reinvestigation of numerous ring‐opening polymerizations by means of MALDI‐TOF mass spectrometry has evidenced that cyclic polymers were formed as the only reaction products or, at least, in large fractions. This finding is ascribed to the intermediate formation of difunctional chains having active end groups that can react with each other. Due to the low concentration of these difunctional chains cyclization is favored over chain extension according to the Ruggli–Ziegler dilution principle. A polymerization mechanism which usually favors the formation of cyclic polymers is the zwitterionic polymerization, but an exception from this rule is known. The following classes of monomers were discussed: α‐amino acid, N‐carboxyanhydrides (oxazolidine‐2,5‐diones), dithiolane‐2,4‐diones, 5,5‐dimethyl‐1,3,2‐dioxathiolan‐4‐one‐2‐oxide, salicylic acid O‐carboxyanhydride, L ‐lactide and D ,L ‐lactide, hexamethyl cyclotrisiloxane, and macrocyclic dithiocarbamates.

     

A Nanojunction Polymer Photoelectrode for Efficient Charge Transport and Separation

A metal‐free photoanode nanojunction architecture, composed of B‐doped carbon nitride nanolayer and bulk carbon nitride, was fabricated by a one‐step approach. This type of nanojunction (s‐BCN) overcomes a few intrinsic drawbacks of carbon nitride film (severe bulk charge recombination and slow charge transfer). The top layer of the nanojunction has a depth of ca. 100 nm and the bottom layer is ca. 900 nm. The nanojunction photoanode results into a 10‐fold higher photocurrent than bulk graphitic carbon nitride (G‐CN) photoanode, with a record photocurrent density of 103.2 μA cm⁻² at 1.23 V vs. RHE under one sun irradiation and an extremely high incident photon‐to‐current efficiency (IPCE) of ca. 10 % at 400 nm. Electrochemical impedance spectroscopy, Mott–Schottky plots, and intensity‐modulated photocurrent spectroscopy show that such enhancement is mainly due to the mitigated deep trap states, a more than 10 times faster charge transfer rate and nearly three times higher conductivity due to the nanojunction architecture.     

邻芳基苯基膦酸酯的新合成路线

以磷酸苯酯为原料,经碱性重排、O-磺酰化和Suzuki偶联反应合成邻芳基苯基膦酸酯是一条方便合理的路线.     

A New Route for Synthesis of Entecavir

2-Amino-1,9-dihydro-9-[(1S,3R,4S)-4-hydroxy-3-(hydroxymethyl)-2-methylenecyclopen tyl]-6H-purin-6-one (entecavir, Scheme 1) is a novel carbocyclic 2-deoxyguanosine analog drug which has potent and selective anti hepatitis B virus (HBV) activity1-3. Entecavir is also effective against lamivudine-resistant YMDD mutants4. The US Food and Drug Administration (FDA) approved entecavir as a new preferred drug for the treatment of HBV after lamivudine in March, 2005. Scheme 1 The structure o…     

A New Route for the Synthesis of (±)-Seudenol

Seudenol (3-methyl-2-cyclohexen-1-ol) is an aggregation pheromone isolated from female hindguts of the Douglas fir beetle, ^{Dendroctonus pseudotsugae},by Vité^[l]. Sivlerstein reported that the natural seudenol is racemic^[2]. Racemic seudenols have been synthesized by various methods^[3-5], almost all of which have used 3-methyl-2-cyclohexen-1-one (4) as precursor or intermediate, followed by reduction. Among reduction of enone (4), most systems studied to date have focused on selective reduction of α, β-unsaturated ketone to the corrsponding allylic alcohol. But most of the reduction required special and expensive reagent^[3-5]. In this paper,a new convenient material route was reported to synthesize (±)-seudenol. The route is illustrated in the following scheme.     

A New Route for the Preparation of Brain‐Like Nanostructured Polyaniline

A novel approach has been explored to prepare brain‐like polyaniline (PANI) nanostructures with many convolutions (140–170 nm in average diameter) using aniline/citric acid (CA) salt as the template and chlorine gas as the oxidant by a gas/solid reaction for the first time. The method provided here differs significantly from the traditional one in which the polymerization of PANI is usually carried out in acidic solution.

     

奥利司他的合成新路线

利用Mukaiyama-aldol反应、Noyori还原反应、Frater-Seebach烷基化反应构建奥利司他分子的3个关键手性中心,实现了奥利司他的全合成.     

From an Insecticide to Plato's Universe—The Pagodane Route to Dodecahedranes: New Pathways and New Perspectives

The original concept for the synthesis of pentagonal dodecahedranes by the conversion of structurally similar, high-energy [1.1.1.1]pagodanes relied on catalytic dehydrocyclizations. As a consequence, preparative limitations were preprogrammed. With multiple functionalization of these pagodanes, alternative cyclization methods became viable. These efficient processes allowed access to a multitude of pentagonal and nonpentagonal, carba- and heterocyclic dodecahedral skeletons with widely variable substitution patterns. Such a roundabout route provided the (CH)₂₀ basic framework with high efficiency, and long-lacking thermochemical data could be ascertained calorimetrically. In spite of the unusually pronounced pyramidalization of their olefinic centers, singly and doubly unsaturated dodecahedranes with isolated C?C bonds proved to be kinetically quite stable, but underwent dimerization on thermal activation. Dodecahedranes with a higher degree of unsaturation (trienes–decaenes, C₂₀ fullerene?) have been found so far only in the gas phase. Higher fullerenes, including C₆₀, have been identified by mass spectrometry after exposure of halogenated dodecahedranes and pagodanes to a 248-nm excimer laser. Transannular electron delocalization has been verified for the “slender” pagodane/isopagodane and even for the “spherical” dodecahedrane cages.     

Lithiated Primary Amine—A New Material for Hydrogen Storage

A facile method for synthesizing crystalline lithiated amines by ball milling primary amines with LiH was developed. The lithiated amines exhibit an unprecedented endothermic dehydrogenation feature in the temperature range of 150–250 °C, which shows potential as a new type of hydrogen storage material. Structural analysis and mechanistic studies on lithiated ethylenediamine (Li₂EDA) indicates that Li may mediate the dehydrogenation through an α,β‐LiH elimination mechanism, creating a more energy favorable pathway for the selective H₂ release.     

A New Route to Monoalkylhydrazines

Electrophilic amination of primary amines with N-(dietho-xyphosphoroyl)-O-(p-nitrophenylsulfonyl)-hydroxylamine 1, followed by dephosphorylation of the phosphorohydrazidate 2 with p-toluenesulfonic acid monohydrate in ethanol, represents a novel approach to monoalkylhydrazines.