Indium-mediated regio- and diastereoselective reduction of norbornyl alpha-diketones

A novel, efficient, and regio- as well as diastereoselective conversion of non-enolizable bicyclic alpha-diketones into synthetically useful acyloins mediated by indium metal is described. The reduction is highly diastereoselective, leading exclusively to endo-acyloins (endo-hydroxyl groups) in excellent yields, and tolerates a variety of sensitive substituents, such as acetate, ester, and bridgehead halogens. The regioselectivity in the reductions of monosubstituted alpha-diketones varied from 70:30 to 100:0 for the two possible isomeric alcohols. The methodology is extended to the synthesis of highly functionalized cyclopentane carboxaldehydes, potential building blocks in organic syntheses, by cleavage of the acyloins by treating them with Pb(OAc)4 in MeOH/PhH. Allylindium additions to carboxaldehydes 22 have been found to be highly diastereoselective.     

Microwave synthesis of nanoporous materials.

Studies in the last decade suggest that microwave energy may have a unique ability to influence chemical processes. These include chemical and materials syntheses as well as separations. Specifically, recent studies have documented a significantly reduced time for fabricating zeolites, mixed oxide and mesoporous molecular sieves by employing microwave energy. In many cases, microwave syntheses have proven to synthesize new nanoporous structures. By reducing the times by over an order of magnitude, continuous production would be possible to replace batch synthesis. This lowering of the cost would make more nanoporous materials readily available for many chemical, environmental, and biological applications. Further, microwave syntheses have often proven to create more uniform (defect-free) products than from conventional hydrothermal synthesis. However, the mechanism and engineering for the enhanced rates of syntheses are unknown. We review the many studies that have demonstrated the enhanced syntheses of nanoporous oxides and analyze the proposals to explain differences in microwave reactions. Finally, the microwave reactor engineering is discussed, as it explains the discrepancies between many microwave studies.     

Spatial Arrangement and Preparative Organic Synthesis

This review deals with the stereoselective formation of organic compounds. A number of examples of such syntheses, especially those of alkaloids and steroids, are described. An asymmetric synthesis, which avoids the intricacies and wastefulness of optical resolution, has been successful in a few cases only. The procedures of configurational change and of optical resolution, as well as the planning of multi-step stereoselective syntheses, are discussed.     

Thiolation of symmetrical and unsymmetrical diketopiperazines

The introduction of sulfur units into a variety of symmetrical and unsymmetrical diketopiperazines (DKPs) is described. We investigated different thiolation methods utilizing several bases and electrophilic sulfur reagents, leading to monomethylthio-, bis(methylthio)-, and epithio-DKPs. Their formation proceeded diastereoselectively, facilitating the application in total syntheses of many thiodiketopiperazine (TDKP) natural products. Furthermore, possible side reactions as well as mechanistic studies and stereochemical structural assignments of the obtained products are given.     

Reactivity of 6-anisyl-5-cyano-4-oxo-2-thioxo-1,2,3,4-tetrahydro-pyrimidine to wards some electrophiles and nucleophiles

The title compound was subjected to react with some electrophiles and nucleophiles, such as alkyl halides, ethyl chloroacetate or amines, hydrazines etc. The resulting compounds were used in further syntheses for the purpose of obtaining some new types of heterocycles with possible biological and pharmaceutical activities.     

Synthesis of well‐defined functionalized polymers and star branched polymers by means of living anionic polymerization using specially designed 1,1‐diphenylethylene derivatives

This article covers precise syntheses of well‐defined chain‐end and in‐chain functionalized polymers, multi‐functionalized polymers with a definite number of functional groups, star‐branched and graft polymers by recently developed methodologies using specially designed 1,1‐diphenylethylene (DPE) derivatives. The DPE derivatives include various substituted DPE derivatives with functional groups and their derivatives, DPE‐functionalized DPE derivatives, and well‐defined DPE‐functionalized macromonomers. The synthetic utility and importance of these DPE derivatives are described via such polymer syntheses.     

Room-temperature biosynthesis of ferroelectric barium titanate nanoparticles

The syntheses of inorganic materials by biological systems is characterized by processes that occur close to ambient temperatures, pressures, and neutral pH, as is exemplified by biosilicification and biomineralization processes in nature. Conversely, laboratory-based syntheses of oxide materials often require extremes of temperature and pressure. We have shown here the extracellular, room-temperature biosynthesis of 4-5 nm ternary oxide nanoparticles such as barium titanate (BT) using a fungus-mediated approach. The tetragonality as well as a lowered Curie transition temperature in sub-10 nm particles was established, and the ferroelectricity in these particles was shown using Kelvin probe microscopy.     

Shaping Tetraazaparacyclophanes for Selective Solvent Vapour Detection: Structural Variations in Coating Design

Paracyclophanes serve well as receptor sites mimicking enzyme analogue recognition. Their application as coatings for themass-sensitive detection of toxic organic solvent vapours is demonstrated involving synthetic variation of the macrocycle in terms of cavity size, shape and stereoelectronics. In this way it is possible to tailor these hosts towards different analytes such as chloroform or toluene. The computational modelling of the inclusion allows the prediction of both the sensitivities and selectivities of promising coatings before doing time consuming syntheses. Force-field calculations show that the outstanding inclusion behaviour of a xylylene bridged tetraazaparacyclophane towards large aromatic and halogenated analyte molecules is due to the elongated cavity of the host. Temperature-dependent determination of the equilibrium constant K of the guest inclusion shows that calculated and measured interaction enthalpies do correlate satisfactorily.     

芳炔类共轭大环化合物

芳炔类大环化合物是最近10年来新兴的一种富碳共轭大环状分子，迅速发展到 近100种，可在光、电、磁、纳米等功能材料中得到广泛应用，引起了人们极大的 兴趣，对芳炔类大环化合物的研究，特别是合成方法和性质进行了综述，并提出了 这一领域的发展方向和需要解决的重点课题。     

Synthesis and characterization of some heterocyclic derivatives by cyclization of carbohydrate thiosemicarbazone — part II

The syntheses of 2,3‐dihydro‐1,3,4‐thiadiazoles and 1,3,4‐thiadiazoles from 1,2‐O‐isopropylidene‐α‐D‐xylo‐1,5‐pentadialdo‐1,4‐furanose thiosemicarbazone are described. The new compounds as well as the intermediate products are physically and spectroscopically characterized. We discuss a possible mechanistic pathway for heterocyclization in this particular substrate, using computational calculation.     

Asymmetric Total Syntheses,Stereostructures, and Cytotoxicities of Marine Bromotriterpenoids Aplysiol B (Laurenmariannol) and Saiyacenol A

There are marine cytotoxic bromotriterpenoids, named the thyrsiferol family that are structurally characterized by some tetrahydropyran (THP) and tetrahydrofuran (THF) rings. The thyrsiferol family belongs to natural products that are often difficult to determine their stereostructures even by the current, highly advanced spectroscopic methods, especially in acyclic systems including stereogenic tetrasubstituted carbon centers. In such cases, it is effective to predict and synthesize the possible stereostructures. Herein, to elucidate ambiguous stereostructures and unassigned absolute configurations of aplysiol B, laurenmariannol, and saiyacenol A, members of the thyrsiferol family, we carried out their asymmetric chemical syntheses featuring 6-exo and 5-exo oxacyclizations of epoxy alcohol precursors and 6-endo bromoetherification of a bishomoallylic alcohol. In this paper, we report total assignments of their stereostructures through their asymmetric chemical syntheses and also their preliminary cytotoxic activities against some tumor cells. These results could not have been achieved without depending on asymmetric total synthesis.     

Study on Atom Economic Process of Diethyl Oxalate Synthesis by CO Coupling in Gaseous Phase

The gaseous phase syntheses of diethyl oxalate and oxalic acid from CO are an important project of chemical technology^[1]. Oxygencontent of CO is as high as 57%(wt) and its source is abundant. It is best of all economical and reasonable that oxy-compound is synthesized with carbon monoxide. In particular the reaction of CO coupling reaction can take place under moderate reaction conditions with low consumption of energy to produce oxalic acid and diethyl oxalate, which are feed stocks for ethylene glycol syntheses by the hydrogenation of oxalate, as well as for products such as pesticides, pharmaceuticals, foodstuffs, polymers, and fine chemicals.     

Isocyanides in the synthesis of nitrogen heterocycles

Isocyanides have long proved themselves to be irreplaceable building blocks in modern organic chemistry. The unique features of the isocyano group make isocyanides particularly useful for the synthesis of a number of important classes of nitrogen heterocycles, such as pyrroles, indoles, and quinolines. Several cocyclizations of isocyanides via zwitterions and radical intermediates as well as transition-metal-catalyzed syntheses of different types of heterocycles have recently been developed. Methods starting from isocyanides often have distinct advantages over alternative approaches to the same heterocycles because of their enhanced convergence, the great simplicity of most of the operations with them, and the great variety of isocyanides readily available for use. Isocyanides have also been used in some enantioselective syntheses of chiral heterocyclic compounds, including natural products as well as precursors thereof.     

Strategy for enantio- and diastereoselective syntheses of all possible stereoisomers of 1,3-polyol arrays based on a highly catalyst-controlled epoxidation of alpha,beta-unsaturated morpholinyl amides: application to natural product synthesis

We describe a new strategy for enantio- and diastereoselective syntheses of all possible stereoisomers of 1,3-polyol arrays. This strategy relies on a highly catalyst-controlled epoxidation of alpha,beta-unsaturated morpholinyl amides promoted by the Sm-BINOL-Ph(3)As[double bond]O (1:1:1) complex, followed by a conversion of morpholinyl amides into ketones and diastereoselective ketone reduction. Highly enantio- (up to >99 % ee) or diastereoselective (up to >99.5:0.5) epoxidation was achieved using 5-10 mol % of the Sm complex to afford synthetically very useful, nearly optically pure alpha,beta-epoxy morpholinyl amides. Stereoselectivity of the epoxidation was controlled by the chirality of BINOL with overwhelming inherent diastereofacial preference for the substrate. Combination with the syn- and anti-selective ketone reduction with the highly catalyst-controlled epoxidation allowed for an iterative strategy for the syntheses of all possible stereoisomers of 1,3-polyol arrays. Eight possible stereoisomers of 1,3,5,7-tetraol arrays were synthesized with high to excellent stereoselectivity. Moreover, the efficiency of the present strategy was successfully demonstrated by enantioselective syntheses of several 1,3-polyol/alpha-pyrone natural products, for example, cryptocaryolone diacetate.     

Synthesis of Thiazole and Fused Thiazolo Derivatives

The syntheses of thiazole and fused thiazolo derivatives 2 – 4 , 6 – 8 , 10a – 11b , 13 – 16 from heterocylic isothiocyanates 1 , 5 , 9 , and 12 bearing an ortho ester group and bifunctional reagents, such as substituted propargylamines, is described. Different regioselectivity of intramolecular nucleophilic attack of the thiourea S-atom on the C ? C bond, resulting in the formation of both thiazolo and thiazino derivatives, as well as NMR structure elucidation are discussed.     

苯乙烯和丙烯酸系改性醇酸树脂涂料

综述了苯乙烯和丙烯酸系改性醇酸树脂的研究进展,介绍了该类树脂的合成、性能及应用,讨论了该类树脂的优缺点,预测了苯乙烯和丙烯酸系改性醇酸树脂涂料的发展趋势。     

Hydroxyl-directed cyclizations of 1,6-enynes

The palladium-catalyzed, hydroxyl-directed cyclization reactions of 1,6-enynes provide a highly diastereoselective process for the syntheses of stereochemically defined cyclopentanes. Consistently high levels of cis-selectivity are possible using homopropargyl alcohols in contrast to the corresponding propargyl alcohols. Hydroborylative enyne cyclizations coupled with this directing group effect provide a useful method for the syntheses of multifaceted compounds bearing all carbon quaternary centers.     

Concise syntheses of (±)-dichroanone, (±)-dichroanal B, (±)-taiwaniaquinol B, and (±)-taiwaniaquinone D

The total syntheses of dichroanone and dichroanal B, as well as the formal syntheses of taiwaniaquinol B and taiwaniaquinone D, are reported.     

Chemistry of the phenoxathiins IV. Synthesis of 9-substituted 1 -azaphenoxathiins

In an extension of recently reported syntheses of the I-azaphenoxathiin nucleus as well as several 7-substituted analogs, the synthesis of several 9-substituted members of this series is now reported. In addition, the first ¹³C-nmr spectral evidence of an interaction between a sulfur atom and the oxygen of an ortho-nilro group which has been previously observed only in X-ray erystallographic studies is also described. The possible consequences of this interaction on the reaction pathway leading to the cyclization of the 9-substituted J-azaphenoxathiin nucleus is also presented.     

Synthesis of Amaryllidaceae Constituents and Unnatural Derivatives

This update covers the syntheses of Amaryllidaceae alkaloids since the publication of the last major review in 2008. A short summary of past syntheses and their step count is provided for the major constituents; pancratistatin, 7‐deoxypancratistatin, narciclasine, lycoricidine, lycorine, and for other natural constituents, as well as for unnatural derivatives. Discussion of biological activities is provided for unnatural derivatives. Future prospects and further developments in this area are covered at the end of the review. The literature is covered to the end of August 2015.