Seven- and Eight-Membered Ring Conformations of Phosphorus Containing Heterocycles

Abstract

The conformational behaviour of seven- and eight-membered heterocycles based on their NMR spectrum and on a theoretical investigation is described. All possible basic conformations and their quantitative parameters have been considered. A molecular mechanics approach is applied to the calculation of the multidimensional maps of potential energy dependence on torsional angles.     

Orthobromodiphenylmethane Derivatives as Starting Materials for the Total Synthesis of Anthraquinones

In this communication we describe the synthesis of four simple anthraquinones by a five-step sequence, using easily available bromobenzaldehydes and phenyllithium derivatives as starting materials.     

Nucleophilic Substitution of 4H-Imidazolesby Thioles: New Starting Materials for Tetraazafulvalenes and Fused Heterocycles

 Different reactivities towards the 4H-imidazoles 1 depending on the nature of the sulfur containing nucleophile were observed. Whereas H₂S and aromatic thioles led to 4,5-diaminoimidazoles in the course of a reduction process, treatment with aliphatic mercaptanes resulted in a substitution-reduction-dimerization cascade which finally gave bis-imidazoles. Their oxidative modification in presence of m-chloroperbenzoic acid then allowed new 1,3,5,7-tetraazafulvalenes to be easily obtained. Treatment of the bis-imidazoles with acetylene dimethyldicarboxylate caused cleavage of the central bond, thus leading to the formation of derivatives which are of interest for the transformation into fused heterocycles such as imidazo[4,5-b]azepines.     

Nucleophilic Substitution of 4H-Imidazolesby Thioles: New Starting Materials for Tetraazafulvalenes and Fused Heterocycles

Summary.  Different reactivities towards the 4H-imidazoles 1 depending on the nature of the sulfur containing nucleophile were observed. Whereas H₂S and aromatic thioles led to 4,5-diaminoimidazoles in the course of a reduction process, treatment with aliphatic mercaptanes resulted in a substitution-reduction-dimerization cascade which finally gave bis-imidazoles. Their oxidative modification in presence of m-chloroperbenzoic acid then allowed new 1,3,5,7-tetraazafulvalenes to be easily obtained. Treatment of the bis-imidazoles with acetylene dimethyldicarboxylate caused cleavage of the central bond, thus leading to the formation of derivatives which are of interest for the transformation into fused heterocycles such as imidazo[4,5-b]azepines. Received May 22, 2000. Accepted June 19, 2000     

Bis(β-Difunctional) Compounds: Versatile Starting Materials for Novel Bis(Heterocycles)

New bis(β-difunctional) compounds could be prepared in good yields. Their utility as intermediates in the synthesis of novel bis(heterocycles) were also investigated.     

Allylic Hydroxylation Through Acid Catalysed Epoxy Ring Opening of Betulinic Acid Derivatives

Acid catalysed epoxy ring opening of several lupane type triterpenoids leads to unusual allylic hydroxylation. The reaction involves the formation of epoxide by m‐chloroperbenzoic acid followed by the treatment of mineral acid. The simple methodology finds utility to introduce a hydroxyl function at the allylic position in these triterpenoids, which is otherwise quite difficult.     

用于电子传输材料的含噻吩环噁二唑衍生物的合成(英文)

在有机电致发光器件研究中,电子传输材料占有特殊重要的地位。但现存的材料存在着不同的缺点。因噁二唑环的高的电子亲和性,噁二唑衍生物是常见的电子传输材料,如:2-(4- 叔丁苯基)-5-联苯基噁二唑(PBD),但容易结晶和低的电子亲和性限制了它的应用。为了得到新的有效的电子传输材料,本文以噻吩为起始反应物经过二碘代、羧酸化、酯化、氨解等步骤合成了噻吩二酰肼,再通过噻吩二酰肼与相应的取代苯甲酰氯缩合、关环的方法将富电子的噻吩环和高电子亲和性的噻吩环同时引入,合成了三种新的含噻吩环噁二唑衍生物2,5-双[2,2’-双(5-取代苯基)-1,3,4-噁二唑]噻吩(R-OXD R=H,OCH_3,CH_3)。同时,采用循环伏安法对其电化学性能进行了测定。这三种化合物都在负方向出现了-对可逆的氧化还原峰,由此得到其电子亲和势(EA)分别为-3.10eV,-3.07eV和-3.08eV,其EA值都高于常用的电子传输材料PBD。R-OXD的高电子亲和势有利于电子从阴极注入。并且由时间渡越法(TOF)测得R-OXD的电子迁移率达到10~(-4)cm~2/V.S(E=10~6V/cm)。所以R-OXD有可能是好的电子传输材料。     

Neuraminic Acid Derivatives as Anti-Influenza Drugs

Influenza types A and B both cause serious disease in man; vaccines are in use but must be reformulated each year in response to antigenic variation and are frequently ineffective against new influenza variants. Influenza viruses are enveloped RNA viruses which contain two major surface glycoproteins: hemagglutinin (HA) and neuraminidase (NA, EC 3.2.1.18). These proteins are essential for infection and offer potential targets for antiviral drug development. Based upon the knowledge of the most important steps of the whole interaction between virus and host cell, the main purpose of our research was to find a sialic acid analogue for increasing the affinity of the sialic acid cell receptor analogue to the principal binding site of HA. A series of sialic acid analogues were prepared and their structures were designed with the goal to have molecules able to saturate the HA receptor and thereby be potentially useful as anti-influenza drugs.     

Liquid Crystalline Thiadiazole Derivatives: Thiadiazole Derivatives Containing Pyridine Ring as Terminal Group

The synthesis and mesomorphic behavior of a new series of liquid crystals containing 1, 3, 4‐thiadiazole and pyridine rings with ‐CH = N‐ central group are reported. All compounds exhibit enantiotropic smectic A mesophase, but the Schiff's base analogues have no mesomorphic behavior. The influence of the pyridine ring and thiadiazole ring is discussed.     

Surfactants as Promising Media for the Preparation of Crystalline Inorganic Materials

Given that surfactants can control the shape and size of micro‐/nanoparticles, they should be able to direct the growth of bulk crystals. This Minireview summarizes recent developments in the application of surfactants for the preparation of new crystalline inorganic materials, including chalcogenides, metal–organic frameworks, and zeolite analogues. The roles of surfactants in different reaction systems are discussed.     

Chromophoric Barbituric Acid Derivatives with Adjustable Hydrogen-Bonding Patterns as Component for Supramolecular Structures

Summary: The barbituric acid moiety of the presented dyes shows multifunctional properties like acidochromism, solvatochromism, and adjustable hydrogen-bonding pattern for molecular recognition. Hydrogen-bonding ability, acidity and solvatochromic effects are studied for a series of N-alkyl substituted 5-(4-nitrophenyl)-barbiturates. Solvatochromism and metal ion complexation are also investigated using chromophoric thiobarbituric acid derivatives.     

Ring Enlargement of Three-Membered Heterocycles by Treatment with In Situ Formed Tricyanomethane

Although the chemistry of elusive tricyanomethane (cyanoform) has been studied during a period of more than 150 years, this compound has very rarely been utilized in the synthesis or modification of heterocycles. Three-membered heterocycles, such as epoxides, thiirane, aziridines, or 2H-azirines, are now treated with tricyanomethane, which is generated in situ by heating azidomethylidene-malonodinitrile in tetrahydrofuran at 45 °C or by adding sulfuric acid to potassium tricyanomethanide. This leads to ring expansion with formation of 2-(dicyanomethylidene)oxazolidine derivatives or creation of the corresponding thiazolidine, imidazolidine, or imidazoline compounds and opens up a new access to these push–pull-substituted olefinic products. The regio- and stereochemistry of the ring-enlargement processes are discussed, and the proposed reaction mechanisms were confirmed by using ¹⁵N-labeled substrates. It turns out that different mechanisms are operating; however, tricyanomethanide is always acting as a nitrogen-centered nucleophile, which is quite unusual if compared to other reactions of this species.     

Polyoxometalates as Inorganic Building Blocks of Multifunctional Molecular Materials

The use of polyoxometalates (pOM's) as inorganic component in the synthesis of new molecular hybrid materials is presented. Here we show that the combination of organic molecules of the tetrathiafulvalene (TTF) type or perylene (per) with POM's yields new radical salts with unprecedented structures that present interesting magnetic and/or electrical properties or coexistence of both. The first true metallic radical salt containing a POM has been prepared and characterized. We also describe the recent results obtained by combining magnetic POM's with the organometallic cation decamethylferrocene.     

Ketene-S,N-Acetals As Synthetic Intermediates of Heterocycles. New Synthesis of Uracil and Barbituric Acid Derivatives

The importance of enamines for organic synthesis is well documented.¹ Ketene-S,N-acetals2 derived from tertiary thioamides are α-alkylthiosubstituted enamines and expected to work as the synthetic equivalent of an enolate anion³. We have been interested in exploring their synthetic utility as the intermediates of heterocycles.⁴     

Poly-Acrylic Acid Derivatives as Diesel Flow Improver for Paraffin-Based Daqing Diesel

Since the diesel products from paraffin-based Daqing crude oil showed low sensitivity to certain commercial diesel pour point depressant (PPDs) that resulted from the high content of paraffin, certain poly-acrylic acid derivatives (PADE) with -COOR, -COOH, -CONHR, and -COO-NH3 R groups by molecular design on the mechanics of diesel; PPDs were synthesized and evaluated as cold flow improver for Daqing 0# diesel in this paper. The pure PADE was superior to the commercial PPDs and displayed a substantial ability of wax crystals dispersion. There was a synergistic effect among the PADE and T1804 and secondary amine. The synergism clearly improved the low temperature performance of Daqing diesel products and could reduce the cold filter plugging point of 0# diesel by 6-7℃.     

Lewis Acid Catalyzed,Selective Cyclopropane‐Ring Opening in Ingol Diterpene Derivatives

Lewis acid mediated skeletal rearrangement of the ingol diterpenoids 1 and 4 via regio‐ and stereospecific cyclopropane‐ring opening afforded the four new compounds 2, 3, 5 , and 6 , named nivulianol A–D (Scheme 1). Their structures were established by means of IR, MS, and in‐depth NMR spectroscopic analyses. The rearranged congeners were tested for lipopolysaccharide (LPS)‐induced prostaglandin (PG) E₂ (cyclooxygenase‐2) inhibition. Thereby, nivulianol B (=(1S*,2E,4R*,5S*,7Z,9S*,11R,13S*,14S*)‐14‐acetoxy‐5‐methoxy‐3,9,13‐trimethyl‐6‐(1‐methylethenyl)‐10‐oxo‐15‐oxatricyclo[9.3.1.0^1,11]pentadeca‐2,7‐dien‐4‐yl (2Z)‐2‐methylbut‐2‐enoate; 3 ) was found to be significantly active, with an IC₅₀ value of 36.3 μg/ml.