二茂铁偶姻衍生物前体——2-二茂铁基-2-(芳基羟甲基)-1,3-二噻烷的合成

用2-二茂铁基-1,3-二噻烷的锂代物与芳基羰基化合物的反应,合成了16种2-二茂铁基-2-(芳基羟甲基)-1,3-二噻烷.简要讨论了产物的¹HNMR谱以及羰基化合物结构对反应的影响.     

Über einen neuen Zugang zu Imidazolen,sowie deren Verwendung zur Synthese von Purinen und 4,6-Dihydro-1,2-dimethyl-8-phenylimidazo[4,5-e]-1,4-diazepin-5(1H)-on

A novel route to imidazoles and their use for the synthesis of purines and 4,6-dihydro-1,2-dimethyl-8-phenylimidazo[4,5-e]-1,4-diazepin-5(1H)-on. Recently it has been shown [2] that pyrimidines are available from Thorpe-Ziegler cyclization of the appropriate dinitriles. As an extension of this work, a novel route to imidazoles has been developed. It has been demonstrated that these imidazole derivatives are valuable intermediates for the synthesis of purines by application of standard procedures. The use of these imidazoles has enabled the preparation of some derivatives not accessible by other methods.     

Gas Phase Formation of the Interstellar Molecule Methyltriacetylene

Methyltriacetylene – the largest methylated polyacetylene detected in deep space – has been synthesized in the gas phase via the bimolecular reaction of the 1-propynyl radical with diacetylene under single-collision conditions. The barrier-less route to methyltriacetylene represents a prototype of a polyyne chain extension through a radical substitution mechanism and provides a novel low temperature route, in which the propynyl radical piggybacks a methyl group to be incorporated into methylated polyynes. This mechanism overcomes a key obstacle in previously postulated reactions of methyl radicals with unsaturated hydrocarbon, which fail the inclusion of methyl groups into hydrocarbons due to insurmountable entrance barriers thus providing a fundamental understanding on the electronic structure, chemical bonding, and formation of methyl-capped polyacetylenes. These species are key reactive intermediates leading to carbonaceous nanostructures in molecular clouds like TMC-1.     

Eine Synthese von Bicyclo[10.3.0]pentadec-1(12)-en-13-on und seinem 14-Methylderivat

A Synthesis of Bicyclo[10.3.0]pentadec-1(12)-en-13-one and its 14-Methyl Derivative. A new route to bicyclo[10.3.0]pentadec-1(12)-en-13-one ( 2 ) and its 14-methyl derivative 3 – useful intermediates in the synthesis of cyclopentadecanone ( 4 = exaltone®) and rac-muscone ( 5 ) – is described.     

2-Substituted-3,7-dinitro-11-oxatricycloundec-9-ene: an approach towards the synthesis of Ergot alkaloids

A simple and versatile method for the preparation of various ergoline or secoergoline skeleton, using 2-substituted-3,7-dinitro-11-oxatricycloundec-9-ene as key intermediates, is described. The key step involves an IMDAF reaction with an excellent stereocontrol. This novel synthetic route provides new cycloadducts as useful scaffolds for Ergot alkaloids synthesis.     

Alkylation of magnesium sulfinates: a direct transformation of functionalized aromatic/heteroaromatic halides into sulfones

[reaction: see text] Sulfinate alkylation is one of the conventional methods for sulfone synthesis. The alkylation of magnesium sulfinates, which are easily accessible via reactions of organomagnesium intermediates with sulfur dioxide, provides a convenient route for sulfone preparation. In this communication, we report a preliminary study of the alkylation of arylmagnesium sulfinates. An application of this reaction to directly transform functionalized aromatic/heteroaromatic halides into sulfones is also described.     

Xanthone natural products via N-heterocyclic carbene catalysis: total synthesis of atroviridin

The total synthesis of atroviridin has been accomplished by a linear route involving the N-heterocyclic carbene (NHC)-catalyzed aroylation of the fluorobenzene derivative, Claisen cyclization of the O-propargylated benzophenones, and intramolecular 1,4-addition of the quinone intermediates. The result provides a viable route to xanthone natural products.     

Electric Field Enhanced Ammoxidation of Aldehydes Using Supported Fe Clusters Under Ambient Oxygen Pressure

Heterogeneous catalytic ammoxidation provides an eco-friendly route for the cyanide-free synthesis of nitrile compounds, which are important precursors for synthetic chemistry and pharmaceutical applications. However, in general such a process requires high pressures of molecular oxygen at elevated temperatures to accelerate the oxygen reduction and imine dehydrogenation steps, which is highly risky in practical applications. Here, we report an electric field enhanced ammoxidation system using a supported Fe clusters catalyst (Fe/NC), which enables efficient synthesis of nitriles from the corresponding aldehydes under ambient air pressure at room temperature (RT). A synergistic effect between the external electric field and the Fe/NC catalyst promotes the ammonia activation and the dehydrogenation of the generated imine intermediates and avoids the unwanted backwards reaction to aldehydes. This electric field enhanced ammoxidation system presents high efficiency and selectivity for the conversion of a series of aldehydes under mild conditions with high durability, rendering it an attractive process for the green synthesis of nitriles with fragile functional groups.     

A solid-supported,enantioselective synthesis suitable for the rapid preparation of large numbers of diverse structural analogues of (-)-saframycin A

A 10-step solid-supported, enantioselective synthesis suitable for the rapid preparation of large numbers of diverse structural analogues of saframycin A is described. The synthetic route, which bears analogy to solid-phase peptide synthesis, involves the directed condensation of N-protected alpha-amino aldehyde reactants. A novel dual linker was developed for attachment of intermediates to the solid support via a C-protective group, a substituted morpholino nitrile derivative. The route employs a novel diastereospecific cyclorelease mechanism, supports structural variation at multiple sites in the saframycin core, and obviates the need for chromatographic purification of the products or any intermediate. To demonstrate the feasibility of structural variation at multiple sites, a matrix of 16 saframycin A analogues was prepared by parallel synthesis with simultaneous variation of two sites. This work is notable not only as a preliminary step toward large-scale library construction but also as an example of the use of sequential stereoselective C-C bond-forming reactions on the solid phase for the preparation of natural product analogues.     

A facile and efficient method for the synthesis of solasodine from diosgenin

A facile and high-yielding route for the synthesis of solasodine from diosgenin is devised. Ring opening of steroidal spiroketal under mild conditions with trifluoroacetyl trifluoromethanesulfonate (TFAT) provides an applicable protocol to prepare key intermediates 4 or 3-Ac-solasodine, which can potentially serve as a platform for the selective functionalization of C(3)-OH and N-H of solasodine. The simple operations without purification by column chromatography make this method suitable to scale up.     

A Convenient Route for the Preparation of Aromatic Aldehydes

Though a variety of methods^2–5 are available for the synthesis of aldehydes, this area continues to attract attention^6,7 since aldehydes are important intermediates in synthetic organic chemistry. In this communication we present a new route for the synthesis of aromatic aldehydes.     

Vinylmetalloids : II. The high regioselectivity of dialkylboranes in the hydroboration of vinyltrimethylsilane

Dialkylboranes such as disiamylborane, dicyclohexylborane and 9-borabicyclo[3.3.1]nonane add cleanly to vinyltrimethylsilane (I) with high regiospecificity (? 95%) to give the corresponding β-silylethylboranes, valuable intermediates in the synthesis of functionalized organosilanes. Oxidation of these adducts provides a convenient, high-yield route to 2-trimethylsilylethanol (IIβ). Reduction of acetyltrimethylsilane (IX) with borane-tetrahydrofuran provides a simple route to the isomeric 1-trimethylsilylethanol (IIα). These new developments illustrate the utility of borane reagents in the regiospecific syntheses of trimethylsilylethanols (II).     

Understanding the Synthesis Kinetics of Single-Crystal Co-Free Ni-Rich Cathodes

Non-equilibrium kinetic intermediates are usually preferentially generated instead of thermodynamic stable phases in the solid-state synthesis of layered oxides. Understanding the inherent complexity between thermodynamics and kinetics is important for designing high cationic ordering cathodes. Single-crystal strategy is an effective way to solve the intrinsic chemo-mechanical problems of Ni-rich cathodes. However, the synthesis of high-performance single-crystal is very challenging. Herein, the kinetic reaction path and the formation mechanism of non-equilibrium intermediates in the synthesis of single-crystal Co-free Ni-rich were explored. We demonstrate that the formation of non-equilibrium intermediate and the electrochemical-thermo-mechanical failure can be effectively inhibited by driving low-temperature topotactic lithiation. This work provides a basis for designing high-performance single-crystal Ni-rich layered oxides by regulating the defective structures.     

4-苯胺喹唑啉类化合物合成研究进展

4-苯胺喹唑啉类化合物是一类具有广泛药理活性的喹唑啉类生物碱,在酪氨酸激酶受体(EGFR)抑制剂的研发中具有重要的作用。已经上市的此类药物有吉非替尼(gefitinib)和厄洛替尼(erlotinib)等。此类化合物的合成都是经过喹唑啉酮中间体或直接环合成4-苯胺喹唑啉。苯甲醛及其衍生物被用作反应原料,两种合成路线都要经历对苯甲醛的硝化及硝基的还原两步反应。笔者经查阅资料,设计并验证了以苯胺为原料、经靛红中间体得到4-苯胺喹唑啉类化合物的新的合成路线。本文依据这两种合成策略综述了4-苯胺喹唑啉类化合物的合成方法,并对各种方法的优缺点进行了总结,为进一步研究4-苯胺喹唑啉合成及设计具有药理活性的新化合物提供参考。     

Solid-phase synthesis of alkanethiols for the preparation of self-assembled monolayers

Self-assembled monolayers (SAMs) of alkanethiols (ATs) on gold can be used to fabricate surfaces for nanoscience and biology. The chemical structure of the interface can be tailored simply by modifying the AT headgroup. To streamline access to different precursor ATs, we developed a general solid-phase synthetic route. A key feature of this route is the use of a modified resin containing an AT linker ("AT resin") because it minimizes purification steps. The precursor to the AT resin was prepared in five steps, and all of the synthetic intermediates are stable solids that can be purified by crystallization. Accordingly, the AT resin can be prepared on a multigram scale. The utility of the AT resin was evaluated by using it to generate a variety of ATs. For example, ATs presenting different types of integrin-binding ligands (linear and cyclic RGD derivatives) were prepared and used to form arrays of SAMs that support cell adhesion. Additionally, the AT resin also provides a starting point for the synthesis of ATs presenting reactive groups (e.g., an amine-reactive AT or a maleimide-containing alkanedisulfide) or protein immobilization tags (e.g., biotin-AT). Thus, our synthetic strategy provides a convenient and flexible means for the synthesis of the necessary building blocks for custom SAMs and SAM arrays.     

Photoaddition with 1,2-bis(trimethylsiloxy)cyclobutene: a versatile entry to the stereocontrolled total synthesis of various sesquiterpenes and diterpenes

The photocycloaddition of 2-cyclohexenones to 1,2-bis(trimethyl-siloxy)cyclobutene provides a short and versatile route to adequately functionalized decalins for the total synthesis of members of the following terpene classes: the eudesmanes, the eudesmanolides, the guaianes, the labdanes and the nagilactones. Regioselective and stereoselective manipulation of these key intermediates is discussed.     

Synthetic studies toward the cytotoxic norditerpene (+)-harringtonolide: setting up key-stereogenic centers of the cyclohexane ring D

The pivotal stereogenic centers of the asymmetric cycle D of (+)-harringtonolide were installed by functionalization of an enantiomerically pure IMDA cycloadduct, constructed from the chiral pool. The chiral 1,3-dioxane template used to direct the IMDA reaction was unraveled in an acidic medium, through spectacular hydrolysis of the acetal and concomitant lactone ring contraction. The central cyclohexene was selectively epoxidized either on the β- or on the α-side depending on the substitution pattern. The reactivity of several epoxide intermediates was challenged toward the construction of the oxygenated bridges of harringtonolide. We found one of them suitable for an access to another natural product, tetrodecamycin, which shares a similar substitution pattern as harringtonolide. Alternatively, functionalization led to set up key-stereocenters, en route to the asymmetric total synthesis of harringtonolide. The reactivity of the epoxide intermediates gave helpful insight for future work on this total synthesis.     

乙酸/氧气法高效合成取代卟啉

卟啉在结构上可视为是由4个吡咯类亚甲基的α-碳原子通过次甲基桥互联而形成的大分子杂环化合物,具有高度共轭结构。 随着卟啉与金属的配合物即金属卟啉的催化特性受到广泛关注,取代卟啉的高效合成日益显示出重要的学术和应用价值。 但是现有的丙酸法和乙酸/硝基苯法存在卟啉收率低、环境污染严重等问题,导致取代卟啉的成本居高不下,限制了其广泛应用。 本文利用乙酸/氧气法,在120 ℃下控制反应物浓度为0.24 mol/L,并在反应第一阶段(前30 min)通入氧气,得到四(4-溴苯基)卟啉(化合物d),产率高达53.8%。 该方法是高效合成取代卟啉的新方法,卟啉骨架形成和氧化两个反应同时进行,方法简单、绿色且收率高,有望大幅度降低取代卟啉的合成成本。     

Reaction of β-lactam carbenes with alkyl isonitriles for a ready approach to 4-cyano and 4-carbamoyl substituted β-lactams

The reaction of β-lactam carbenes with alkyl isonitriles was investigated. Two different types of products, 4-cyano- or 4-carbamoyl-β-lactams, were isolated, depending upon the nature of the alkyl group of the isonitriles. The cyano-β-lactams were derived by a N-to-C 1,3-rearrangement of the ketenimine intermediates, while the carbamoyl-β-lactams were the hydrolysis products of the intermediates. This work extends the application of β-lactam carbenes, and provides a very simple and efficient route to 4-cyano- or 4-carbamoyl-β-lactams, which are versatile synthetic intermediates and new chemical entities of potential biological activity.     

Enantioselective Staudinger synthesis of beta-lactams catalyzed by a planar-chiral nucleophile

The development of efficient methods for the stereoselective generation of beta-lactams is an important goal, due to their biological activity and their utility as synthetic intermediates. The Staudinger reaction, an overall [2 + 2] cycloaddition of a ketene with an imine, provides a nicely convergent route to this family of compounds. Nearly all studies to date of asymmetric variants of the Staudinger reaction have focused on the use of chiral auxiliaries to control the stereochemistry of the beta-lactam. In this report, we establish that a planar-chiral derivative of 4-(pyrrolidino)pyridine serves as a very effective enantioselective catalyst for the Staudinger beta-lactam synthesis, coupling a range of symmetrical and unsymmetrical ketenes with an array of imines with very good stereoselection and yield.