Photoinduced electron transfer chemistry of phthalimdes: an efficient tool for CC-bond formation

A collection of intra- and intermolecular photoinduced electron transfer (PET) reactions is presented which all are based on the phthalimide chromophore as the oxidizing species. Electron-donating groups versatile for PET processes are ethers, thioethers, amines, alkenes, arenes, and carboxylates as well as α-trialkylsilyl activated heteroatom-substituents. These reactions can be efficiently applied for the synthesis of five- and six-membered ring heterocycles, medium-sized and macrocyclic products such as macrolides, cyclopeptides, crown ethers or thioethers as well as (from intermolecular processes) Grignard-alike products.     

Palladium-Catalyzed Allylic C-OH Functionalization for Efficient Synthesis of Functionalized Allylsilanes

A new method is described for palladium-catalyzed allylic silylation using allylic alcohols and disilanes as precursors. The reactions proceed smoothly under mild and neutral conditions, and this method is suitable for synthesis of regio- and stereodefined allylsilanes. The presented silylation reaction can be easily extended to include synthesis of allylboronates by change of the dimetallic reagent. The presented synthetic procedure offers a broad platform for the selective synthesis of functionalized allyl metal reagents, which are useful precursors in advanced organic chemistry and natural product synthesis.     

Preparative solid state chemistry. Recent developments

A survey of recent developments in preparative solid state chemistry shows that, with a knowledge of structural chemistry and reactivity patterns of solids, it is possible to synthesize a variety of new solids possessing novel structures. A distinction is made between synthesis ofnew solids and synthesis of solids bynew methods. Three new routes to solid state synthesis are recognized: the precursor method, and topochemical methods involving redox and ion-exchange reactions. The low-temperature topochemical methods enable synthesis of metastable phases that are inaccessible by the high temperature route. Several illustrative examples of solid state synthesis from the recent literature are presented.     

不对称催化反应在手性农药不对称合成中的一些应用

近十多年来，不对称催化反应在单一手性农药研发中的应用渐渐引起人们的关 注，结合自己的研究对这一领域的不对称催化反应及手性催化剂的发展进行了归纳 总结。     

Reaction path synthesis methodology for waste minimization

Being the core of whole process, a chemical process is a key step for reducing waste generation. Therefore, to organize a reasonable reaction path is very important for reducing waste emission. Because of the large amount of the feasible reaction path and other factors in a chemical reaction system, the opti-mizing for reaction path is difficult. Since the reaction path synthesis problem has presented, lots of re-searchers focused on it. At the beginning, only chem-ists took the research work,…     

微波干介质反应

微波干介质反应是一门新兴的绿色化学合成技术,已成功地应用于多种有机反应。运用微波干介质反应技术进行一步法或多组分反应研究是当前库合成的研究热点。无溶剂反应具有成本低、操作简便、选择性好等优点,是绿色化学的重要研究方向之一。本文主要介绍了官能团的转化、氧化、还原、杂环化合物的合成、缩合及多组分反应等微波干介质反应。     

有机合成的新世纪――－有机合成近年进展鉴赏

本文简要介绍了2005年至今有机合成领域的进展,第一部份有机合成方法学的一些新进展中突出介绍了金属参与的有机合成反应、自由基介导的合成反应、"一个反应瓶"内的多步反应以及不对称反应四个方面;第二部份复杂天然产物全合成则以10个分子的为例介绍这方面的进展。     

Reactions of Organometallic Reagents with Halogenophosphazene Cyclic Trimers,Tetramers, and High Polymers

Abstract

Three main mechanistic pathways are now evident when Grignard, organolithium, organocopper, or transition metal anions are used as reagents for reactions with halogeno-phosphazenes-substitution, metal-halogen exchange, and skeletal cleavage. Use of these reaction pathways allows the synthesis of species such as I-X. A general mechanistic theory of these reactions is presented, together with an application of these mechanisms to macromolecular synthesis.     

Metathesis cascade strategies (ROM-RCM-CM): a DOS approach to skeletally diverse sultams

The development of a ring-opening metathesis/ring-closing metathesis/cross-metathesis (ROM-RCM-CM) cascade strategy to the synthesis of a diverse collection of bi- and tricyclic sultams is reported. In this study, functionalized sultam scaffolds derived from intramolecular Diels-Alder (IMDA) reactions undergo metathesis cascades to yield a collection of tricyclic sultams. Additional appendage-based diversity was achieved by utilizing a variety of CM partners.     

Decarbonylative C-C bond forming reactions mediated by transition metals

New methods for carbon-carbon (C-C) forming reactions are constantly emerging in the field of organic synthesis. In this review, a brief history followed by recent developments of decarbonylative C-C forming reactions mediated by transition metals is described. Many different substrates are presented and the review is organized by the different carbonyl precursors, such as acyl chlorides, aldehydes, anhydrides, esters and ketones, used in the respective transformations. Furthermore, the broad scope of these reactions is exhibited by the application to several reaction types (e.g. Heck-type reactions, Suzuki cross-coupling type reactions, C-H activation, etc.) as well as a natural product synthesis (e.g. muscroride A). While several examples are provided, this review marks the beginning of a new field that is still in its infancy and for what might be a new approach to achieve highly efficient reactions that come closer to meeting the standards of chemical economies (e.g. atom, redox, step, etc.) and green chemistry.     

Improving the Stability of Maleimide–Thiol Conjugation for Drug Targeting

Maleimides are essential compounds for drug conjugation reactions via thiols to antibodies, peptides and other targeting units. However, one main drawback is the occurrence of thiol exchange reactions with, for example, glutathione resulting in loss of the targeting ability. A new strategy to overcome such retro-Michael exchange processes of maleimide–thiol conjugates by stabilization of the thiosuccinimide via a transcyclization reaction is presented. This reaction enables the straightforward synthesis of stable maleimide–thiol adducts essential in drug-conjugation applications.     

Nitroxides: applications in synthesis and in polymer chemistry

This Review describes the application of nitroxides to synthesis and polymer chemistry. The synthesis and physical properties of nitroxides are discussed first. The largest section focuses on their application as stoichiometric and catalytic oxidants in organic synthesis. The oxidation of alcohols and carbanions, as well as oxidative C-C bond-forming reactions are presented along with other typical oxidative transformations. A section is also dedicated to the extensive use of nitroxides as trapping reagents for C-centered radicals in radical chemistry. Alkoxyamines derived from nitroxides are shown to be highly useful precursors of C-centered radicals in synthesis and also in polymer chemistry. The last section discusses the basics of nitroxide-mediated radical polymerization (NMP) and also highlights new developments in the synthesis of complex polymer architectures.     

Diversity through a branched reaction pathway: generation of multicyclic scaffolds and identification of antimigratory agents

A library of 91 heterocyclic compounds composed of 16 distinct scaffolds has been synthesized through a sequence of phosphine-catalyzed ring-forming reactions, Tebbe reactions, Diels-Alder reactions, and, in some cases, hydrolysis. This effort in diversity-oriented synthesis produced a collection of compounds that exhibited high levels of structural variation both in terms of stereochemistry and the range of scaffolds represented. A simple but powerful sequence of reactions thus led to a high-diversity library of relatively modest size with which to explore biologically relevant regions of chemical space. From this library, several molecules were identified that inhibit the migration and invasion of breast cancer cells and may serve as leads for the development of antimetastatic agents.     

Intrinsic Kinetics of Dimethyl Ether Synthesis from Syngas

The intrinsic kinetics of dimethyl ether (DME) synthesis from syngas over a methanol synthesis catalyst mixed with methanol dehydration catalyst has been investigated in a tubular integral reactor at 3-7MPa and 220-260℃. The three reactions including methanol synthesis from CO and H2, CO2 and H2, and methanol dehydration were chosen as the independent reactions. The L-H kinetic model was presented for dimethyl ether synthesis and the parameters of the model were obtained by using simplex method combined with genetic algorithm. The model is reliable according to statistical analysis and residual error analysis. The synergy effect of the reactions over the bifunctional catalyst was compared with the effect for methanol synthesis catalyst under the same conditions based on the model. The effects of syngas containing N2 on the reactions were also simulated.     

Inferring Minimal Feasible Metabolic Networks of <Emphasis Type="Italic">Escherichia coli</Emphasis>

Since the organism contains many redundant reactions, the minimal feasible metabolic network that contains the basic growth function is not the collection of reactions that associate the essential genes. To identify minimal metabolic reaction set is a challenging work in theoretical approach. A new method is presented here to identify the smallest required reaction set of growth-sustaining metabolic networks. The content and number of the minimal reactions for growth are variable in different random processes. Though the different carbon sources also vary the content of the reactions in the minimal metabolic networks, most essential reactions locate in the same metabolic subsystems, such as cofactor and prosthetic group biosynthesis, cell envelope biosynthesis, and membrane lipid metabolism.     

Amidocarbonylation-An Efficient Route to Amino Acid Derivatives

Atom efficient, multicomponent reactions that lead to high-value products from inexpensive starting materials are of both economic and ecological interest for industrial organic synthesis. alpha-Amino acids are amongst the most important compounds in chemistry and biology. As well as their biochemical significance as building blocks of peptides and proteins, alpha-amino acids are also becoming increasingly interesting as fine chemicals. Possibly one of the key reactions in the preparation of these compounds is transition metal catalyzed amidocarbonylation, where the alpha-amino acid framework is constructed in a single step from an aldehyde, an amide, and carbon monoxide. This article gives a current overview of transition metal catalyzed amidocarbonylation reactions used in the synthesis of alpha-amino acids derivatives. A classification and summary of the significant features of this three component reaction is first presented together, with an historical introduction. This section is followed by two sections on cobalt- and palladium-catalyzed amidocarbonylation. A discussion of the mechanism of each of the different amidocarbonylation variants form an introduction. Overviews on further synthetic development of the methodology, such as the domino reaction with an amidocarbonylation step and the expansion of the range of starting materials, form the main topics of both variants. The potential of the method is demonstrated with the help of examples of special synthetic utility (for example, the preparation of arylglycines). Finally, possibilities for future developments in transition metal catalyzed amidocarbonylation reactions are proposed on the basis of the current state of knowledge.     

Recent Progress in Enzymatic Synthesis of Sugar Nucleotides

Glycosylation is one of the most important reactions in nature as it results in the formation of glycoconjugates with diverse biological functions. Sugar nucleotides serve as the natural donor molecules for the biosynthesis of such glycoconjugates and other carbohydrates. Furthermore, these donor molecules are also indispensable building blocks for the enzymatic synthesis of carbohydrates in vitro using Leloir-type glycosyltransferases. Given such importance, the biosynthetic pathways of sugar nucleotides have been exploited, enabling the development of both chemical and enzymatic approaches to produce these molecules. A survey of recent progress in enzymatic synthesis of common mammalian sugar nucleotides as well as their derivatives is thus presented. As a popular strategy, conjugation of sugar nucleotide synthesis with glycosyltransfer reactions and in vivo production of sugar nucleotides are also included.     

Synthesis of beta-amino acids based on oxidative cleavage of dihydropyridone derivatives

[reaction: see text] A new method for the synthesis of beta-amino acids based on 2,3-dihydropyridones as starting materials is presented. Conversions of 2,3-dihydropyridones with NaIO4 and subsequently with base gave the corresponding beta-amino acids in a one-pot procedure. The reactions have been monitored by 1H NMR indicating that the beta-amino acids were formed in quantitative yields mostly. This method appears to be of broad scope, as 2-substituted 2,3-dihydropyridones are easily accessible via N-acyliminium ions generated from 4-methoxypyridine.     

Suzuki-Miyaura and Stille reactions as key steps in the synthesis of diversely functionalized Amaryllidaceae alkaloid analogs bearing a 5,6,7,8-tetrahydrobenzo[c,e]azocine skeleton

Microwave-assisted Suzuki-Miyaura and Stille cross-coupling reactions for the synthesis of highly electron-rich and diversely functionalized biaryl intermediates are presented. Microwave-irradiation has been demonstrated to be a very powerful tool for performing difficult transition metal-catalyzed cross-coupling reactions with unfavorably substituted coupling partners. The key biaryl intermediates were used for the microwave-enhanced construction of the 5,6,7,8-tetrahydrobenzo[c,e]azocine skeleton of the Apogalanthamine analogs. The success of the strategy is demonstrated by synthesizing a number of hitherto unknown, diversely functionalized, natural product analogs.     

Rapid On-Chip Synthesis of Complex Glycomimetics from N-Glycan Scaffolds for Improved Lectin Targeting

C-type lectin receptor (CLR) carbohydrate binding proteins found on immune cells with important functions in pathogen recognition as well as self and non-self-differentiation are increasingly moving into the focus of drug developers as targets for the immune therapy of cancer autoimmune diseases and inflammation and to improve the efficacy of vaccines. The development of molecules with increased affinity and selectivity over the natural glycan binders has largely focused on the synthesis of mono and disaccharide mimetics but glycan array binding experiments have shown increased binding selectivity and affinity for selected larger oligosaccharides that are able to engage in additional favorable interactions beyond the primary binding site. Here, a platform for the rapid preparation and screening of N-glycan mimetics on microarrays is presented that turns a panel of complex glycan core structures into structurally diverse glycomimetics by a combination of enzymatic glycosylation with a nonnatural donor and subsequent cycloaddition with a collection of alkynes. All surface-based reactions were monitored by MALDI-TOF MS to assess conversion and purity of spot compositions. Screening the collection of 374 N-glycomimetics against the plant lectin WFA and the 2 human immune lectins MGL ECD and Langerin ECD produced a number of high affinity binders as lead structures for more selective lectin targeting probes.