Synthesis of Unsymmetrical 1,4-Diketones Via the Michael-Stetter Reaction

The cyanide catalyzed 1,4-Michael addition of aldehydes to α, β-unsaturated ketones has been examined with regard to substituent effects. Adjustment of the donor/acceptor relationship allows for the synthesis of multisubstituted diaryl 1,4-diketones.     

Novel Synthesis of Benzosubstituted Benzofurans Via Diels-Alder Reaction

A useful synthetic approach to benzosubstltuted benzofurans via Diels-Alder reaction of 2-vinyl furans is described.     

Bio-Based Solvent Mediated Synthesis of Dihydropyrimidinthiones Via Biginelli Reaction

Abstract

The three-component Biginelli reaction using aldehyde, thiourea, and 1,3-dicarbonyl compounds was performed smoothly in ethyl lactate (EL) with the catalysis of trimethylsilyl chloride (TMSCl). A class of 3,4-dihydropyrimidinthiones (DHPMs) were synthesized in good to excellent yields via the bio-based solvent mediated catalytic protocol.     

Synthesis via the Mannich Reaction and Biological Activity of Novel Fluorinated Camptothecin Derivatives

Chemistry of Heterocyclic Compounds - Two series of fluorinated camptothecin derivatives had been designed and synthesized via the Mannich reaction. The hexacyclic fluorinated camptothecin...     

Fluorinated Alcohols: Magic Reaction Medium and Promoters for Organic Synthesis

Fluorinated alcohols have been widely used in the synthetic organic chemistry over the past decades. The unique properties such as the strong hydrogen‐bonding donor ability and low nucleophilicity allow them to promote organic reactions in the absence of any catalyst. These approaches have distinct advantages in terms of operational simplicity, practicability and environmental friendliness. Reactions promoted by fluorinated alcohols, including nucleophilic substitution reactions, annulation reactions, electrophilic reactions, dearomatization reactions, functionalization of multiple bond, epoxidation reactions and miscellaneous reactions have been summarized in this account.     

Rethinking Carbohydrate Synthesis: Stereoretentive Reactions of Anomeric Stannanes

In this Concept article, recent advances are highlighted in the synthesis and applications of anomeric nucleophiles, a class of carbohydrates in which the C1 carbon bears a carbon–metal bond. First, the advantages of exploiting the carboanionic reactivity of carbohydrates and the methods for the synthesis of mono- and oligosaccharide stannanes are discussed. Second, recent developments in the glycosyl cross-coupling method resulting in the transfer of anomeric configuration from C1 stannanes to C-aryl glycosides are reviewed. These highly stereoretentive processes are ideally suited for the preparation of carbohydrate-based therapeutics and were demonstrated in the synthesis of antidiabetic drugs. Next, the application of the glycosyl cross-coupling method to the preparation of Se-glycosides and to glycodiversification of small molecules and peptides are highlighted. These reactions proceed with exclusive anomeric control for a broad range of substrates and tolerate carbohydrates with free hydroxyl groups. Taken together, anomeric nucleophiles have emerged as powerful tools for the synthesis of oligosaccharides and glycoconjugates and their future applications will open new possibilities to incorporate saccharides into small molecules and biologics.     

Synthesis and Characterization of Fluorinated Bisphenols and Tetraphenols via a Simple One-Pot Reaction

Fluorinated bisphenols and tetraphenols have been prepared by the condensation reaction of trifluoromethyl activated ketones with simple bisphenols (including catechol, resorcinol, and hydroquinone) catalyzed by trifluoromethanesulfonic acid, in good yields.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Synthesis of Fluorinated Carbohydrates

The similarities in bond length and polarization between C-F and C-OH, as well as the altered hydrogen-bonding properties present in carbohydrates bearing a fluorine atom in place of an hydroxyl group can be exploited in place of an hydroxyl group can be exploited in biochemical investigations (enzyme-carbohydrate interactions, Lectin-carbohydrate affinities, antiobody-carbohydrate binding, etc.). ^1–5 In addition, the different chemistries exhibited by the flourinated carbohydrates have made them important reagents in both metabolic studies and disease diagnosis such as the use of 2-deoxy-2-[18f]-D-fluoroglucose in positron emission tomography. 6,7 Becasue of their widespread utlity, the synthesis of fluorinated carbohydrates is of importance. However, the Introduction of fluorine into a carbohydrate moiety can be an arduous task because of (1) the protection and deprotection steps required to set up the desired hydroxyl group for the introduction of fluoride, (2) the low nucleophilicity fo fluoride ion, and (3) fluoride ion catalyzed elimination reactions. 8,9 The search for Milder and more selective methods for the introduction of fluorine into Carbohydrates has continued at a rapid pace and it is appropriate to review som of the recent results.     

氟代糖的合成

本文综述了氟代糖合成的新进展及利用选择性氟化合成具有生物活性的物质。     

Michael Addition Reaction of Fluorinated Nitro Compounds

The Michael addition reactions of fluorinated nitro compounds with electron deficient olefins to give γ‐fluoro‐γ‐nitro‐esters, nitriles and ketones which bear a fluorinated quaternary carbon center were reported. The reactions were promoted by TMG, affording the desired adducts in acceptable to good yields.     

Mechanochemical Synthesis of Fluorinated Imines

A number of imines, including 12 new compounds, previously not reported in the literature, derived from variously fluorinated benzaldehydes and different anilines or chiral benzylamines were synthesized by a solvent-free mechanochemical method, which was based on the manual grinding of equimolar amounts of the substrates at the room temperature. In a very short reaction time of only 15 min, the method produced the expected products with good-to-excellent yields. The yields were comparable or significantly higher than those reported in the literature for the imines synthesized by other methods. Importantly, the conditions used for the reactions with aniline derivatives also resulted in the high yields of imines obtained from chiral benzylamines, and can be extended to the synthesis with other similar amines. Structures of all imines were confirmed by NMR spectroscopy: ¹H, ¹³C and ¹⁹F. For four compounds, X-ray structures were also obtained. The synthetic approach presented in this paper contributes to the prevention of environmental pollution and can be easily extended for larger-scale syntheses. The mechanochemical solvent-free method provides a convenient strategy particularly useful for the preparation of fluorinated imines being versatile intermediates or starting material in the synthesis of drugs and other fine chemicals.     

Synthesis of Chiral alpha,delta-Dioxygenated Allylic Stannanes as Reagents for Carbohydrate Synthesis and Homologation

The delta-oxygenated allylic stannanes 4.4 and 4.5, prepared through addition of Bu(3)SnLi to gamma-OTBS crotonaldehyde 4.3c followed by etherification of the adduct with TBS-Cl or MOM-Cl, undergo transmetalation with InCl(3) and in situ addition to aldehydes leading to mainly anti adducts 5.1 or 5.2, accompanied by varying amounts of syn diastereomers. Selectivities of >95:5 can be realized with the MOM reagent 4.5 and ynals 4.3d and 4.3e or cyclohexanecarboxaldehyde 4.3a. With enals 4.3b and 4.3c, 80:20 mixtures of anti and syn adducts are formed. The S enantiomer 10.1 of stannane 4.5 has also been prepared as a reagent for carbohydrate synthesis. Accordingly, addition to alpha-ODPS acetaldehyde 10.2 in the presence of InCl(3) leads to the adduct 10.3 as an inseparable 90:10 mixture of anti and syn diastereomers. Dihydroxylation of the OTBS derivative 10.4 affords the potential altrose precursor 10.5 in 81% yield.     

氟代有机硅化合物的合成新方法

本工作利用CuCl/HOC₂H₄NH₂催化剂,将1,2-二溴四氟乙烷与烯基有机硅化合物进行加威反应,制备了一系列新的含氟有机硅化合物,并进行了分析鉴定。对影响反应的诸因素做了初步探讨。     

几个新型含氟化合物的合成

以3-硝基-4-氯三氟甲苯(1)为起始原料, 合成了新型含氟杂环化合物8和3个含氟中间体4, 5, 6. 通过IR, NMR, MS和元素分析对它们的结构进行了表征. 探讨了反应条件对产物结构的影响, 提出了化合物4可能的形成机理.     

Synthesis of New Fluorinated Podophyllotoxin Derivatives

Five fluorinated podophyUotoxin derivatives were synthesized using dimethylamino-sulfurtrifluoride (DAST).     

含氟聚合物的合成进展

含氟聚合物由于其优异的化学和物理性能以及广泛的应用前景而受到关注。根据聚合反应单体结构不同,可以通过不同方法合成各种结构的含氟聚合物。这些聚合方法主要是可控／“活性”聚合,例如：原子转移自由基聚合（ATRP）、原子转移自由基一乙烯基自缩合聚合（ATR—SCVP）、可逆加成一断裂链转移聚合（RAFT）、氮氧稳定自由基聚合...