Highly diastereoselective Friedel-Crafts reaction of furans with 8-phenylmenthyl glyoxylate

The Friedel-Crafts reaction of (1R)-8-phenylmenthyl glyoxylate with variously substituted furans was found to be efficiently promoted by SnCl(4) or magnesium salts with high diastereoselectivities. MgBr(2) performs especially well under simple, undemanding conditions, giving both high yields and high diastereoselectivities (>90%). The reaction afforded chiral substituted furan-2-yl-hydroxyacetic acid esters, compounds of potentially high synthetic interest. [reaction: see text]     

Catalytic, asymmetric, "interrupted" Feist-Bénary reactions

Pyrimidine derivatives of the cinchona alkaloids function as excellent asymmetric catalysts for the "Interrupted" Feist-Bénary Reaction. This reaction produces highly substituted hydroxydihydrofurans from simple starting materials under mild conditions. The asymmetric reaction gives high enantioselectivities with unsubstituted bromoketones, and high enantio- and diastereoselectivities with substituted substrates. Mechanistic experiments suggest that the hydrobromide salt of the alkaloid derivative is the active catalyst for the reaction.     

Synthese funktionell substituierter Disilane auf der Basis von Triflatderivaten

Synthesis of Functional Substituted Disilanes on the Basis of Triflate Derivatives Functional substituted disilanes are prepared by reaction of phenylated disilanes with trifuloromethanesulfonic acid. Reduction of the triflate derivatives with LiAlH₄ leads to Si? H substituted disilanes. The chlorinated disilanes are obtained by reaction of the triflate derivatives with Et₃NHCl. Chloro-hydrogen substituted disilanes are prepared by combination of both reaction types. The preparation of these compounds in a high purity is difficult on other ways.     

An efficient and environmentally friendly DABCO catalyzed Henry reaction of isatins

An efficient and general method has been described for the synthesis of 3-hydroxy-3-(nitromethyl)indolin-2-one by the reaction of isatins with nitromethane/nitroethane in the presence of DABCO. The reaction is catalytic, very rapid, yields are very high and avoids the use of solvents for reaction. The protocol is applicable for substituted isatins as well as substituted nitroalkanes.     

Chiral Allenes via Alkynylogous Mukaiyama Aldol Reaction

Herein we describe the development of a catalytic enantioselective alkynylogous Mukaiyama aldol reaction. The reaction is catalyzed by a newly designed chiral disulfonimide and delivers chiral allenoates in high yields and with excellent regio‐, diastereo‐, and enantioselectivity. Our process tolerates a broad range of aldehydes in combination with diverse alkynyl‐substituted ketene acetals. The reaction products can be readily derivatized to furnish a variety of highly substituted enantiomerically enriched building blocks.     

Synthesis of new substituted cylopentenone derivatives via a one-pot three-component reaction between arylglyoxals,acetylacetone, and amines in aqueous media

An efficient one-pot method for the synthesis of new substituted cylopentenone derivatives is described via reaction of arylglyoxals and acetylacetone with aliphatic amines. This reaction was carried out in aqueous media in the absence of any catalyst or promoter to produce substituted cylopentenone in high yield.     

One-pot synthesis of vinylisoxazolidines from simple hydroxylamines and conjugated carbonyls

Herein is reported the highly chemo- and regioselective synthesis of 3-vinyl-4-formyl and 3-vinyl-5-formylisoxazolidines from enals, hydroxylamines and dipolarophiles under thermal conditions. The reaction works in high yields for a large array of substituted enals and a variety of dipolarophiles. The reaction provides the respective isoxazolidines with high chemoselectivity, stereospecificity and diastereoselectivity without significant purification. The substitution pattern on the dipolarophile directs the regioselectivity of the reaction to provide either 3,4- or 3,5-substituted isoxazolidine isomers. This method provides access to a wide variety of highly substituted, stereochemically dense isoxazolidine scaffolds from the selective reaction of the three proposed components.     

Simple and practical synthesis of pyrano- and furano[3,2-c]-quinoline derivatives under non-Lewis acid catalysis

One-pot synthesis of substituted pyrano- and furano[3,2-c]quinoline derivatives from appropriately substituted anilines, substituted benzaldehydes and dienophiles via Povarov reaction catalyzed by HCl-ethanol were reported.Good to excellent yields with high diastereoselectivity were obtained in all entries tested.     

Organocatalytic Formation of Chiral Trisubstituted Allenes and Chiral Furan Derivatives

A novel reaction that provides chiral allenes by amino catalytic activation of either aldehydes or α,β‐unsaturated aldehydes for reaction with alkynyl‐substituted enones is presented. The reaction forms a variety of trisubstituted allenes in high yields and with excellent stereoselectivities. The utility of the reaction concept is demonstrated by the synthesis of chiral furan derivatives in high yields and stereoselectivities.     

双酰基脲化合物的合成研究

研究了双酰基脲化合物的制备方法-芳酰基异氰酸酯与呋喃甲酰胺之间的亲核加成反应，制得5个未见报道的N-取代苯甲酰基-N'-5-取代苯基-2-呋喃甲酰基脲，结构均经^1H NMR、IR、元素分析确证。     

Chemoselective reactions of amidines: selective formation of iminopyrimidine regioisomers

The dramatic effect of base on the chemoselectivity of the reaction of amidines with substituted 3-phenyl-2-propynylnitriles is demonstrated. Amidine 1 can be added to cyanoalkyne 2 to give iminopyrimidine isomer 3 with high selectivity. The addition of 2 equiv of NaHMDS completely reverses the selectivity of the reaction, yielding isomer 4 almost exclusively. This method has been used to prepare a variety of substituted 4-iminopyrimidines.     

N-烷基取代烯胺合成方法研究

本文研究了一种通用的N-烷基取代烯胺合成方法。着重探讨了反应物配比、催化剂用量、反应时间等条件对缩合反应的影响。在优化的工艺条件下,能获得纯度较好,收率较高的N-烷基取代烯胺。     

Direct synthesis of highly pure perylene tetracarboxylic monoimide

A series of perylene tetracarboxylic monoimides substituted with cycloalkanes were synthesized through a one-step reaction between cycloalkyl amines and the parent perylene dianhydride. The reaction demonstrates high selectivity for the production of monoimides with no formation of diimides. The high reaction selectivity is primarily due to the insolubility of the monoimides in the reaction medium, which in turn causes rapid precipitation of the products, shifting the reaction equilibrium to the right.     

A double Mannich approach to the synthesis of substituted piperidones—application to the synthesis of substituted E-ring analogues of methyllycaconitine

The double Mannich reaction of acyclic α,γ-substituted β-keto esters and bis(aminol) ethers gives substituted 3,5-substituted-4-piperidones with high levels of diastereoselectivity. These piperdiones can be easily transformed into substituted E-ring analogues of the delphinium alkaloid methyllycacotine.     

The synthesis of 2-ketopiperazine acetic acid esters and amides from ethylenediamines with maleates and maleimides

The reaction of substituted ethylenediamines with various fumarates, maleates, and maleimides to form substituted ketopiperazine acetic acid esters and amides was investigated. This method affords a straightforward, high yield approach to a variety of potential peptidomimetics and can yield surprising results with regard to regio- and stereoselectivity.     

Copper‐Catalyzed Asymmetric Silylation of Propargyl Dichlorides: Access to Enantioenriched Functionalized Allenylsilanes

A copper‐catalyzed silylation of propargyl dichlorides was developed to access chloro‐substituted allenylsilanes under mild reaction conditions. Moreover, enantioenriched chloro‐substituted allenylsilanes can be synthesized in moderate to high yields and good enantioselectivities with this protocol.     

Photopolymerization V. Unsensitized solution photocyclopolymerization of N,N ′-alkylenebismaleimides

The term, “photopolymerization,” is defined as a polymerization process in which every chain-propagating step involves a photo-chemical reaction. This type of polymerization is exemplified by the unsensitized solution photocyclopolymerization of several N,N ′-alkylenebismaleimides, substituted at the double bond. N,N ′-Alkylenebismaleimides substituted with a bromine atom or two methyl groups at their double bond produce high polymeric products upon ultraviolet irradiation in solution. A general reaction scheme for the photopolymerization is proposed. Kinetic measurements show that the solution photopolymerization of substituted bismaleimides is a multistep reaction.     

1,2-sulfanyl group migration as a driving force: new approach to pyrroles by reaction of allenic aldehydes with amines

[reaction: see text] Acid-promoted reaction of sulfanyl group substituted allenic aldehyde with amine affords pyrrole derivatives in high yields. The neighboring group participation of the sulfanyl group is the driving force in this transformation.     

Noble metal ionic sites for catalytic hydrogen combustion: spectroscopic insights

A catalytic hydrogen combustion reaction was carried out over noble metal catalysts substituted in ZrO(2) and TiO(2) in ionic form. The catalysts were synthesized by the solution combustion technique. The compounds showed high activity and CO tolerance for the reaction. The activity of Pd and Pt ion substituted TiO(2) was comparable and was higher than Pd and Pt ion substituted ZrO(2). The mechanisms of the reaction over the two supports were proposed by making use of the X-ray photoelectron spectroscopy and FT infrared spectroscopic observations. The reaction over ZrO(2) supported catalysts was proposed to take place by the utilization of the surface hydroxyl groups while the reaction over TiO(2) supported catalysts was hypothesized to be a hybrid mechanism utilizing surface hydroxyl groups and the lattice oxygen.     

氟取代聚芳醚酮低温合成及其结构研究

通过傅克酰基化反应合成4,4'-二(4-氟苯甲酰基)二苯醚、4,4'-二(五氟苯甲酰基)二苯醚、4,4'-二(4-氟苯甲酰基)二苯硫醚以及4,4'-二(五氟苯甲酰基)二苯醚4种长链双卤单体,并进一步制备了含二氮杂萘酮聚芳醚酮聚合物.通过多氟取代双卤单体在含二氮杂萘酮聚芳醚酮聚合物主链中引入氟原子.多氟取代双卤单体具有多...