Preparation and reaction of uracil substituted cyclen and cyclam: formation of tricyclic guanidinium and dihydroimidazolium salts

Di-uracil substituted cyclen derivatives were prepared by the reaction of cyclen with 6-chloro-1-methyluracil or 6-chloro-1,3-dimethyluracil. The reaction of cyclam with 6-chloro-1,3-dimethyluracil gave a similar di-uracil substituted cyclam. The 1,7-di-uracil substituted cyclen was converted to the tricyclic guanidinium salt and acylurea upon heating in DMSO in the presence of weak acid. The 1,8-di-uracil substituted cyclam gave a tricyclic dihydroimidazolium salt under the same conditions. These reactions can be explained by an intramolecular uracil ring-breaking reaction mechanism.     

Versatile access to benzhydryl-phenylureas through an unexpected rearrangement during microwave-enhanced synthesis of hydantoins

[reaction: see text] A new access to benzhydryl-phenylureas is described. These new interesting urea derivatives were obtained by reaction of substituted benzils with substituted phenylureas under microwave irradiation. Phenylthiourea, when reacted with benzil, gave 3-phenyl-thiohydantoin. Moreover, benzylurea, as phenethylurea, gave the corresponding 3-substituted hydantoin derivatives, demonstrating that only phenylurea derivatives can result in benzhydryl-phenylureas under the applied conditions. This new reaction proved to be an easy access to substituted 1-benzhydryl-3-phenyl-ureas.     

Generation of ketone dilithio α,β-dianions and their reactions with electrophiles

Ketone dilithio α,β- and α,β′-dianions can be generated by a tin-lithium exchange reaction of the lithium enolate of β-tributyltin substituted ketones. A chelation-aided approach, which employs β-dichlorobutyltin substituted ketones and n-BuLi, is also useful for the generation of ketone α,β-dianions having the Z-geometry at the alkene. The generated dianions can be transformed into substituted ketones by reaction with various carbon electrophiles.     

Impregnated copper on magnetite as catalyst for the O-arylation of phenols with aryl halides简

Nanoparticle Fe304 encapsulated CuO, as a heterogeneous catalyst, is a facile system for the synthesis of diaryl ethers by the cross-coupling reaction of various substituted aryl halides with various substituted phenols, which avoids using any type of expensive ligand and can be recovered from the reaction mixture by using a simple magnet. Moreover, this catalyst can be reused three times with high catalytic activity.     

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.     

非对称氮杂环丙烷的亲核开环反应及其区域选择性

本文系统地总结了各类亲核试剂对非对称氮杂环丙烷(吖丙啶)的亲核开环反应及开环的区域选择性.氮杂环丙烷亲核开环的区域选择性是一种空间效应和电子效应平衡的结果,非芳基和非烯基取代的氮杂环丙烷的亲核开环通常发生在氮杂环丙烷取代少的碳原子上,空间效应起主导作用;而芳基和烯基取代的氮杂环丙烷的亲核开环通常发生在氮杂环丙烷芳甲位和烯丙位的碳原子上,电子效应起主导作用,烯基取代的氮杂环丙烷的亲核开环还可以发生在烯基的β-碳原子上;分子内的亲核开环反应主要受成环时环大小的控制,成环时的倾向是五元环>六元环>七元环.对于亲核试剂,一般的亲核试剂也同时受电子效应和空间效应的影响; 而亲核性强的亲核试剂通常只受空间效应的影响.容易生成稳定自由基的亲核试剂容易发生单电子转移机理的开环反应,生成相当于亲核试剂进攻氮杂环丙烷中取代多的碳原子得到的开环产物.     

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.     

Regio‐ and Stereoselective Modification of Chiral α‐Amino Ketones by Pd‐Catalyzed Allylic Alkylation

Chiral α‐amino ketones are excellent nucleophiles for stereoselective palladium‐catalyzed allylic alkylations. Both chiral as well as achiral allylic substrates can be applied, while the stereochemical outcome of the reaction is controlled by the chiral ketone enolate. The substituted amino ketones formed can be reduced stereoselectively, and up to five consecutive stereogenic centers can be obtained. This approach can be used for the synthesis of highly substituted piperidine derivatives.     

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.     

Formamidinoylisothiocyanate—III : Addition nucleophiler partner an formamidinoylisothiocyanate

Formamidinoylisothiocyanates combine with amines to give substituted guanylthioureas. By addition of 2-aminothiazole azacondensed thiazolo-s-triazines are obtained. Treatment of the guanylthioureas with bromine yields 1,2,4-thiodiazolines.The reaction between N³-phenylbenzamidrazone and formamidinoylisothiocyanates yields thiosemicarbazides, which are substituted with imidoyl- and amidino-groups. CH-acid thioamid can be synthesized by the reaction of cyanoaceticester and formamidinoylisothiocyanates.     

Tandem Oxidation Process Using Ceric Ammonium Nitrate: Three-Component Synthesis of Trisubstituted Imidazoles Under Aerobic Oxidation Conditions

By combining a ceric ammonium nitrate (CAN)–catalyzed aerobic oxidation of α-hydroxy ketones with a subsequent three-component condensation reaction using aldehydes and ammonium acetate, highly substituted imidazole derivatives can be assembled. This reaction is an important approach for the synthesis of highly substituted imidazole derivatives and was carried out in good to excellent yields in ethanol as an environmentally benign solvent.     

Polylithiumorganic compounds. Part 29: C,C Bond cleavage of phenyl substituted and strained carbocycles using lithium metal

The reaction of phenyl substituted cyclopropanes phenylcyclopropane and 1,1-diphenylcyclopropane, phenyl substituted bicyclobutanes 1-phenylbicyclobutane, 1-methyl-3-phenylbicyclobutane, 1-methyl-2,2-diphenylbicyclobutane, as well as phenyl substituted spiropentanes phenylspiropentane and 1,1-diphenylspiropentane with lithium metal or lithium di-t-butylbiphenyl (LiDBB) was investigated. Under suitable reaction conditions and choice of solvent in all cases cleavage of the single bond next to the activating phenyl group was observed. The dilithiumorganic compounds thus obtained are sufficiently stable and can be trapped with electrophiles. Lithium hydride elimination is observed as follow-up reaction only in a few cases. The corresponding anions of the strained ring systems 1-lithio-2,2-diphenylcyclopropane, 1-lithio-3-phenylbicyclobutane, 1-lithio-3-methyl-2,2-diphenylbicyclobutane, and 1-lithio-4-phenylspiropentane, which can be obtained by lithium bromine exchange or by metalation of the unsubstituted carbocycle, do not show any cleavage upon reaction with lithium metal.     

Synthesis of new non‐symmetrical substituted 7,7′‐bisindolizines by the direct reaction of 4,4′‐bipyridinium‐ylides with dimethyl acetylenedicarboxylate

We report here on the synthesis of some novel non‐symmetrical substituted bisindolizines by 3+2 dipolar cycloaddition reaction. New compounds were prepared by the direct reaction of isolated non‐symmetrical substituted 4,4′‐bipyridinium bisylides with dimethyl acetylenedicarboxy late (DMAD). The obtained compounds can be used as precursors of fluorescent markers in fluorometric analysis.     

硫酸盐水合物催化下的酯化反应 II: 催化线性自由能方程

A new relationship based on the Hammett equation is derived for the esterification reaction of substituted carboxylic acid in the presence of hydrated sulphate salts and is called a catalyzing linear free energy equation. The equation can be expressed as log(KR(M)/K0Mn))=\s\*\T\^M + Ym where KR(M) is the rate constant of the esterification reaction of substituted acetic acid catalyzed by hydrated sulphate salts of M matal, K0(Mn) is the rate constant of that of acetic acid catalyzed by MnSO4.H2O, Ym is active index of catalyst. For reactions catalyzed by certain catalysts the rate constant of substituted acetic acid can be estimated from the equation.     

Nickel‐Catalyzed Arylboration of Alkenylarenes: Synthesis of Boron‐Substituted Quaternary Carbons and Regiodivergent Reactions

A method for the construction of boron‐substituted quaternary carbons or diarylquaternary carbons by arylboration of highly substituted alkenylarenes is presented. A wide range of alkenes and arylbromides can participate in this reaction thus allowing for a diverse assortment of products to be prepared. In addition, a solvent dependent regiodivergent arylboration of 1,2‐disubstituted alkenylarenes is presented, thus greatly increasing the scope of products that can be accessed.     

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.     

钯催化四氟硼酸芳香重氮盐的乙氧基羰基化反应

取代苯甲酸乙酯;制备;钯催化四氟硼酸芳香重氮盐的乙氧基羰基化反应     

Dynamic exchange of heterocyclic subunits during halogen substitution in chloroheptamethinecyanine dyes by benzoazolium salts

The chlorine atom present in the exocyclic conjugated bridge incorporated in the polymethine chain of heptamethinecyanine dyes can be easily replaced by a substituted 2-methylbenzoazolium salt. This reaction is promoted by residual water present in the reaction medium. This strategy was applied to the synthesis of a heptamethinecyanine dye possessing a vinyl group in the substituting heterocycle. Surprisingly, the expected monovinyl substituted dye was obtained along with di- and trisubstituted vinyl dyes. Such mixture can be, in principle, incorporated into an organic polymer monolith and used for affinity chromatography. This substitution reaction was investigated varying the nature of the benzoazole moiety of the chloroheptamethinecyanine dye and the substituting 2-methylbenzoazolium salt. A mechanism rationalizing the substitution pattern observed is proposed.     

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。     

Platinum‐Catalyzed Multi‐Step Reaction of Propargyl Alcohols with N‐Heteroaromatics

N‐Methyl indole reacts with but‐2‐yn‐1‐ol in the presence of PtCl₂ in MeOH giving indole derivatives having a substituted 3‐oxobutyl group at the 3‐position in good yield. Under the reaction conditions, various substituted indoles and substituted propargyl alcohols are successfully involved in the reaction giving the corresponding addition products in good to moderate yields. The catalytic reaction can be further extended to N‐phenyl pyrrole. In the present multi‐step reaction, PtCl₂ likely plays dual roles: as the catalyst for the rearrangement of propargyl alcohols to the corresponding alkenyl ketones and as the catalyst for the addition of indoles to the alkenyl ketones. Experimental evidence is provided to support the proposed mechanism.