Effect of substituent structure on pyrimidine electrophilic substitution

In an investigation into the electrophilic nitrosation reactions of a series of 4,6-disubstituted pyrimidine derivatives, a subtle interplay between the electronic nature of the C-4 and C-6 substituents and reactivity was found where these were chloro-, mono- or disubstituted amino groups. Effects such as the presence of an aryl group or two alkyl groups on the amino moiety impede the progress of the reaction despite the presence of a second activating group.     

Copper-catalyzed C-N coupling reactions of aryl halides with α-amino acids under focused microwave irradiation

We have developed an efficient method for the preparation of enantiopure N-aryl-α-amino acids via copper-catalyzed N-arylation of α-amino acids and aryl halides under microwave irradiation. This protocol only needs less than 30 min to obtain the products, which are far superior to those obtained under conventional heating.     

Unexpected stereoselective sodium acetate catalyzed multicomponent cyclization of aryl aldehydes, malononitrile and acetone into cis-4-dicyanomethylene-2,6-diarylcyclohexane-1,1-dicarbonitriles

A new type of multicomponent reaction is described in which five organic molecules form a cyclohexane ring. Aryl aldehydes, malononitrile and acetone in the presence of a catalytic amount of sodium acetate are stereoselectively cyclized into cis-4-dicyanomethylene-2,6-diarylcyclohexane-1,1-dicarbonitriles in 30-60% yields.     

Pyridine‐4‐thiol and Amphoteric Analogs: Novel Protection of Aryl Bromides in Strong Alkali

The use of pyridine‐4‐thiol (PT) to preserve certain aryl bromides in strong alkali is reported (Scheme 1). The presence of this additive or of some of its amphoteric analogs such as 3‐hydroxypyridin‐4(1H)‐ones suppresses the replacement of the Br‐substituent by hydroxide and alkoxide ions. A mechanistic interpretation of the effect is proposed.     

Pd-Cu catalyzed heterocyclization during Sonogashira coupling: synthesis of 2-benzylimidazo[1,2-a]pyridine

The reaction of 2-amino-1-(2-propynyl)pyridinium bromide with various iodobenzenes, catalyzed by Pd-Cu, leads to the formation of 2-benzylimidazo[1,2-a]pyridines.     

Synthesis of Arylnaphthoquinones and Their Reactions with o‐Substituted Primary Aromatic Amines

Cycloaddition reaction of 2‐aryl‐1,4‐benzoquinones 1a‐d with a number of different dienes, namely 2,3‐dimethylbutadiene; 1,4‐diphenylbutadiene and anthracene yield 2‐aryl‐6,7‐dimethyl‐1,4‐ naphthoquinones 3a,b ; 2,5,8‐triphenyl‐1,4‐naphthoquinone 4 and 2‐aryl‐1,4,9,10‐tetrahydro‐9,10‐o‐benzoanthracene‐1,4‐dione 5 , respectively were investigated. In addition, the cycloaddition reaction of 2‐aryl‐1,4‐benzoquinones 1d,e with 2,3‐dimethylbutadiene was also investigated to yield 2‐aryl‐5,8‐dihydro‐6,7‐dimethyl‐1,4‐naphthohydroquinones 2a,b . Cyclocondensation reactions of Diels‐Alder adducts 2b, 3b, 5a with ethylenediamine, o‐substituted primary aromatic amines gave quinoxaline, phenazine, phenoxazine and phenothiazine ocyclic derivatives 6–14.     

取代基电子效应对芳基甲烷氧化缩合反应及产物的影响

研究了数种芳基甲烷在有机溶剂中碱催化下的氧化缩合反应,并对反应产物进行了表征,结果表明,芳基甲烷中取代基的吸电子效应影响其氧化缩合反应活性及产物结构特征,取代基吸电性越强,吸电基越多,氧化缩合越易发生,     

Copper-mediated O-arylation of lactols with aryl boronic acids

A novel and efficient method to access phenolic glycosides has been established by using copper-mediated coupling reaction of aryl boronic acids with hemiacetals. The reaction enjoyed a wide range of substrate scope, and many phenolic glycosides can be synthesized in good yields.     

Highly efficient CuOx/OMS-2 catalyst for synthesis of phenoxathiin derivatives via intramolecular arylations of phenols with aryl halides

Phenoxathiin and its derivatives have attracted a great deal of interest due to their unique chemical and physical properties and their applications in fluorescent materials, antifungal activities and selective inhibitors. In the presence of copper supported on manganese oxide-based octahedral molecular sieves OMS-2 (CuO_x/OMS-2), the heterogeneously catalytic synthesis of phenoxathiinan derivatives via intramolecular arylations of phenols with aryl bromide or aryl chloride has been achieved. TEM and XRD have confirmed the CuO_x/OMS-2 catalyst has been successfully reused 8 times without a significant decrease in the yield, with simple filtration and washing as a means of separation.     

PVP-蒙脱土双负载Pd-Sn催化剂催化芳香卤化物水相脱卤

负载型双金属催化剂 ,由于双金属的协同作用 ,使催化活性明显提高 .因而负载型双金属催化剂用于催化有机反应 ,已成为人们研究的热点 .高聚物负载双金属催化剂催化有机卤化物脱卤已有报道[1～ 3] ,但脱卤反应大多在有机相中进行 ,若在水相中 ,催化剂则失去活性[2 ] ,且不易回收和重复使用 .然而有毒的卤化物常存在于化工、印染等工业排放的废水中 ,这些废水流入江、河、湖、海或渗漏在地下 ,造成对水体的严重污染 .为消除废水中有机卤化物对环境的污染 ,我们将 PVP(聚乙烯吡咯烷酮 )负载双金属后再负载到无机载体蒙脱土( Mont K1 0 )上 ,…