2-烷基环戊-2-烯酮的简便合成新方法

2-位取代的环戊-2-烯酮是一类重要的有机合成中间体,它们的合成方法虽然已有不少文献报道,但大都路线较长,原料难得,条件苛刻且收率较低.本文报道一个以环戊二烯为原料,仅两步反应合成2-烷基环戊-2-烯酮的简便新方法. 以聚乙二醇(PEG)作为相转移催化剂,环戊二烯在氢氧化钾作用下与卤代烷在固-液相条件下反应,可方便地得到相应的烷基取代环戊二烯,主要为1-位和2-位烷基取代异构体的混合物.通过该方法制备烷基环戊二烯较之采用钠氨于液氨中反应的通常制备方法更可取.烷基环戊二烯进一步于甲醇中经溴代及酸性水解后,即可得到2-烷基环     

酸性条件下多苯基取代环戊二烯的氧化扩环反应

报道了空气(或氧气)存在的条件下,由高氯酸引发多苯基取代环戊二烯发生新颖的碳-碳键断裂扩环反应,在此反应中,氧原子插入到环戊二烯环中形成相应的六元环吡喃盐类化合物.分别用红外光谱、核磁共振氢谱、碳谱、质谱以及元素分析对所得化合物进行了表征.     

取代苄基五甲氧羰基环戊二烯的合成和晶体结构

五甲氧羰基环戊二烯基钾和取代苄基卤化物反应, 合成了七个新型苄基取代五甲氧羰基环戊二烯。由^1H NMR、IR、元素分析等确认R(苄基)和环戊二烯上碳直接相连, 具有典型的碳碳连结。对产物之一, 1-萘亚甲基五甲氧羰基环戊二烯的X射线衍射测定, 进一步肯定了上述结论。化合物为单斜晶系, 空间群为P2/n, a=0.9731(1), b=1.7403(3), c=1.465(3)nm; β=95.70(1)^°, v=2.4712nm^3, D~c=1.334g/cm^3, 最终的R=0.093, 萘亚甲基环与环戊二烯基环的二面角为68.19^°。     

烯基环戊二烯基ⅣB族金属衍生物的合成和1HNMR谱

6,6-二烷基富烯与烯丙基氯化镁发生环外双键的加成反应,形成1,1-二烷基-3-丁烯基环戊二烯基氯化镁,同苯乙炔基钠则和6-位碳上甲基或亚甲基的c:-H反应,环外双键移位得到乙烯基环戊二烯基钠。这些阴离子与ⅣB族金属氯化物反应合成了一系列新的烯基取代环戊二烯基金属衍生物。     

2-(6′-甲氧羰基己基)环戊-2-烯酮的新合成方法

以环戊二烯为起始原料,制得6-乙氧羰基己基环戊二烯,后者在甲醇溶液中与溴作用后经酸性水解,得到2-(6＇-甲氧羰基己基)环戊-2-烯酮。     

对醇的消去反应规律的商榷

许多资料这样总结醇的消去反应规律:只有和醇羟基所在碳原子相邻的碳上有氢时,醇才能发生消去反应。笔者认为这种说法欠妥,值得商榷。1反应机理醇在酸的作用下,脱水成烯是经过E1反应机制而完成的,如下图所示:醇羟基接受质子,然后以水的形式离去,原羟基所在碳因而带1个正电荷成为碳正离子,碳正离子的邻碳失1个质子,1对电子转移过来中和碳正离子的正电荷从而形成碳碳双键。如果醇羟基接受质子失水后形成的碳正离子的邻碳上无氢而发生重排后形成的碳正离子的邻碳上有氢,则发生重排形成新的碳正离子,接着邻位碳失去质子而成烯。例如:此反应可表…     

艾地苯醌的简便合成

借鉴Hammamura等提出的醌与环戊二烯进行Diels-Alder反应后, 可将醌羰基α-非酸性的烯氢原子转化为羰基α-氢的原理, 将辅酶Q0(5)与环戊二烯的Diels-Alder反应产物(6)在叔丁醇钾-THF体系中, 与以1,10-癸二醇(1)为原料制成的衍生物(4)进行缩合, 再经逆Diels-Alder反应, 得到艾地苯醌, 该方法步骤简洁、条件温和、重现性好、收率较高.     

烯酮及取代烯酮与环戊二烯环加成反应机理的理论研究

利用半经验分子轨道理论AM1方法,研究了烯酮及取代烯酮与环戊二烯环加成反应机理。采用Berny梯度法优化得到各反应的过渡态和中间体,并进行了振动分析确认。计算结果表明,该环加成反应是按照协同的非同步途径进行的,经过一个四元环发生扭曲的过渡态,并有部分电荷从环戊二烯迁移到烯酮或取代烯酮上,前线轨道分析表明反应机理为“2×[1+1]”机理;而氯甲基取代的烯酮与环戊二烯的环加成反应是按照分步途径发生的。计算结果可以很好地说明实验所观察到的立体选择性,并根据烯酮上取代基的电子效应和位阻效应对反应机理的影响进行了分析。     

(CH_3C_5H_4)_3Ln·THF(Ln=Sm,Ho,Tb,Yb)与环戊二烯生成(C_5H_5)_3Ln·THF的新反应

研究了(CH_3C_5H_4)_3Ln·THF (Ln = Sm,Ho,Tb,Yb)与环戊二烯高产率生成 (C_5H_5)_3Ln·THF的新反应。反应产物经过了元素分析、质谱和X射线的表征。产 物(C_5H_5)_3Ln·THF的特征结构参数,如五元碳环的碳原子与中心金属的平均距 离,五元碳环质心与中心金属距离,配位的四氢呋喃氧原子与中心金属距离,由于 “镧系收缩现象”,随着中心原子序数的增加而减小。     

环戊叉基环戊酮的烷基化反应研究

研究了环戊叉基环戊酮与不同类型烷化剂的反应规律；讨论了不同催化剂对烷基化反应的催化性能，发现ＮａＮＨ２和ＮａＨ具有较好的催化作用；讨论了烷基化产物的结构，证实了烷基化反应发生在羰基的α双键碳原子上。     

Oxygen vacancy promoting catalytic dehydration of formic acid on TiO2(110) by in situ scanning tunneling microscopic observation

The catalytic dehydration reaction processes of formic acid on a TiO2(110) surface at 350 K have been studied to visualize reaction intermediates and their dynamic behaviors by scanning tunneling microscopy. Three types of configurations of adsorbed formates on the surface were identified by their shapes and positions in STM images. Successive STM observations revealed transformations among the three configurations, i.e., bridge formate on a 5-fold coordinated Ti4+ row, bridge formate on an oxygen vacancy site with an oxygen atom of formate and on a 5-fold coordinated Ti4+ ion and with the other formate oxygen atom, and a monodentate formate on an oxygen vacancy site with an oxygen atom of formate. The decomposition of the monodentate formate to carbon monoxide and hydroxyl was also imaged, which is a rate-determining step in the catalytic dehydration of formic acid. Combined with first-principle DFT calculations, the overall reaction processes of the catalytic dehydration of formic acid on the surface have been elucidated. Oxygen vacancies on the surface that can be produced by dehydration of two hydroxyls in situ under the catalytic reaction conditions are essential for the reaction.     

焦脱镁叶绿酸-a甲酯的E-环格氏反应及其脱氧衍生物的合成

以焦脱镁叶绿酸-a甲酯及其3-甲酰甲基为起始原料,通过与直链烷基溴化镁或者环烷基溴化镁进行格氏反应,将131-位羰基转化为烷羟基,经脱水在E-环形成环外碳碳双键,完成单(双)烷亚甲基取代的131-脱氧焦脱镁叶绿酸衍生物的合成,并且讨论了格氏反应的立体化学.所合成的新化合物均经UV,IR,1H NMR及元素分析证明其结构.     

4-Azidotetronic Acids: A New Class of Azido Derivatives

4-Azidotetronic derivatives bearing different substituent groups on the carbon atom in position 3 were easily obtained by reaction of the corresponding 4-bromotetronic compounds with sodium azide in methanol at room temperature.     

One-pot synthesis of N-substituted pantolactams from pantolactone

Rac-N-substituted pantolactams (5) are readily obtained in medium to good yields by reaction of rac-pantolactone (1) with primary amines under acid catalysis, whether at 250°C in a pressure reactor or under microwave irradiation. It appears that the amine can react with pantolactone at the carbonyl carbon atom to give a hydroxyamide (3) in a reversible way and at the methylene carbon atom to give a γ-amino acid (4). The last one on dehydration would give the corresponding pantolactam (5).     

Mebbrane extraction of organic compounds

New lipophilic α-aminophosphonates containing cyclic or acyclic alkyl substiuents at the carbon atom in the α position were synthesized by the Kabachnik-Fields reaction. Studies of the obtained compounds as carriers for transport of glycolic acid through polymermembrane depends on the lipophilicity and the presence of substituents at the α- C atom of aminophosphonate. The structures of a number of α-aminophosphonate-glycolic acid complexes were calculated by the semiempirical PM3 method.     

Intramolecular construction of trifluoromethyl group by the palladium-catalyzed reaction of 2,3,3-trifluoroallylic carbonates with O-nucleophiles

The synthesis of the trifluoromethyl group containing enol ethers by the palladium-catalyzed intermolecular reaction of 2,3,3-trifluoroallylic carbonates with oxygen nucleophiles was accomplished. The reaction proceeds through the intermolecular attack of oxygen nucleophiles on the C-2 carbon atom of the allylic unit, and the intramolecular fluorine atom shift from the C-2 position to the C-3 position. The reactions with several types of alcohols and phenols proceeded smoothly, and afforded the corresponding trifluoromethyl group containing enol ethers in good to high yields.     

Influence of the structures of α-halo ketones and thioamides on the Hantzsch synthesis of thiazoles and thiazolo[5,4-b]indoles. A new approach to 4-acetyl-2-methyl-4H-thiazolo[5,4-b]indole

In reactions with some α-halo ketones (3-bromo-1,1,1-trifluoropropan-2-one, 1-acetyl-2-bromoindolin-3-one, and α-bromoacetophenone), thioacetamide and a series of thioamides of aromatic and heteroaromatic acids are transformed into 4-hydroxy-Δ²-thiazolines rather than into thiazoles (the expected Hantzsch reaction products). To the contrary, thiazoles are produced in the reactions of the same α-halo ketones with thioamides of phenylacetic, diphenylacetic, 3-indolylacetic, or cyanoacetic acids. The abnormal course of the Hantzsch reaction in the former case results from the fact that 4-hydroxy-Δ²-thiazolines, which are intermediates in the thiazole synthesis, undergo virtually no dehydration under the Hantzsch reaction conditions. The ease of dehydration of hydroxythiazolines under the conditions of the thiazole synthesis and the possibility of the spontaneous thiazole synthesis depend on the nature of the substituent at position 2 and, consequently, on the structure of the starting thioamide. The Me, Ar, and Het substituents impede dehydration, whereas substituents containing the α-methylene (methine) unit at the C(2) atom of the thiazoline moiety substantially facilitate this reaction. The conditions for the dehydration of 4-acetyl-2-methyl-8b-hydroxy-3a,8b-dihydro-4H-thiazolo[5,4-b]indole under basic catalysis were found, and a new procedure was developed for the preparation of thiazoles and 2-R-thiazolo[5,4-b]indoles, whose synthesis presents difficulties or is impossible under standard conditions.     

Prediction of radical reaction site(s) of polycyclic aromatic hydrocarbons by atomic charge distribution calculation using the DFT method

The atomic charge distributions on each atom of the PAHs were obtained using the CHelpG and MK methods with the optimized structural parameters determined by DFT calculation at the level of BLYP/6-311++G(d,p). By comparing the experimentally obtained oxidation position(s) and the calculated atomic charges on carbon atoms of PAHs, we found that the oxidation reaction mainly occurred at the carbon(s) having the higher atomic charges.     

反式-3-苯基-12-取代环十二酮的合成及晶体结构

以环十二酮为原料,经2-碘酰基苯甲酸(IBX)氧化制备2-环十二烯酮,在醋酸钯和三苯基磷催化下,2-环十二烯酮与苯硼酸反应制得3-苯基环十二酮.经3-苯基环十二酮与不同试剂发生区域选择性反应制备了一系列新的3-苯基-12-取代环十二酮衍生物,采用核磁共振波谱(NMR)和液相色谱-高分辨质谱(HRMS)表征了其结构.在溶液中结晶,获得了4个代表性化合物的单晶并进行X射线衍射分析,结果表明,3-苯基-12-取代环十二酮晶体中的十二元环仍采取[3333]-2-酮构象,2个取代基为反式构型,取代基存在2种情形:2个取代基在同一条边上,苯基位于与羰基间隔1个亚甲基的β-角碳反向位,而另1个取代基位于与羰基另一侧相邻的α-角碳顺向位;或2个取代基在2条边上,苯基位于与羰基间隔1个亚甲基另一条边的β-边碳外向位,而另1个取代基位于与羰基另一侧相邻并在同一条边的α-边碳外向位,量子力学计算结果与晶体衍射分析结果一致.     

The mutual influence of the imine substituents of terephthal-bis-imines concerning their reactivity towards Fe2(CO)9

The reaction of terephthal-bis-imines with Fe₂(CO)₉ proceeds via a C---H activation reaction in the ortho position with respect to one of the imine functions. The corresponding hydrogen atom is shifted towards the former imine carbon atom producing a methylene group instead. The dinuclear iron complexes formed by this reaction sequence and showing no coordination of the second imine group were isolated from reactions of bis-imines with both phenyl and cyclohexyl substituents at the imine nitrogen atoms. In addition, we observed three different reaction pathways of the second imine substituent of the starting material which is obviously thus influenced by the fact that the first one is coordinating an Fe₂(CO)₆ moiety. If the organic substituent at the imine nitrogen atoms is a phenyl group the formation of a trinuclear complex is achieved in which an additional Fe(CO)₃ group is coordinating the CN double bond and one of the carbon---carbon bonds of the central phenyl ring in an η⁴-fashion. The same reaction leads to the isolation of a tetranuclear iron---carbonyl compound in which both imine substituents were transformed via the pathway described above, each building up dinuclear subunits. In contrast to this the reaction of a bis-imine with cyclohexyl groups at the imine nitrogen and thus an enhanced nucleophilicity leads to the formation of a tetranuclear complex in which only one imine group reacts under C---H activation with subsequent hydrogen migration towards the former imine carbon atom. The second imine substituent also shows a C---H activation reaction in the ortho position with respect to the imine group but the corresponding hydrogen atom is transferred to one of the aromatic carbon atom of the central phenyl ring of the ligand. The C=N double bond remains unreacted and only coordinates the second Fe₂(CO)₆ moiety via the nitrogen lone pair.