聚苯乙烯二醋酸碘苯的合成及其在烯烃叠氮-芳硒化反应中的应用

近年来 ,高碘化合物显示出多样化的反应性能 ,广泛用于有机合成 .其中以二醋酸碘苯的应用最为广泛 [1] .Tingolio等[2 ] 报道烯烃与二醋酸碘苯、叠氮化钠及二芳基二硒化合物进行叠氮 -芳硒化反应 ,具有反应条件温和、区域选择性好等优点 ,不足之处在于副产物碘代苯不易与产物分离 ,亦不符合原子经济性原则 .合成聚合物负载的有机试剂发展极为迅速 ,其主要优点是过量的试剂 ,在反应完成后 ,通过简单过滤即可与产物分离 ,而且聚合物试剂可被再生 ,重复使用 ,充分体现了绿色化学的特征 [3 ,4 ] .为此 ,本文首先合成聚苯乙烯负载的二醋酸碘苯试…     

α-溴代二硫缩烯酮的制备及其反应

α-羰基二硫缩烯酮 ( 1 )是一类重要的有机合成中间体 ,作为 1 ,3-亲核体用于酯环、苯系芳烃及芳杂环化合物的合成[1～ 4 ] .Hosomi等 [5～ 7] 用有机铜试剂或二碘化钐和 α-羰基与二甲硫缩烯酮反应 ,将与硫相连的缩烯酮碳原子转化为亲核中心 .用不同的烷硫基作为调控基团将该类中间体用于二萜 pseu-dopterosins的合成 [8～ 10 ] ,并作为替代 Peterson法合成 1 ,1 -二烷硫基 - 1 ,3-丁二烯或 1 ,1 -二烷硫基 - 1 ,3,5 -己三烯 [11,12 ] ,从不同的角度对 α-羰基二硫缩烯酮在合成上的应用进行了新的探索 .Junjappa等 [13,14 ] 曾用 NBS和 …     

一种以硒脲为原料高效合成5-氨基四氮唑类化合物的新方法

以1,3-二取代硒脲为原料,在离子液体负载的二醋酸碘苯和叠氮化钠存在下经电环化反应合成了系列5-氨基四氮唑类化合物,反应时间短、选择性好、收率高.该反应使用了绿色试剂离子液体负载的二醋酸碘苯[dibmim]~+[PF_6]~-,对环境无污染,且可循环使用,符合绿色化学的要求.     

醋酸碘苯介导的α-重氮羰基化合物的去重氮双氧合反应

报道了一类新颖的醋酸碘苯介导的α-重氮羰基化合物的去重氮双氧合反应.该反应利用醋酸碘苯与N-羟基邻苯二甲酰亚胺(或N-羟基丁二甲酰亚胺)反应能产生氧中心自由基的特性实现了氧中心自由基诱导的α-重氮羰基化合物的双氧合反应,合成了一系列α,α-双氧代芳酮和α,α-双氧代羧酸酯衍生物,产率中等到良好.基于实验结果及文献报道,提出了可能的反应机理,其涉及氧中心自由基加成、C-N键的均裂和自由基交叉偶联等.此外,该反应具有无需金属催化剂、条件温和、操作简便等优点.     

简便的β-二羰基化合物直接不对称α-苯乙炔基化反应

通过苯乙炔和羟基(+)-10-樟脑磺酰氧基碘苯在氯仿溶剂中反应, 合成出一个新的手性炔基芳基碘盐[苯基(苯乙炔基)(10)-樟脑磺酸碘盐]. 该手性碘盐与β-二羰基化合物的烯醇式负离子在温和条件下易于反应, 产物具有中等e.e.值, 为β-二羰基化合物在α位不对称引进苯乙炔基提供了一个简单方便的方法.     

2,2,5,5-四甲基-4-羟次甲基四氢呋喃酮-3与某些氨基脲的反应Ⅱ.三氮七元环化合物的合成

我们曾报告2,2,5,5-四甲基-4-羟次甲基四氢呋喃酮-3(Ⅰ)与芳烃邻二胺作用,生成含二个氮原子的七元杂环化合物^[1].Losse等^[2]利用某些1,3-二羰基化合物与氨基硫脲或2-烃基取代氨基硫脲作用,得到三氮七元杂环(1,2,4-triazepine)类化合物.但到目前为止,对这类化合物还研究得极少.羟次甲基四氢呋喃酮(Ⅰ)中的羟基易与胺进行缩合,生成相应的Sehiff碱.我们用化合物(Ⅰ)与氨基脲在室温下反应,生成相应的缩氨脲(Ⅱ).(Ⅱ)在酸性介质中加热时,即环化为相应的三氮七元杂环化合物(Ⅲ).     

以二氧化碳为C1合成子的羧基化/环化反应研究进展

二氧化碳具有价廉易得、储量丰富及无毒等优点,在有机合成反应中是一种理想的C1合成子.近年来,以二氧化碳作为羰基/羧基源,通过环化反应,特别是多组分环化反应构建含羰基杂环化合物,已经取得了重要的研究进展.主要总结了利用含氮、氧亲核原子的试剂与常压条件下二氧化碳的环化反应构建苯并噁嗪、环碳酸酯、内酰胺、2,4-二噁唑啉酮等含羰基杂环结构的工作;其次,也总结了利用含碳亲核原子的试剂与二氧化碳羧基化反应的相关工作.     

双〔取代苯乙酮基β-二酮基〕合铜(Ⅱ)的合成及表征

用取代苯乙酮基β-二酮与醋酸铜作用合成了双[取代苯乙酮基β-二酮基]合铜(Ⅱ)配合物1—3。后者与氨基脲作用,得到相应的缩氨脲4—6。     

α-羰基二硫缩烯酮类化合物在杂环合成中的应用进展

α-羰基二硫缩烯酮是一类重要的有机合成中间体,其官能团的多样性决定了反应的多样性.基于α-羰基二硫缩烯酮的主要反应有与亲核体的共轭加成、与金属有机试剂的选择性加成、环合、还原、缩合等反应以及作为代硫醇试剂的应用等.本文介绍了此类化合物的结构特征及合成方法,并着重按所合成杂环化合物的类型,分别对其在含氮、含氧、含硫及含多...     

2-(1,3-亚丙二硫)亚甲基-3-羰基丁酸作为硫醇替代试剂在缩硫醛/酮化反应中的应用

探讨了以2-(1,3-亚丙二硫)亚甲基-3-羰基丁酸作为硫醇替代试剂,乙醇作溶剂的缩硫醛/酮化反应.实验结果表明,该硫醇替代试剂能与各类醛、酮化合物快速、顺利地进行缩硫醛/酮化反应,以较高的产率生成相应的1,3-二噻烷类化合物.同时,该缩硫醛/酮化反应对不同的醛、酮化合物具有较高的化学选择性.     

玉米秸秆纤维素在亚/超临界乙醇中液化生成酮类化合物的机理探讨

利用间歇式高压反应釜,在反应温度320℃、反应时间60 min条件下,研究乙醇用量对玉米秸秆纤维素液化生成酮类化合物的作用。当乙醇添加量为0时,酮类化合物的产率仅为1.25%。随着乙醇用量由0增加到160 mL,生物油产率不断的升高,酮类化合物产率增加至18.38%,乙醇促进了纤维素液化生成酮类化合物。利用GC/MS和FT-IR对生物油进行了定性分析,结果表明,在亚/超临界乙醇中,酮类化合物主要通过三条路径形成,纤维素脱水形成了含-C=O的活性纤维素,活性纤维素按逆Diels-Alder机理进行开环、脱水、异构化形成了4-羟基-4-甲基-2-戊酮等脂肪族酮类化合物;在乙醇自由基作用下,活性纤维素中C-O-C、C-C等键断裂、开环,形成环戊烯酮等脂环族酮类化合物,环戊烯酮与多种中间产物发生缩合、酯化形成2-甲酸基-1-苯基乙酮等芳香族酮类化合物;在高浓度乙醇自由基作用下,芳香族酮类化合物进一步发生裂解形成酸类、酮类等化合物。根据对酮类化合物生成机理的分析,建立了纤维素在亚/超临界乙醇中液化生成酮类化合物的反应网络。     

Two classes of enzymes of opposite stereochemistry in an organism: one for fluorinated and another for nonfluorinated substrates

Reduction of methyl ketones by dried cells of Geotrichum candidum (APG4) afforded (S)-alcohols in excellent enantiomeric excess (ee), whereas the reduction of trifluoromethyl ketones gave the corresponding alcohols of the opposite configuration also in excellent ee. The replacement of the methyl moiety with a trifluoromethyl group alters both the bulkiness and the electronic properties, the effect of which on the stereoselectivity was examined. No inversion in stereochemistry was observed in the reduction of hindered ketones such as isopropyl ketone, while the stereoselectivity was inverted in the reduction of ketones with electron-withdrawing atoms such as chlorine. The mechanism for the inversion in stereochemistry was investigated by enzymatic studies. Several enzymes with different stereoselectivities were isolated; one of them catalyzed the reduction of methyl ketones, and another with the opposite stereoselectivity catalyzed the reduction of trifluoromethyl ketones. Furthermore, both APG4 and the isolated enzyme were applied to the reduction of fluorinated ketones on a preparative scale, which resulted in the synthesis of chiral fluorinated alcohols with excellent ee.     

叔丁醇钾催化酮硅氢加成反应

介绍了一种用叔丁醇钾催化酮硅氢加成,水解合成醇的方法.以甲苯为溶剂,室温下,叔丁醇钾可高效催化酮与三乙氧基硅烷的硅氢加成反应,酮转化率在90%以上.该方法具有操作简捷、方法简单等优点.     

Studies on K2CO3-catalyzed 1,4-addition of 1,2-allenic ketones with diethyl malonate: controlled selective synthesis of beta,gamma-unsaturated enones and alpha-pyrones

The K2CO3 (10 mol %)-catalyzed 1,4-addition reaction of diethyl malonate with various substituted 1,2-allenic ketones leading to polyfunctionalized beta,gamma-unsaturated enones 3 or 4 was studied. With 3-unsubstituted 1-substituted-1,2-allenyl ketones, the highly selective formation of beta,gamma-unsaturated enones 4 was observed; with 1,2-allenyl ketones bearing one or two 3-substituents in the allenyl group, only beta,gamma-unsaturated enones 3 with an unmigrated carbon-carbon double bond were produced; with 3-monosubstituted-1,2-allenyl ketones Z-beta,gamma-unsaturated enones 3 were formed with excellent stereoselectivity (E:Z > 96:4); with propadienyl ketones, mixtures of beta,gamma-unsaturated enones 3 and 4 were formed. alpha-Pyrone derivatives were synthesized via the K(2)CO(3)-catalyzed or -promoted reaction of 1,2-allenic ketones with diethyl malonate via a sequential Michael addition-carbon-carbon double bond migration-lactonization process.     

Enantioselective synthesis of 2,2-disubstituted terminal epoxides via catalytic asymmetric Corey-Chaykovsky epoxidation of ketones

Catalytic asymmetric Corey-Chaykovsky epoxidation of various ketones with dimethyloxosulfonium methylide using a heterobimetallic La-Li(3)-BINOL complex (LLB) is described. The reaction proceeded smoothly at room temperature in the presence of achiral phosphine oxide additives, and 2,2-disubstituted terminal epoxides were obtained in high enantioselectivity (97%-91% ee) and yield ( > 99%-88%) from a broad range of methyl ketones with 1-5 mol% catalyst loading. Enantioselectivity was strongly dependent on the steric hindrance, and other ketones, such as ethyl ketones and propyl ketones resulted in slightly lower enantioselectivity (88%-67% ee).     

Synthesis of enantiopure homoallylic ethers by reagent controlled facial selective allylation of chiral ketones

The stereoselective allylation of chiral methyl ketones to give tertiary homoallylic ethers, which can easily be transformed into homoallylic alcohols, is described. Reaction of the enantiopure ketones 8a-d and the racemic ketones 26a-d with the norpseudoephedrine derivative 2 or ent-2 and allylsilane in the presence of a catalytic amount of trifluoromethanesulfonic acid, led to a series of homoallylic ethers with good to excellent diastereoselectivity (85:15 to > 97:3). The allylation is reagent controlled and nearly independent from the stereogenic centers in the substrates. A partial kinetic resolution was observed using the racemic ketones 26a-d. In the reaction of the chiral ketones 8a-d with the achiral reagents ethoxytrimethylsilane and allylsilane only a low diastereoselectivity was observed.     

Photopolymerization of methyl methacrylate sensitized by aliphatic ketones

The polymerization of methyl methacrylate photosensitized by several alkyl ketones has been investigated. It was found that alkyl ketones can induce the free radical polymerization of the monomer with an efficiency that increases when the triplet lifetime decreases. For ketones of similar triplet lifetime those decomposing predominantly by a type I photocleavage show greater initiation efficiencies than those that react by a type II mechanism. The results obtained show that quenching of the excited ketones by the monomer does not induce polymerization. For ketones bearing γ-hydrogens the initiation is due to the 1,4-biradical produced by intramolecular hydrogen abstraction.     

Reduction of Aromatic Aldehydes,Ketones with Acyloxy Substituent at the Ortho-position by NaBH4 in the Presence of Waters

n unusual reduction of some aromatic aldehydes, ketones by sodium borohydride was discovered. In a THF/H₂O or DMSO/H₂O solvent system the aromatic aldehydes, ketones with acyloxy substituent on the ortho-position to the carbonyl group can be reduced to the corresponding alkyl phenols. This unusual reduction is applicable also to the corresponding alcohols of all the above aldehydes, ketones. A putative mechanism was suggested. In addition to the above aldehydes, ketones, benzyl alcohols, certain 4-acyloxybenzyl esters(probably also the 2-substituted analogues) such as 4-benzoyloxybenzyl benzoate was also found to be reduced to methylphenol by this unusual reduction.     

Reaction of Crossed Diperoxidation Between Cyclic Ketones and Alkyl Ketones

IntroductionThe thermal and photochemical decompositionof the diperoxides of cyclic ketones has been foundto provide a general method for the facile synthesisof macrocyclic compounds[1,2 ] .In addition,the useof diperoxides as initiators in polymerization hasbeen studied[3] .Forthose reasons,a better methodfor the synthesis of the requisite diperoxides isrequired.There are two different methods for thepreparation of the diperoxides. Griesbaum[4 ]obtained cyclopentanone diperoxide(yield 1 3 % …     

Hydrophobically directed selective reduction of ketones

Three hydrophobic borohydrides carrying phenyl, pentafluorophenyl, and beta-naphthyl groups were used to reduce ketones in water and in methanol. With ketones carrying phenyl, naphthyl, or biphenyl substituents, there was preferential reduction in methanol of competing acetyl groups, either intermolecular or intramolecular, but preferential reduction of the aryl ketones in water. In the most extreme case, there was a 40-fold selectivity reversal. Lithium borohydride showed no such change in selectivity and favored acetyl reduction in both solvents. Salt and cosolvent effects indicate that hydrophobic packing is involved in the reaction of hydrophobic reagents with the aryl ketones. Some special interaction of the pentafluorophenyl group with aryl rings was also detected.