氢氧化铯促进下硒、端炔及卤代烃反应合成炔硒醚

DMF作溶剂, 4Å分子筛存在下, 将端炔、CsOH、硒粉在室温搅拌2 h, 然后加入溴代烃或二芳基碘盐, 在室温下搅拌20 h, 得炔硒醚, 收率约60%. 反应机理为端炔与氢氧化铯作用形成炔化铯, 然后元素硒进行C—Cs键插入形成炔硒化铯, 炔硒化铯对溴代烃或二芳基碘盐进行亲核取代得到相应的炔硒醚     

锡促进的烯丙基硒醚和烯丙基硫醚的合成

在金属锡促进下，烯丙基溴与二硒醚或二硫醚反应，生成烯丙基硒醚或烯丙基硫醚 。     

三溴化金催化端炔与二芳基二硒醚反应合成炔基硒醚

炔基硒醚是合成一些有机硒化合物的重要起始物。本文研究发现,在三溴化金(Au Br3)催化下,端位炔和二芳基二硒醚在弱碱(如碳酸钾)存在下反应,生成炔基芳基硒醚,产率为69%~98%;在空气参与下,于80℃下进行反应,反应条件简单,且二硒醚的两个硒原子均可以被利用。二甲基亚砜(DMSO)是合适的溶剂,在极性较小的溶剂(如甲苯、四氢呋喃)中,此反应不能进行。芳基炔(如苯乙炔、对甲基苯乙炔、对氯苯乙炔等)、烯基炔(如环己烯乙炔)和烷基炔(如1-壬炔)均能顺利进行此反应。当芳基炔苯环的间位或邻位连有取代基时,反应产率较低(69%~82%),而对位无论是连有吸电子基还是给电子基,该反应均可以得到很高的产率(95%)。     

4,7-二噻吩-[2,1,3]苯并硒二唑的合成及其光电性能

苯并硫二唑经溴代,还原和闭环反应制得4,7-二溴[2,1,3]苯并硒二唑(3);以Pd(PPh3)2Cl2为催化剂,3与2-三丁基锡噻吩(4)经斯蒂尔偶联反应合成了4,7-二噻吩-[2,1,3]苯并硒二唑(5)。5为新化合物,其结构和性能经1H NMR,13C NMR,UV-Vis,荧光光谱法和循环伏安法表征。结果表明:5具有应用于光伏材料的带隙(12.2 e V);有较宽的吸收波长(260 nm~487 nm),在红光区域发射较强的荧光(620 nm);有可逆的氧化还原曲线,电化学性质稳定。     

1-氯甲基-4-氟-1,4-二氮杂双环[2.2.2]辛烷二(四氟硼酸盐)氧化二苯二硒醚:烯烃的苯硒化方法

在三氟甲磺酸银的催化下,二苯二硒醚被1-氯甲基-4-氟-1,4-二氮杂双环[2.2.2]辛烷二(四氟硼酸盐)(Selectfluor)氧化后,分别与1-己烯烃、苯乙烯或其衍生物加成;在含有水或醇(如甲醇、乙醇、异丙醇)的二氯甲烷中(二氯甲烷与水或醇的体积比为1∶1)反应,分别得到β-羟基或β-烷氧基苯硒醚,产率为72%~94%;探讨了反应条件及底物的适用范围。此方法具有反应条件温和、产率高的特点。     

氢氧化铯催化O,O-二烷基-Se-芳基磷酸酯的合成

在催化量氢氧化铯存在下,O,O-二烷基膦酸酯与二芳基二硒醚在DMSO中、室温、空气氛中反应,高收率得到磷酸硒酯.反应机理为氢氧化铯与O,O-二烷基膦酸酯反应生成的(RO)2P-(O)Cs+,(RO)2P-(O)Cs+亲核进攻ArSeSeAr生成磷酸硒酯和ArSe-Cs+,后者在水存在下,被氧化得到ArSeSeAr和氢氧化铯.这方法为合成磷酸硒酯提供了一条简便有效的路径.     

芳基硒代酰胺与α-卤代乙酸在醇中的硒转移反应——二烷氧羰基甲基二硒醚的简便合成

芳基硒代酰胺与氯乙酸在各种醇中无催化剂下以1∶1和1∶2的比例投入, 发生硒转移反应, 不同原料投入比下的反应生成了同一种C—Se—Se—C偶联产物——具有多功能团的二烷氧羰基甲基二硒醚, 提供了一种新的合成二烷氧羰基甲基二硒醚的简便方法, 且反应具有条件温和、产率高、原料易得和选择性好等优点. 为了研究该反应机理, 选择α-溴代乙酸甲酯或α-溴代乙酸乙酯在无催化剂、中性条件下, 乙醇溶液中与苯基硒代酰胺室温下反应, 投料比为1∶1和2∶1, 结果也都生成了同一类产物二甲氧羰基甲基二硒醚或二乙氧羰基甲基二硒醚, 同时还分离得到了相应的副产物苯甲酸乙酯. 对该C—Se—Se—C偶联反应发生的可能机理作了推测.     

青蒿素及其一类物结构和合成的研究——ⅩⅩⅣ.青蒿素转化为天然的△~(11(13))-脱氢青蒿素(英文)

本文首次报道从青蒿素(2)转变为△~(11(13))-脱氢青蒿素(1)的结果。青蒿素(2)在 LDA 存在下,与溴苯硒反应,得到11-苯硒基青蒿素(3)(27％)、11-溴代青蒿素(4)(15％),△~(11(13))-脱氢青蒿素(1)和△~(7(11)-脱氢青蒿素(5)(46％)。用二苯二硒的硒化反应只回收原料青蒿素。3用30％H_2O_2氧化,生成天然的1,产率95％。根据CD 光谱,推定3中的苯硒基和4中的溴原子均处于α-构型。     

Pd(OAc)_2/CuI分步催化合成多取代3-烃硫(硒)基吲哚化合物（英文）

发展了一种Pd(OAc)_2/CuI分步催化2-(2,2-二溴乙烯基)胺、苯硼酸和联硫(硒)化合物发生偶联/环化/硫烷基化反应合成3-烃硫(硒)基吲哚化合物的新方法.底物中不同的官能团,如甲氧基、氯、三氟甲基在反应中都能很好地兼容.     

血吸虫病化学治疗的研究Ⅳ.二巯基丙醇的芳基醚及其锑硫醇鹽

对位上具有不同取代基团的芳某丙烯基醚加溴生成相应的芳基、2,3-二溴丙基醚。这些新化合物与硫化氫鉀(或鈉)作用,其中对甲基、对溴及对氨基苯基、2,3-二溴丙基醚形成相应的2,3-二巯基丙基醚;对羧基化合物在冷甲醇液中也可形成二巯基化合物,但在冷水溶液中不起作用,热水溶液中則醚鍵發生水解,不能生成二巯基丙基醚;对硝基及对磺酰氨基化合物在甲醇液中冷时作用醚鍵也遭致水解。制得的四种二巯基丙醚与三氯化銻作用,并再將氯原子水解为羟基,生成相应的4-芳氧甲某-4,5-二氫-2-羟基-1,3-二間硫銻杂茂(4-Aryloxymethyl-4,5-dihydro-2-hydroxy-1,3-dithiastibiol)。     

(NO3)3CeBrO3: Solvent‐Free Oxidation of Alcohols and Deprotection and Oxidative Deprotection of Trimethylsilyl Ethers

Trinitratocerium(IV) bromate (TNCB) can be used as an efficient reagent for oxidation of alcohols and deprotection and oxidative deprotection of trimethylsilyl ethers under solvent‐free conditions.     

Alcohols and di-tert-butyl dicarbonate: how the nature of the Lewis acid catalyst may address the reaction to the synthesis of tert-butyl ethers

The reaction between alcohols and Boc2O leads to the formation of tert-butyl ethers and/or Boc-alcohols, depending on the nature of the Lewis acid catalyst. Product distribution is mainly tuned by the anionic part of the salt. Perchlorates and triflates, anions with highly delocalized negative charge, give prevalent or exclusive ether formation. On the other hand, Boc alcohols are the main or exclusive products with un-delocalized isopropoxide or low-delocalized acetate ions. The metal ion influences only the reaction rate, roughly following standard parameters for calculating Lewis acidity. A reaction mechanism is supposed, and a series of experimental evidences is reported to support it. These studies allowed us to conclude that, to synthesize tert-butyl ethers, in reactions involving aliphatic alcohols, Mg(ClO4)2 or Al(ClO4)3 represents the best compromise between costs and efficiency of the reaction, while, in reactions involving phenols, Sc(OTf)3 is the best choice, since aromatic tert-butyl ethers are not stable in the presence of perchlorates.     

Efficient oxidative deprotection of trimethylsilyl, tetrahydropyranyl and methoxymethyl ethers under solvent-free conditions

A mild, efficient and fast method for direct oxidation of trimethylsilyl, tetrahydropyranyl and methoxymethyl ethers to their corresponding carbonyl compounds using trinitratocerium（Ⅳ） bromate （TNCB） supported on NaHSO4.H2O under solvent-free conditions is reported.     

12-Tungstophosphoric acid supported on inorganic oxides as heterogeneous and reusable catalysts for the selective preparation of alkoxymethyl ethers and their deprotections under different reaction conditions

A wide variety of primary and secondary alcohols were efficiently converted to their corresponding methoxymethyl (MOM) and ethoxymethyl (EOM) ethers in the presence of catalytic amounts of supported H₃PW₁₂O₄₀ on silica gel and zirconia at room temperature and under microwave irradiation at solvent-free conditions, whereas, phenols and tertiary alcohols remained intact under the same reaction conditions. Deprotection of these ethers to their parent alcohols was also achieved using these heterogeneous catalysts in ethanol, as a green solvent, under reflux conditions and microwave irradiation. Selective deprotection of primary and secondary MOM- and EOM-ethers in the presence of phenolic and tertiary ones, methyl and benzyl ethers, esters and trimethylsilyl ethers was achieved by these reagent systems. The present methodology offers several advantages such as short reaction times, high yields, simple procedure, heterogeneous reaction conditions, selectivity, non-toxicity and reusability of the catalysts.     

Mass spectra of alkenyl methyl ethers

Electron impact ionization mass spectra of numerous alkenyl methyl ethers C_nH_2n-1OCH₃ (n = 3–6) recorded under normal (4 kV, 70 eV, 175°C) and low-energy, low-temperature (8 kV, 12 eV, 75 °C) conditions are reported. The influence of the position and stereochemistry of the double bond on the dissociation of ionized alkenyl methyl ethers is discussed. The mechanisms by which these ethers fragment after ionization have been further investigated using extensive ²H-labelling experiments and by studying the energy dependence of the reactions. Ethers of allylic alcohols show spectra that are distinct from those of the isomeric species in which the double bond is separated by one or more sp³ carbon atoms from the carbon atom carrying the methoxy group. Three principal primary fragmentations are observed. The most common process, especially for ionized ethers of allylic alcohols, is loss of an alkyl group. This reaction often occurs by simple α-cleavage of radical-cations of the appropriate structure; however, alkyl groups attached to either end of the double bond are also readily lost. These formal β- and γ-cleavages are explained in terms of rearrangements via distonic ions and, at least in the case of γ-cleavages, ionized methoxycyclopropanes. Ionized homoallyl methyl ethers tend to eliminate an allylic radical, particularly at high internal energies, with formation of an oxonium ion (CH₃ ⁺O?CH₂ or CH₃ ⁺O?CHCH₃). The ethers of linear pentenols and hexenols show abundant [M - CH₃OH]⁺? ions in their spectra, especially when a terminal methoxy group is present Methanol loss also takes place from ionized ethers of allylic alcohols in which there is a Δ-hydrogen atom; this process is significantly favoured by cis, rather than trans, stereochemistry of the double bond.     

Absolute rate constants for some hydrogen atom abstraction reactions by a primary fluoroalkyl radical in water

A combination of laser flash photolysis and competitive kinetic methods have been used to measure the absolute bimolecular rate constants for hydrogen atom abstraction in water from a variety of organic substrates including alcohols, ethers, and carboxylic acids by the perfluoroalkyl radical, *CF(2)CF(2)OCF(2)CF(2)SO(3)(-) Na(+). Comparison, where possible, of these rate constants with those previously measured for analogous reactions in the non-polar organic solvent, 1,3-bis(trifluoromethyl)benzene (J. Am. Chem. Soc, 1999, 121, 7335) show that the alcohols react 2-5 times more rapidly in the water solvent and that the ethers react at the same rate in both solvents. A transition state for hydrogen abstraction that is more reminiscent of an "intimate ion pair" than a "solvent separated ion pair" is invoked to explain these modest solvent effects.     

Lewis acid-mediated highly regioselective SN2-Type ring-opening of 2-aryl-N-tosylazetidines and aziridines by alcohols

Lewis acid-mediated highly regioselective SN2-type ring-opening of 2-aryl-N-tosylazetidines with alcohols to afford various 1,3-amino ethers in excellent yields with good enantiomeric excess is described. Similar SN2-type ring-opening of chiral 2-phenyl-N-tosylaziridine with various alcohols produces the corresponding nonracemic 1,2-amino ethers in excellent yields and good ee. The mechanism of the ring-opening of aziridines and azetidines via an SN2 pathway is supported by the formation of nonracemic amino ethers.     

Monobromination of Activated Aromatic Compounds with Polyvinylbenzyltriphenylphosphonium Supported Tribromide

Chloromethylated crosslinked co‐polyvinylbenzene‐divinylbenzene (2% DVB) was treated with triphenylphosphine and then with sodium bromate and hydrobromic add to afford red colored insoluble polyvinylbenzyltriphenylphosphonium supported tribromide. This reagent could be used as a mild and efficient monobrominating reagent for activated aromatic compounds such as phenols, aromatic ethers, aromatic amines and acetylanilines with good yields and high para‐selectivity.     

Oxidation of organic compounds by polymer-supported bromate ion

Aromatic aldehydes, secondary alcohols and thiophenol have been oxidized by polymer-supported bromate ion under mild reaction conditions to give the oxidized products in high yields and purities.     

Polystyrene‐Gallium Trichloride Complex: A Mild,Highly Efficient,and Recyclable Polymeric Lewis Acid Catalyst for Chemoselective Silylation of Alcohols and Phenols with Hexamethyldisilazane

Polystyrene‐supported gallium trichloride (PS/GaCl₃) as a highly active and reusable heterogeneous Lewis acid effectively activates hexamethyldisilazane (HMDS) for the efficient silylation of alcohols and phenols at room temperature. In this heterogeneous catalytic system, primary, secondary, and tertiary alcohols as well as phenols were converted to their corresponding trimethylsilyl ethers with short reaction times and high yields under mild reaction conditions. The heterogenized catalyst is of high reusability and stability in the silylation reactions and was recovered several times with negligible loss in its activity or a negligible catalyst leaching, and also there is no need for regeneration. It is noteworthy that this method can be used for chemoselective silylation of different alcohols and phenols with high yields.