Trifluoromethyl-stabilized optically active oxiranyl and aziridinyl anions for stereospecific syntheses of trifluoromethylated compounds

Optically active 2,3-epoxy-1,1,1-trifluoropropane was converted into the corresponding oxiranyl anion and reacted with electrophiles such as aldehydes, ketones and halides to give the corresponding adducts in moderate to good yields. The whole reaction occurred with retention of configuration at the stereogenic carbon center. In a similar manner, trifluoromethyl stabilizing aziridinyl anions were generated from the optically active N-tosyl and N-anisyl-2-trifluoromethylaziridines. They also reacted well with various electrophiles. The products of these reactions are versatile synthetic intermediates useful for the synthesis of a variety of trifluoromethylated compounds with quaternary chiral carbon centers.     

Synthesis of trans-fused polycyclic ethers with angular methyl groups using sulfonyl-stabilized oxiranyl anions

An efficient method has been developed for the synthesis of trans-fused tetrahydropyrans with angular methyl groups adjacent to the ring oxygen. The procedure involves the coupling reaction of a sulfonyl-stabilized oxiranyl anion with an appropriate triflate followed by 6-endo cyclization, and is effective for the construction of 6/6- and 6/7/6-cyclic ether ring systems with sterically congested 1,3-diaxial methyl groups.     

Gas-phase reactions of halogenated radical carbene anions with sulfur and oxygen containing species

The reactivities of mono- and dihalocarbene anions (CHCl⁻, CHBr⁻, CF₂⁻, CCl₂⁻, and CBrCl⁻) were studied using a tandem flowing afterglow-selected ion flow tube instrument. Reaction rate constants and product branching ratios are reported for the reactions of these carbene anions with six neutral reagents (CS₂, COS, CO₂, O₂, CO, and N₂O). These anions were found to demonstrate diverse chemistry as illustrated by formation of multiple product ions and by the observed reaction trends. The reactions of CHCl⁻ and CHBr⁻ occur with similar efficiencies and reactivity patterns. Substitution of a Cl atom for an H atom to form CCl₂⁻ and CBrCl⁻ decreases the rate constants; these two anions react with similar efficiencies and reactivity trends. The CF₂⁻ anion displays remarkably different reactivity; these differences are discussed in terms of its lower electron binding energy and the effect of the electronegative fluorine substituents. The results presented here are compared to the reactivity of the CH₂⁻ anion, which has previously been reported.     

Halide anions are formed from reactions between atomic metal anions and halogenated aromatic molecules

Atomic metal anions (AMAs) Fe^–, Cs^–, Cu^– and Ag^– were generated in the gas phase by collisionally decomposing the corresponding metal‐oxalate anion. Mass selected AMAs were allowed to react with halogenated and nitrated molecules (C6H5Cl, C6H4Cl2, C6H3Cl3, C6H5I, C6H5Br and C6H5NO2) in the collision hexapole of a triple‐quadrupole mass spectrometer. Observed reactions include the predominant formation of X^– (X = Cl, Br and I), as well as FeCl^–, FeCl2^– and FeCl3^– when Fe‐ reacted with the mono, di and tri‐chlorobenzenes; reactions between 1,4‐dichlorobenzene and Cs^– produced Cl^–, CsCl^– and CsCl2^–; reactions involving iodobenzene also produced, CsI^–, CsI2^– and AgI^–. The results suggest that the reaction to form X^– (X = Cl, Br, I and NO2) may be a promising route to improving the detection efficiency by mass spectrometry for such analytes. Copyright © 2016 John Wiley & Sons, Ltd.     

Reaction of sulphate radical anion (SO<Superscript>.</Superscript><Subscript>4</Subscript><Superscript>-</Superscript>) with hydroxy-and methyl-substituted pyrimidines: a pulse radiolysis study

Reactions of sulphate radical anion (SO·₄ ^-) with 4,6-dihydroxy-2-methyl pyrimidine (DHMP), 2,4-dimethyl-6-hydroxy pyrimidine (DMHP), 6-methyl uracil (MU) and 5,6-dimethyl uracil (DMU) have been studied by pulse radiolysis at pH 3 and at pH 10. The transient intermediate spectra were compared with those from the reaction of hydroxyl radical (·OH). It is proposed that SO·₄ ^- produces radical cations of these pyrimidines in the initial stage. These radical cations are short-lived except in the case of DMHP where a relatively longer lived radical cation is proposed to be formed. When there is a hydrogen atom attached to the N(1) or N(3) position, a deprotonation from these sites is highly favored. When there is no hydrogen attached to these sites, deprotonation from a substituted methyl group is favored. At acidic pH, deprotonation from nitrogen is observed for DHMP, MU and DMU. At basic pH, the radical cation reacts with OH^- leading to the formation of OH adducts.     

双酰腙钳形受体分子的合成及阴离子识别研究

在微波辐射下快速、高产率地合成了一系列含有四唑环的双酰腙受体,并对其进行了元素分析、红外以及核磁共振氢谱和碳谱表征.利用紫外-可见吸收光谱及1HNMR考察了其与F-,Cl-,Br-和I-卤素阴离子的相互作用.紫外滴定实验表明4a较4b,4c对F-有更好的识别作用.Job曲线表明,主体4a与F-间形成1∶1型氢键络合物.通过1HNMR滴定及质子溶剂效应进一步证明了该受体分子与阴离子以氢键作用相结合.     

Critical importance of leaving group ‘softness’ in nucleophilic ring closure reactions of ambident anions to 1,2-diazetidines

Highly strained, four-membered 1,2-diazetidine rings are produced in good yields (50-98%) in nucleophilic ring closure reactions provided ‘soft’ leaving groups such as iodide are used, a finding that can be rationalised in terms of the Hard Soft Acids and Bases principle.     

5-芳基-2-呋喃甲酰基氨基硫脲类衍生物的合成及水溶液中 阴离子识别研究

合成了一系列未见文献报道的5-芳基-2-呋喃甲酰基氨基硫脲类衍生物, 通过1H NMR, IR, 元素分析确认了其结构. 并利用紫外-可见吸收光谱考查了它们在DMSO及DMSO/H2O溶液中与F－, Cl－, Br－, I－, CH3COO－, , 等阴离子的识别作用. 结果表明: 该类受体分子能较好地识别F－, CH3COO－, 三种阴离子, 当加入这三种阴离子后, 溶液的颜色由淡黄色转变为亮黄色. 通过改变含水量可有效地调控识别作用的选择性. 1H NMR滴定实验进一步证实了受体分子与阴离子通过氢键作用形成主客体配合物.     

Self‐crosslinking borate anions for the production of tough UV‐cured polyelectrolyte surfaces

The first anion with four polymerizable groups has been synthesized and used to produce durable, crosslinked polyelectrolyte (PE) coatings in a single step. Sodium tetrakis(4‐vinylphenyl)borate (NaBSty₄) was produced by the reaction of BCl₃ and the Grignard of 4‐bromostyrene. The full series of borates NaBPh_xSty_4?x, x = 1?3, were also synthesized analogously by reaction of the styryl‐Grignard and PhBCl₂, Ph₂BCl, or Ph₃B. Anion exchange of the borates with tributyl 4‐vinylbenzylphosphonium chloride gave a family of organic salts developed for applications in photopolymerized coatings. The percent UV cure of the polymer films was determined by infrared spectroscopy and this relative level of curing was corroborated by differential scanning calorimetry analysis. The degree of crosslinking imparted to the polymer films by the different monomers has resulted in varied mechanical properties, which were probed by diamond tip scratch tests and nanoindentation. These clearly demonstrated that as the number of polymerizable groups increased, the film hardness increased correspondingly. The final hardness of the films exceeds those of other related systems and identifies styryl borates as viable crosslinking additives in UV curable technologies, especially in the production of durable PE films. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Hydrozirconation of lithium alkynylselenolate anions. Generation and reactions of alpha-zirconated vinyl selenide intermediates

Lithium alkynylselenolate anions react completely with 1.0 equiv of Cp(2)Zr(H)Cl in THF at room temperature to give exclusively the alpha-zirconated vinylselenolate intermediates 23-27, which by treatment with an alkyl halide afforded the alpha-zirconated vinyl alkylselenide intermediates 29-33. Reaction of 29-33 with butyltellurenyl bromide results in the formation of ketene telluro(seleno) acetals 35-39 with total control of the regio- and stereochemistry. The synthetic utility of the ketene telluro(seleno) acetals obtained here was demonstrated by reaction of 36 with butyllithium. This promotes the exclusive and stereospecific removal of the tellurium moiety and enables formation of the corresponding selenium-containing allylic alcohol of type 44, alpha-(alkylseleno)-alpha,beta-unsaturated aldehyde 45, ester 46, or carboxylic acid 47, after reaction with different types of electrophiles.     

Silicon‐Based Bulky Group‐Induced Remote Control and Conformational Preference in the Synthesis and Application of Isolable Atropisomeric Amides with Secondary Alcohol or Amine Moieties

Remote stereocontrol through conformational transmission along a carbon chain is highly important in synthetic systems and molecular architectures. In this work, the interactional reactivity between a remote silicon‐based bulky group and an O‐/N‐containing functional group has been revealed and determined by lateral lithiation–substitution, desilylation, as well as desilylation–olefination with benzaldehyde. The results suggest considerable information transmission and steric hindrance that can be exploited for the controllable synthesis of atropisomeric molecules. Based on the remote steric effect of a functional group across the aromatic ring of an amide, the construction of isolable atropisomeric amides with functional groups, such as alcohol, amine, and olefin was successfully achieved. All these new atropisomers were obtained in reasonable yield in pure diastereomeric form, and the specific configuration of representative products was confirmed by X‐ray crystallography.     

A novel chemosensor based on Fe(III)-complexation for selective recognition and rapid detection of fluoride anions in aqueous media

A novel fluorogenic receptor 1 was prepared by the reaction of thiosemicarbazide with 1-naphthaldehyde. Based on in situ-formed 1-Fe(III) complexes having the specific binding affinity for F⁻ anions, this sensory system allows rapid recognition and quantitative detection of fluoride in neutral aqueous media in an ‘off-on’ fashion. The fluoride measurement method not only exhibits a low detection limit but also has strong anti-interference ability to common coexisting ions, as evidenced by competitive experiments.     

Generation and reactions of substituted phenide anions in an electrospray triple quadrupole mass spectrometer

Substituted benzoic acid anions undergo decarboxylation in the medium-pressure region of an electrospray ion source yielding in most cases the correspondingly substituted phenide anions in high yield. The location of the anionic center is specified by the position of the carboxylic group. The only exceptions are compounds with substituents containing acidic hydrogen atoms, like OH and NH(2) groups. For such compounds, either an intra- or an intermolecular (mediated by the molecules of methanol or water) proton transfer from the more acidic position to the benzene ring is observed. The generated anions can be selected using the first quadrupole for studying their ion-molecule chemistry in the second quadrupole of a triple quadrupole mass spectrometer. Their reactions with CO(2), O(2), CH(3)COCH(3) and CCl(4) may serve as typical examples. The general applicability of this method for the generation of phenide anions has been confirmed on three different mass spectrometers. Experiments performed using carboxylic acids other then benzoic acid and its derivatives show that this method is not limited to phenide anions and can be used for the generation of a much wider range of carbanions in the gas phase.     

Stability of polyhedral borane anions and carboranes

Polyhedral borane anions and carboranes that can be constructed formally from the interaction of rings and caps will be stable with six interstitial electrons. Interstitial electron count is obtained by summing the number of π electrons of the ring and the electrons of the caps involved in ring cap binding. Thus B₇H₇ ⁻² (D_5h) has 6 interstitial electrons (none from the B₅H₅ ring, two each from the twobh caps and two negative charge),mndo calculations on isoelectronic pyramidal molecules B₆H₆ ⁻⁴ (C_5v), B₅H₅CH⁻³ (C_5v), B₅H₅ ⁻⁴ (C_4v), B₄H₄CH⁻³ (C_4v), B₄H₄ ⁻⁴ (T _d) and B₃H₃CH⁻³ (C_3v) suggests a criterion based on the out-of-plane bendings of the ring B-H bonds to select the best combination of borocycles and BH or CH caps. Three-membered borocycle prefers CH cap, five-membered borocycle prefers BH cap. The preference of four-membered ring for BH or CH cap is not as pronounced. The extra stability of B₁₂H₁₂ ⁻² arises from the geometry of the icosahedron. The relative stabilities ofnido andcloso carboranes follow from these rules.     

The first one-pot ‘alkane-like’ reactions of carbonyl-containing adamantanes

A novel ‘alkane-like’ methodology for the direct and very simple one-pot functionalization of amides and an ester of 1-adamantanecarboxylic acid provides access to new and synthetically challenging 1,3-dicarbonyl-containing adamantanoid compounds with the same or different functional groups.     

Studies of intramolecular alkylidene carbene reactions; an approach to heterocyclic nucleoside bases

A series of investigations into the applications of intramolecular cyclisations of alkylidene carbenes are described. The insertion reaction of the carbene generated from 1,4-di(tert-butyldimethylsilyloxy)-3-benzyloxy-butane-2-one to the benzylic position proceeded in good yield and a diastereoselectivity of 3.6:1. The corresponding insertion process of 1,4-di(tert-butyldimethylsilyloxy)-3-methyloxymethyl-butane-2-one gave a mixture of products, including one resulting from a competitive trapping of the carbene by the oxygen atom of a silyloxy group.     

Synthesis of di-substituted calix[4]arene-based receptors for extraction of chromate and arsenate anions

The article describes the synthesis of a family of novel calix[4]arene ionophores, 25,27-bis-(2-aminomethylpyridine-propoxy)-26,28-dihydroxycalix[4]arene (5a), 25,27-bis-(3-aminomethylpyridine-propoxy)-26,28-dihydroxycalix[4]arene (5b) and two chromogenic calix[4]arenes, 5,17-dinitro-25,27-bis-(2-aminomethylpyridine-propoxy)-26,28-dihydroxycalix[4]arene (5c), 5,17-dinitro-25,27-bis-(3-aminomethylpyridine-propoxy)-26,28-dihydroxycalix[4]arene (5d) bearing pyridinium units. In the synthesis, the upper and lower rims of p-tert-butylcalix[4]arene were modified in order to acquire binding sites for the recognition of arsenate and dichromate anions. It has been observed that protonated alkylammonium forms of the ionophores showed high affinity toward dichromate and arsenate anions.