Organic Reactions in the Solid State: Reactions of Enclathrated 3,4-Epoxycyclopentanone (=6-Oxobicyclo[3.1.0]hexan-3-one) in Tri-o-thymotide and Absolute Configuration of 4-Hydroxy- and 4-Chlorocyclopent-2-en-1-one

Several aspects of the heterogeneous actions of aqueous and gaseous HCl on the chemical behavior of 3,4-epoxycyclopentanone (=6-oxabicyclo[3.1.0]hexan-3-one; 1 ) included in the asymmetric cages of tri-o-thymotide (TOT) clathrates belonging to space groups P3₁21 are described, showing specific features strikingly at variance with those observed in liquid solutions. In a first step, the substrate underwent an acid-promoted allylic isomerization, as already observed in our previous investigations, to give optically active 4-hydroxycyclopent-2-en-1-one ( 2 ). In a consecutive step, a displacement of the OH group was accomplished by the Cl⁻ anion to afford the corresponding chloro compound 3 . Polymorphism was encountered in the preparation of TOT/ 1 clathrates. Recrystallization of TOT in the pure guest 1 yielded micro-twinned crystals belonging to the P3₁ space group (host/guest ratio 1 : 1), whereas the expected P3₁21 lattice grew from a mixture of TOT, 1 , and MeOH. The structural determination of TOT/ 1 was carried out by X-ray diffraction (Fig. 1). Kinetic measurements were achieved that shed light on some striking features of this type of heterogeneous reactions for solid-liquid and solid-gas systems. Several reactions of pure clathrate antipodes (+)-TOT/ 1 with gaseous HCl were carried out under various conditions; concentration and enantiomer-excess(ee) determinations of the products 2 and 3 allowed to establish a larger ee for 3 , thus demonstrating the influence of the host-guest diastereomeric association on the progression of the reaction. The correlation of optical activities of the host and products for the global reaction disclosed the sequence (+)-(M)-TOT/ 1 →(−)- 2 →(−)- 3 . A new way for the preparation of 2 was devised. It was further demonstrated that the X-ray structure analysis of the chiral clathrate (M)-TOT/(+)- 2 (Fig. 4) associated with chiroptical measurements was an efficient and straightforward method to determine the absolute (+)-(R)-configuration of the guest. The enantioselectivity of the TOT clathrate for 2 was established by two different methods which allowed the appraisal of an accurate revised value of the specific rotation of 2 . The enclathration of 3 occurred exclusively in the orthorhombic centrosymmetric host lattice Pbca, thus prohibiting the X-ray structural determination of the guest absolute configuration. The problem of finding a pathway to the intended enantiomer enrichment of 3 was worked out through the action of aqueous HCl on microcrystalline (+)-TOT/(−)-(S)- 2 that gave an optically active mixture of unreacted 2 with 3 as sole product. The pure optically active 3 was isolated by subsequent TLC. The resolution of 3 was achieved by GC over a chiral column and its (unknown) specific rotation measured. The absolute configuration of 3 was established by the measurement of the enantiomer purity of the optically active mixture 3 obtained after the total conversion of (−)-(S)- 2 in the presence of thionyl chloride in Et₂O, dioxane, and benzene. It was deduced that the (−)- 3 enantiomer had the (S)-configuration.     

Stereospecific reactions and interactions in tri-ortho-thymotide clathrates

The emphasis in this paper is on the interpretation of physicochemical phenomena occurring in tri-ortho-thymotide (TOT) clathrates in the light of crystallographic data.Enantiomeric discrimination of guest included in the cageP3₁21 clathrates, first suggested by H. M. Powell, has been studied for about twenty guest molecules. Practical applications include preparative resolution and determination of the absolute configuration of guest molecules via TOT clathrates. The observation of similar position and orientation within the cage of stereochemically related guests, provides a clue for the chiral discrimination in terms of crystallographic data. The influence of different factors (guest size, crystallographic disorder, etc.) is analyzed, as well as the difficulties in obtaining a precise assignment of the chirality of host/guest interactions.TOT clathrates including stilbene and cinnamic acid as guest undergo photoisomerization reactions whose pathway is different from that observed in solution or in the pure guest crystal, due to the different microenvironment around the olefinic molecule.It is shown that symmetry, as well as crystallographic disorder, is the most important factors governing these phenomena. The analysis of these factors bears similarities with the problems arising in chiral discrimination. In particular, the flexibility of the TOT molecule is probably strongly correlated with the physicochemical phenomena so far studied, as well as with the large variety of crystal forms. The comparison of the TOT molecular configurations in five different crystallographic environments allows a critical discussion on the pertinent molecular parameters which reflect the TOT flexibility.Dedicated to Professor H. M. Powell.     

Infinite dilution activity coefficents of hydrocarbons in tetra-n-alkyltin solvents between 40 and 60°C measured by gas-liquid chromatography

Infinite dilution activity coefficients for twenty-three hydrocarbons in tetra-n-amyltin (TAT) and in tetra-n-lauryltin (TLT) at several temperatures between 40 and 60°C were measured by gas liquid chromatography. The results, together with those obtained in an earlier paper in tetra-n-octyltin (TOT), are compared and discussed in terms of the equation of state theory of Flory and of the lattice fluid theory of Sanchez and Lacombe.     

Validity of the Hammond postulate and constraints on general one-dimensional reaction barriers

The Hammond postulate is a useful, qualitative tool that interrelates structural similarities between reactants, transition structures, and products with the exo- or endothermicity of reactions. It applies to most chemical reactions, although several exceptions are known. In this study the following problem is addressed: is it possible to formulate conditions for the validity of the quantitative Hammond postulate in terms of simple physical quantities characteristic to the molecules involved? A detailed analysis is given for the conditions of validity of the postulate, in terms of bounds on the internal forces and force constants of nuclear arrangements encountered along a reaction path. We have determined a broad class of constraints on barrier shapes that must be satisfied in order to obtain a critical situation that violates the Hammond postulate: a reactant-like transition structure (“transition state”) for endothermic reactions, and a product-like one for exothermic reactions. The general constraints are formulated in terms of physically meaningful quantities: (i) energy differences, (ii) restrictions on slopes (e.g., an upper bound on internal forces), and (iii) restrictions on curvatures (e.g., upper bounds on force constants) along potential curves.     

Reactive orbital energy theory serving a theoretical foundation for the electronic theory of organic chemistry

It is established that the reactive orbital energy theory (ROET) theoretically reproduces the rule-based electronic theory diagrams of organic chemistry by a comparative study on the charge transfer natures of typical organic carbon–carbon and carbon–heteroatom bond formation reactions: aldol, Mannich, α-aminooxylation, and isogyric reactions. The ROET, which is an expansion of the reaction electronic theories (e.g., the frontier orbital theory) in terms of orbital energies, elucidates the reactive orbitals driving reactions and the charge transferability indices of the reactions. Performing the ROET analyses of these reactions shows that the charge transfer directions given in the rule-based diagrams of the electronic theory are reproduced even for the functional groups of charge transfer destinations in all but only two processes for 38 reaction processes. The ROET analyses also make clear the detailed orbital-based pictures of these bond formation reactions: that is, the use of the out-of-plane antibonding π orbitals in acidic conditions (enol-mode) and in-plane antibonding π orbitals in basic conditions (enolate-mode), which explain the experimentally assumed mechanisms such as the π-bond formations in acidic conditions and σ-bond formations at α-carbons in basic conditions. Furthermore, the ROET analyses explicate that the methyl group initially accepts electrons and then donates them to the bond formations in the target reactions. It is, consequently, suggested that the ROET serves a theoretical foundation for the electronic theory of organic chemistry.     

Alkylations of Chiral Nickel(II) Complexes of Glycine under Phase‐Transfer Conditions

Alkylation reactions of nickel(II) complex 6 derived from glycine and 2‐[(1‐benzyl‐L ‐prolyl)amino]benzophenone (BPBP) were studied under phase‐transfer‐catalysis (PTC) conditions. The goal of this work was to find an alternative suitable solvent for these reactions to replace the commonly used CH₂Cl₂ which leads to the formation of several by‐products, thus lowering the yield of target compounds. We demonstrate that 1,2‐dichloroethane is a markedly better solvent providing higher yields (75–99%) of the desired products 10 with 36–88% diastereoisomer purity (Scheme 3 and Table). Furthermore, we show that the stereochemical outcome of these PTC reactions (kinetic control) can be easily improved to >95% de by treatment of the PTC products with MeONa/MeOH. The scope of these reactions includes alkylations with methyl iodide as well as activated halides such as benzyl, allyl or propargyl, bromides and most notably ethyl 2‐bromoacetate (Table).     

Tailoring Magnetic Features in Zigzag-Edged Nanographenes by Controlled Diels–Alder Reactions

Nanographenes (NGs) with tunable electronic and magnetic properties have attracted enormous attention in the realm of carbon-based nanoelectronics. In particular, NGs with biradical character at the ground state are promising building units for molecular spintronics. However, most of the biradicaloids are susceptible to oxidation under ambient conditions and photolytic degradation, which hamper their further applications. Herein, we demonstrated the feasibility of tuning the magnetic properties of zigzag-edged NGs in order to enhance their stability via the controlled Diels–Alder reactions of peri-tetracene ( 4-PA ). The unstable 4-PA (y₀=0.72; half-life, t_1/2=3 h) was transformed into the unprecedented benzo-peri-tetracenes ( BPTs ) by a one-side Diels–Alder reaction, which featured a biradical character at the ground state (y₀=0.60) and exhibited remarkable stability under ambient conditions for several months. In addition, the fully zigzag-edged circumanthracenes ( CAs ) were achieved by two-fold or stepwise Diels–Alder reactions of 4-PA , in which the magnetic properties could be controlled by employing the corresponding dienophiles. Our work reported herein opens avenues for the synthesis of novel zigzag-edged NGs with tailor-made magnetic properties.     

Metal- and Solvent-Free Transesterification and Aldol Condensation Reactions by a Homogenous Recyclable Basic Ionic Liquid Based on the 1,3,5-Triazine Framework

A new recyclable basic ionic liquid was introduced as an efficient catalyst for aldol condensation and transesterification reactions under environmentally friendly conditions. The catalyst was prepared based on methyl imidazolium moieties bearing hydroxide counter anions via the Hofmann elimination on a 1,3,5-triazine framework. The ionic liquid with two functionalities including anion stabilizer and high basicity, was used as an efficient catalyst for aldol condensation as well as transesterification reaction of a variety of alkyl benzoates. All reactions were performed in the absence of any external reagent, co-catalyst, or solvent, in line with environmental protection. The kinetics isotope effect (KIE) was conducted for the transesterification reaction to elucidate the mechanism and rate determining step (RDS). It worth noted that, the homogeneous catalyst could be recycled from the reaction mixture and reused for several consecutive runs with insignificant drop of basicity and conversion.     

Study on modification of polymers with the aid of the Schmidt reaction

A study of the Schmidt reaction on several polymers with pendant carboxylic and ketone moieties was carried out. Four polymers were used as starting materials: (1) poly(methyl vinyl ketone), (2) poly(acrylic acid), (3) a copolymer of methyl vinyl ketone and acrylic acid, and (4) a copolymer of styrene and acrylic acid. Most reactions were conducted in an acetic acid medium with the exception of one reaction on poly(acrylic acid) which was done in dioxane and another on copolymer of styrene and acrylic acid done in chloroform. It was found that a Schmidt reaction on poly(acrylic acid) in acetic acid solution will lead to intermolecular reactions of the intermediate with the solvent in preference to reactions with neighboring carboxyl groups on the polymer backbone. A tendency of poly(acrylic acid) to form cyclic anhydrides under these reaction conditions interferes with the yield of acetamide units.     

Direct monitoring of protein-chemical reactions utilising nanoelectrospray mass spectrometry

The feasibility of nanoelectrospray mass spectrometry (nanoESI) for the direct analysis of protein chemical reactions and structural changes of proteins has been evaluated. Taking advantage of the long spraying time and the capability of nanoESI for employing a wide range of solvent conditions such as buffers and detergents, applications of monitoring reaction pathways, and dynamics have been carried out with several peptides and proteins. The time course of proteolytic digestions with trypsin and pepsin was investigated for several model polypeptides, and nanoESI showed to provide an efficient tool for optimising digestion conditions for the mass spectrometric peptide mapping analysis. Examples of specific protein chemical modification reactions at arginine and tyrosine residues illustrate the feasibility of nanoESI to monitoring reaction yields and modification sites for more than 180 min. Furthermore, changes of the pattern of protonated molecules caused by temperature effects and by protein unfolding due to disulfide bond reduction have been studied with the model proteins cytochrome c and hen eggwhite lysozyme. The results indicate that nanoESI is an efficient technique for the direct, molecular characterisation of protein-chemical reactions in solution.     

Dithiirane or thiosulfine intermediates in the reaction of acetyl diaroylchloromethyl disulfides with secondary amines?

Summary Since 1979,Senning's acetyl dibenzoylchloromethyl disulfide has been known as one of the first thiosulfine/dithiirane precursors. Its reactions with an excess of morpholine fulfill three advantageous conditions at once: thiosulfine or dithiirane species are intercepted by intermolecular additions, without heating, and without rearrangements. In the present work, reactions between a series of new acetyl diaroylchloromethyl disulfides ((4-X-C₆H₄-CO)₂-CCl-SSCOCH₃;X=F, Cl, Br, CH₃, and CH₃O) and an excess of morpholine are studied. As dominating products, 2-(4-morpholinyldithio)-1,3-diaryl-1,3-propanediones are obtained. The reactions are complete within several seconds. In order to obtain high yields of interception products, the mixtures have to be worked up within a few minutes. From the observation of high reaction rates at room temperature, a new reaction mechanism is deduced that involves the initial formation of dithiirane species (alone or before thiosulfine species).Dedicated to Prof.Peter K. Claus on the occasion of his 60th birthday     

Dealkenylative Alkenylation: Formal σ-Bond Metathesis of Olefins

The dealkenylative alkenylation of alkene C(sp³)−C(sp²) bonds has been an unexplored area for C−C bond formation. Herein 64 examples of β-alkylated styrene derivatives, synthesized through the reactions of readily accessible feedstock olefins with β-nitrostyrenes by ozone/Fe^II-mediated radical substitutions, are reported. These reactions proceed with good efficiencies and high stereoselectivities under mild reaction conditions and tolerate an array of functional groups. Also demonstrated is the applicability of the strategy through several synthetic transformations of the products, as well as the syntheses of the natural product iso-moracin and the drug (E)-metanicotine.     

Alkoxide-induced reactions of N-substituted saccharins. Synthesis of 1,2-benzothiazocine 1,1-dioxide and 2,3-dihydropyrrolo[1,2-b]-[1,2]benzisothiazole 5,5-dioxide derivatives

The reactions of saccharin derivatives 1 with sodium alkoxides were studied. Under mild conditions, compounds 1a-f gave the corresponding open sulfonamides 5a-f . Under drastic conditions, β-(saccharin-2)propionic acid derivatives 1a,b reacted with sodium ethoxide affording saccharin and β-ethoxypropionic acid derivatives 4a,b . γ-(Saccharin-2)butyric acid derivatives 1c,d and γ-(saccharin-2)-butyrophenone 1f reacted with sodium t-butoxide in dimethyl sulfoxide affording 5-substituted 6-hydroxy-3,4-dihydro-2H-1,2-benzothiazocine 1,1-dioxides 9 . From mother liquors, 1-substituted 2,3-dihydro-pyrrolo[1,2-b][1,2]benzisothiazole 5,5-dioxides 10 were isolated several hours later, though not detected immediately after completing the reaction. When the reactions were carried out in t-butyl alcohol, the yields of 9 diminished and those of 10 increased with product ratio inversion. Different experimental observations on the possible pathway generating 9 and 10 are discussed.     

Polymeric formamides as liquid–liquid phase transfer catalysts

Polymeric formamides were prepared by free radical polymerization of N-methyl-N-vinyl-formamide or N-methyl-N-(4-vinylbenzyl)formamide, and copolymerization of these monomers with styrene. These soluble polymers serve as phase transfer catalysts for several reactions under liquid–liquid biphase conditions. The catalytic activity of copolymers containing styrene unit is affected remarkably by composition, and there are maxima at certain composition in both polymers. However, copolymers with an acrylonitrile co-unit scarcely exhibit catalytic activity. Furthermore, it was found that these polymers can extract all alkali metal ions employed here, and that the extraction ability increases with increasing the density of active sites. From these results, it is demonstrated that catalytic activity strongly depends on both cation extraction ability of polymers and lipophilicity around the active sites in the polymer.     

Morphology and glass transition behavior of polycarbonate–phenoxy system: Effects of trans-reactions in domain interface regions

Effects of trans reactions on the morphology, glass transition, and phase behavior in a classical blend system of a poly(hydroxyl ether bisphenol-A) (phenoxy) with bisphenol-A polycarbonate (PC) were investigated by differential scanning calorimetry (DSC) and optical microscopy. Although two T_gs were observed in the as-prepared PC/phenoxy blends, an apparently single, but broadened, T_g was found in the blends after heating at high temperatures, typically 200–250°C for short times. The optical microscopy results indicated that same scales of heterogeneity did exist in post-heated PC/phenoxy blends as well as unheated blends. Explanations were provided. After heating-induced interchange reactions ( OH and carbonate), randomly linked polymer chains might form at the numerous interfaces of the mutually occluded/included micro-domains. The majority of the chains in the micro-domains are forced to relax in coordinated motion modes after heating, thus showing a single T_g. A mechanism of trans reactions in interfacial regions was briefly discussed in supplement to earlier reports in the literature. © 1997 John Wiley & Sons, Inc.     

液相色谱-质谱法对电子电气产品塑料部件中有机锡的测定

建立了液相色谱-质谱法同时测定电子电气产品塑料部件中3种有机锡的方法.样品经四氢呋喃溶解,并经甲醇沉淀杂质后,用液相色谱-质谱仪进行测定和确证.色谱柱为ZORBAX 300-SCX柱(250 mm×4.6 mm×5 μm i.d.),流动相为体积比80 : 20的甲醇-20 mmol/L醋酸铵(含0.01%冰乙酸),等度洗脱,流速为1.0 mL/min,选择离子监测模式.三丁基锡、三苯基锡、三辛基锡的线性范围分别为0.1 ～10.0、0.1 ～10.0、0.05 ～5.0 mg/L(相关系数r~2≥0.999 2),方法定量下限(LOQ)依次为0.005%、0.005%、0.0025%;平均加标回收率为80% ～100%,相对标准偏差为1.6% ～11.5%(n=6).     

Dealkenylative Alkenylation: Formal σ‐Bond Metathesis of Olefins

The dealkenylative alkenylation of alkene C(sp³)?C(sp²) bonds has been an unexplored area for C?C bond formation. Herein 64 examples of β‐alkylated styrene derivatives, synthesized through the reactions of readily accessible feedstock olefins with β‐nitrostyrenes by ozone/Fe^II‐mediated radical substitutions, are reported. These reactions proceed with good efficiencies and high stereoselectivities under mild reaction conditions and tolerate an array of functional groups. Also demonstrated is the applicability of the strategy through several synthetic transformations of the products, as well as the syntheses of the natural product iso‐moracin and the drug (E)‐metanicotine.     

Allylation Reactions of Aldehydes with Allylboronates in Aqueous Media: Unique Reactivity and Selectivity that are Only Observed in the Presence of Water

Zn(OH)₂‐catalyzed allylation reactions of aldehydes with allylboronates in aqueous media have been developed. In contrast to conventional allylboration reactions of aldehydes in organic solvents, the α‐addition products were obtained exclusively. A catalytic cycle in which the allylzinc species was generated through a B‐to‐Zn exchange process is proposed and kinetic studies were performed. The key intermediate, an allylzinc species, was detected by HRMS (ESI) analysis and by online continuous MS (ESI) analysis. This analysis revealed that, in aqueous media, the allylzinc species competitively reacted with the aldehydes and water. An investigation of the reactivity and selectivity of the allylzinc species by using several typical allylboronates ( 6a , 6b , 6c , 6d ) clarified several important roles of water in this allylation reaction. The allylation reactions of aldehydes with allylboronic acid 2,2‐dimethyl‐1,3‐propanediol esters proceeded smoothly in the presence of catalytic amounts of Zn(OH)₂ and achiral ligand 4d in aqueous media to afford the corresponding syn‐adducts in high yields with high diastereoselectivities. In all cases, the α‐addition products were obtained and a wide substrate scope was tolerated. Furthermore, this reaction was applied to asymmetric catalysis by using chiral ligand 9 . Based on the X‐ray structure of the Zn‐ 9 complex, several nonsymmetrical chiral ligands were also found to be effective. This reaction was further applied to catalytic asymmetric alkylallylation, chloroallylation, and alkoxyallylation processes and the synthetic utility of these reactions has been demonstrated.     

Tables of gamma rays emitted by radionuclides produced through photonuclear reactions

The tables have been prepared as an auxiliary for the interpretation of results in photoactivation analysis. They include data concerning the disintegration of radionuclides produced by (γ, n) reactions on all stable isotopes with a relative abundance greater than 1% and by (γ, p) reactions on elements withZ≤39. The γ-rays are listed in ascending order of the energies; half-lives, intensities and other useful informations are also included.     

A Redox-Active Microporous Organosiloxane Containing a Stable Neutral Radical,Trioxotriangulene

A new silyl-substituted trioxotriangulene ( TOT ) neutral radical and corresponding porous organosiloxanes (POSs) were synthesized. The neutral radical exhibited a peculiarly high stability and formed a diamagnetic π-dimer characteristic to TOT neutral radicals stabilized by the strong multiple SOMO-SOMO interaction in both solution and solid states. POSs including TOT units within the organosiloxane-wall were prepared by polycondensation of the silyl groups and formed microporous structures with ∼1 nm-size diameters. Redox ability of TOT units in the POS was demonstrated by the treatment of oxidant/reductant in heterogeneous suspension condition, where the TOT units were reversibly converted between reduced and neutral radical species. Furthermore, the solid-state electrochemical measurements of the POS revealed the reversible multi-stage redox ability of TOT units involving polyanionic species within the organosiloxane-wall.