Borylene transfer from an iron bis(borylene) complex: synthesis of 1,4-diboracyclohexadiene and 1,4-dibora-1,3-butadiene complexes

Diene to be made: By tuning the size of acetylenic substituents, 1,4-diboracyclohexadiene and unprecedented 1,4-dibora-1,3-butadiene complexes were generated in a controlled manner by borylene transfer from an iron bis(borylene) complex to alkynes (see scheme).     

Hydridoborylene Complexes and Di‐, Tri‐, and Tetranuclear Borido Complexes with Hydride Ligands

Mono‐ and dinuclear hydridoborylene complexes were prepared by intermetallic borylene transfer from Group VI borylene or metalloborylene reagents. The hydride and borylene ligands were found to interact with each other significantly, although the boron ligand retains much of its former borylene character. Zero‐valent platinum fragments were successively added to the dinuclear hydridoborylene complexes, resulting in tri‐ and tetranuclear borido complexes, in which the B? H interaction has been lost, and the hydride ligands now bridge two metal centers. The complexes were studied spectroscopically, crystallographically, and by DFT methods, and the unusual bonding situation in the M? B? H triangles of hydridoborylene complexes were evaluated.     

Ge=B π‐Bonding: Synthesis and Reversible [2+2] Cycloaddition of Germaborenes

Phosphine‐stabilized germaborenes featuring an unprecedented Ge=B double bond with short B???Ge contacts of 1.886(2) ( 4 ) and 1.895(3) Å ( 5 ) were synthesized starting from an intramolecular germylene–phosphine Lewis pair ( 1 ). After oxidative addition of boron trihalides BX₃ (X=Cl, Br), the addition products were reduced with magnesium and catalytic amounts of anthracene to give the borylene derivatives in yields of 78 % ( 4 ) and 57 % ( 5 ). These halide‐substituted germaborenes were characterized by single‐crystal structure analysis, and the electronic structures were studied by quantum‐chemical calculations. According to an NBO NRT analysis, the dominating Lewis structure contains a Ge=B double bond. The germaborenes undergo a reversible, photochemically initiated [2+2] cycloaddition with the phenyl moiety of a terphenyl substituent at room temperature, forming a complex heterocyclic structure with Ge^IV in a strongly distorted coordination environment.     

Borido complexes via intermetallic metalloborylene transfer

Intermetallic borylene transfer has been applied to synthesise new borido complexes. Starting from [{(η(5)-C(5)Me(5))Fe(CO)(2))}(μ-B){Cr(CO)(5)}] (1) the borylene moiety has been transferred successfully to different transition metal fragments. In the manner described, two new compounds have been fully characterised in solution and by X-ray crystallography.     

6-羟基-5,12-萘并萘醌及其CH3, C6H5取代衍生物的光致变色理论研究

用密度泛函理论的B3LYP/6-31G方法和从头算的CIS/6-31G方法分别研究了6-羟基-5,12-萘并萘醌及其CH₃, C₆H₅取代衍生物基态和激发态的异构化反应，.对反应势能面的研究发现, 在光异构化反应中化合物M21和M21、M31的基态和激发态虽然都可以构成四能级反应过程, 但由于M21异构化过程的活化能较高, 使其所构成的四能级反应难以进行, 这就从理论上解释了迁移基团为甲基的M21变色性能低于迁移基团为苯基的M31的实验结果. 此外用TD/B3LYP方法在溶剂存在下计算了上述化合物的紫外吸收光谱和荧光发射光谱, 计算所得到的光谱数据与实验值基本一致, 与光异构化反应的光激发条件相符合.     

Oxygen transfer reactions. 4. Reaction of high valent oxoruthenium compounds with sulfides

The oxidation of methoxy substituted benzyl phenyl sulfides can be used to distinguish between oxidants that react by single electron transfer (followed by oxygen rebound) and those which react by direct oxygen atom transfer in a two-electron process. Transfer of a single electron results in the formation of an intermediate radical cation, which can undergo C-S bond cleavage and deprotonation reactions leading to the formation of methoxy substituted benzyl derivatives, methoxy substituted benzaldehydes, and diphenyl disulfide. The oxidation of 4-methoxybenzyl phenyl sulfide and 3,4,5-trimethoxybenzyl phenyl sulfide by oxidants known to participate in single electron transfers (Ce(4+), Mn(3+), and Cr(6+)) results in the formation of the corresponding benzaldehydes, benzyl alcohols, benzyl acetates, and benzyl nitrates in variable yields. However, the only products obtained from the oxidation of the same compounds with RuO(4), RuO(4-), and RuO(4)(2-) are sulfoxides and sulfones. Therefore, it is concluded that the oxidation of sulfides by oxoruthenium compounds likely proceeds by a concerted mechanism.     

Mechanism of (Salen)manganese(III)‐Catalyzed Oxidation of Aryl Phenyl Sulfides with Sodium Hypochlorite

The oxidation of 4‐substituted phenyl phenyl sulfides was carried out with several oxo(salen)manganese(V) complexes in MeCN/H₂O 9 : 1. The kinetic data show that the reaction is first‐order each in the oxidant and sulfide. Electron‐attracting substituents in the sulfides and electron‐releasing substituents in salen of the oxo(salen)manganese(V) complexes reduce the rate of oxidation. A Hammett analysis of the rate constants for the oxidation of 4‐substituted phenyl phenyl sulfides gives a negative ρ value (ρ=?2.16) indicating an electron‐deficient transition state. The log k₂ values observed in the oxidation of each 4‐substituted phenyl phenyl sulfide by substituted oxo(salen)manganese(V) complexes also correlate with Hammett σ constants, giving a positive ρ value. The substituent‐, acid‐, and solvent‐effect studies indicate direct O‐atom transfer from the oxidant to the substrate in the rate‐determining step.     

Asymmetric conjugate additions of α-substituted-α-cyanoacetates to acetylenic ketones by chiral phase transfer catalysis

Asymmetric conjugate addition of α-substituted-α-cyanoacetates to acetylenic ketones has been achieved with high enantioselectivity and moderate E/Z selectivity under the influence of our recently designed, binaphthyl-modified 3,5-bis[3,5-bis(trifluoromethyl)phenyl]phenyl substituted phase transfer catalyst.     

Synthesis and Structure of Heterodinuclear Rhodium and Iridium Borylene Complexes

Herein we report on the synthesis and structural characterization of a representative range of novel heterodinuclear bridging rhodium and iridium borylene complexes. The iridium borylene complexes feature an unusual coordination mode of the borylene ligand. Furthermore, the first instance of a heterodinuclear‐bridged borylene compound containing a chromium atom in the three‐membered ring is reported.     

Competitive proton and hydride transfer reactions via ion‐neutral complexes: fragmentation of deprotonated benzyl N‐phenylcarbamates in mass spectrometry

The gas‐phase chemistry of deprotonated benzyl N‐phenylcarbamates was investigated by electrospray ionization tandem mass spectrometry. Characteristic losses of a substituted phenylcarbinol and a benzaldehyde from the precursor ion were proposed to be derived from an ion‐neutral complex (INC)‐mediated competitive proton and hydride transfer reactions. The intermediacy of the INC consisting of a substituted benzyloxy anion and a phenyl isocyanate was supported by both ortho‐site‐blocking experiments and density functional theory calculations. Within the INC, the benzyloxy anion played the role of either a proton abstractor or a hydride donor toward its neutral counterpart. Relative abundances of the product ions were influenced by the nature of the substituents. Electron‐withdrawing groups at the N‐phenyl ring favored the hydrogen transfer process (including proton and hydride transfer), whereas electron‐donating groups favored direct decomposition to generate the benzyloxy anion (or substituted benzyloxy anion). By contrast, electron‐withdrawing and electron‐donating substitutions at the O‐benzyl ring exhibited opposite effects. Copyright © 2015 John Wiley & Sons, Ltd.     

Photochromic reactions of 6-hydroxy-5,12-naphthacenequinone and its derivatives bearing methyl or phenyl groups

Photoisomerizations of 6-hydroxy-5,12-naphthacenequinone and its derivatives bearing methyl and phenyl group were theoretically investigated with density functional theory and ab initio CIS method at the B3LYP 6-31G basis set, respectively. The obtained potential energy curves revealed that a four-state cycle existed in the ground and excited states. It was also found that the activation energy for the methyl transfer was higher compared to that for the phenyl transfer, and this was consistent with the experimental results that the photoisomerization of the phenyl substituted derivative was more rapid than that of the methyl substituted derivatives. Further hybrid time-dependent density functional theory (TD-DFT) was used to investigate the absorption and fluorescence spectra of these compounds under solvent effect condition. The calculated values were in agreement with the experimental results and the excitation condition of photochromic reactions. __________ Translated from Acta Chimica Sinica, 2007, 65(24): 2821–2826     

1,4—双（苯基乙炔基）苯及其双取代苯基衍生物的研究

合成了1,4-双(苯基乙炔基)苯及其双取代苯基衍生物。测定了它们的荧光量子产率、激光转换效率、红外光谱、拉曼光谱,指派了主要官能团的特征频率,讨论了化合物结构和取代基效应。     

Silane. XII. Alkalische Solvolyse von substituierten Benzylsilanen

Alcaline solvolysis of substituted phenyl and benzyl silanes listed in “Inhaltsübersicht” is compared. The inductive transfer coefficient of the CH₂ group is fixed.     

Preparation of 2‐Arylethynylselanylacetonitriles from 4‐Aryl‐1,2,3‐selenadiazoles

Base decomposition of 4‐(substituted phenyl)‐1,2,3‐selenadiazoles at room temperature resulted in 2‐(substituted phenyl)‐ethynylselenolate anions, which were immediately reacted with bromoacetonitrile to give a series of 2‐(substituted phenyl)ethynylselanylacetonitriles.     

Synthesis and antimalarial effects of N,N-dialkyl-6-(substituted phenyl)-1,2,4,5-tetrazin-3-amines

The synthesis of a series of N,N-dialkyl-6-(substituted phenyl)-1,2,4,5-tetrazin-3-amines (IV) by two routes is described. The first route (Scheme I) involved the oxidative cyclization of formazans (II) to 3-bromo-6-(substituted phenyl)-1,2,4,5-tetrazines (III), followed by treatment with amines. The second (Scheme II) utilized the treatment of 3-(methylthio)-6-(substituted phenyl)-1,2,4,5-tetrazines (VII) with amines to provide the desired products. The intermediate 3-(methylthio)-6-(substituted phenyl)-1,2,4,5-tetrazines (VII) were obtained by thiobenzoylation of hydrazinecarbohydrazonothioic acid methyl ester with [[(substituted phenyl)thioxomethyl]thio]-acetic acids (V) to afford the 1,2-dihydro-3-(methylthio)-6-(substituted phenyl)-1,2,4,5-tetrazines (VI). Oxidation with bromine in acetic acid provided the desired intermediates. The target 6-(substituted phenyl)-1,2,4,5-tetrazin-3-amines (IV) displayed modest antimalarial activity.     

4,5‐Di­hydro‐3‐methyl‐5‐(4‐methyl­phenyl)‐1H‐pyrazole‐1‐carbox­amide

The reaction between 4‐(4‐methyl­phenyl)­but‐3‐en‐2‐one and amino­guanidine produced an unexpected product of formula C₁₂H₁₅N₃O, consisting of a carbox­amide moiety joined to a substituted pyrazoline ring at one of the N atoms. The pyrazoline ring adopts a flat‐envelope conformation and the substituted phenyl ring is oriented almost perpendicular to the heterocycle. The carbonyl O atom has partial anionic character as a result of the transfer of π density from the two adjacent sp² N atoms and is involved in an intermolecular hydrogen bond with the amide group.     

Effects of Phenyl‐ and Methyl‐Substituents on p‐Phenylenediamine,an Electrochemical and Spectral Study

Two series of substituted p‐phenylenediamines have been studied for their electronic effects on redox potential and spectral properties. p‐Phenylenediamines and N,N,N′,N”‐tetramethyl‐p‐phenylenediamine substituted with different numbers of phenyl groups have been synthesized and their cyclic voltammograms have been obtained. The correlation between the substituent number and the redox potential appears linear. The slope reflects the additive effect of electron‐donating methyl and electron‐withdrawing phenyl groups. The absorption spectra of the cation radicals indicate that phenyl‐substituted ones have broad intervalence‐charge transfer bands. The p‐phenylenediamines exhibit different properties from triphenylamines in that the oxidized forms are more stable in CH₃CN then those in CH₂Cl₂. Some of the cation radicals or dications could undergo follow‐up chemical reactions and form products that are more easily oxidized.     

Enantioselective Synthesis of Quaternary Carbon Stereocenters: Addition of 3‐Substituted Oxindoles to Vinyl Sulfone Catalyzed by Pentanidiums

A pentanidium‐catalyzed highly enantioselective conjugate addition of 3‐alkyloxindoles to phenyl vinyl sulfone has been demonstrated. This approach allows the construction of 3,3‐dialkyl‐substituted oxindole frameworks with high yield and excellent enantioselectivity (up to 99 %) under simple phase‐transfer conditions. A variety of oxindoles bearing all‐carbon quaternary stereogenic centers were obtained in the presence of 0.25 mol % pentanidium. Meanwhile, practicality was illustrated by a gram‐scale asymmetric synthesis of two 3,3‐dialkyl‐substituted oxindoles. The resulting adduct can be smoothly transformed to the natural product analogue in a short synthetic route.     

A Vinyl Cyclopropane Ring Expansion and Iridium‐Catalyzed Hydrogen Borrowing Cascade

A vinyl cyclopropane rearrangement embedded in an iridium‐catalyzed hydrogen borrowing reaction enabled the formation of substituted stereo‐defined cyclopentanes from Ph* methyl ketone and cyclopropyl alcohols. Mechanistic studies provide evidence for the ring‐expansion reaction being the result of a cascade based on oxidation of the cyclopropyl alcohols, followed by aldol condensation with the pentamethyl phenyl‐substituted ketone to form an enone containing the vinyl cyclopropane. Subsequent single electron transfer (SET) to this system initiates a rearrangement, and the catalytic cycle is completed by reduction of the new enone. This process allows for the efficient formation of diversely substituted cyclopentanes as well as the construction of complex bicyclic carbon skeletons containing up to four contiguous stereocentres, all with high diastereoselectivity.     

Substituent and Solvent Effects on the Excited State Deactivation Channels in Anils and Boranils

Differently substituted anils (Schiff bases) and their boranil counterparts lacking the proton‐transfer functionality have been studied using stationary and femtosecond time‐resolved absorption, fluorescence, and IR techniques, combined with quantum mechanical modelling. Dual fluorescence observed in anils was attributed to excited state intramolecular proton transfer. The rate of this process varies upon changing solvent polarity. In the nitro‐substituted anil, proton translocation is accompanied by intramolecular electron transfer coupled with twisting of the nitrophenyl group. The same type of structure is responsible for the emission of the corresponding boranil. A general model was proposed to explain different photophysical responses to different substitution patterns in anils and boranils. It is based on the analysis of changes in the lengths of CN and CC bonds linking the phenyl moieties. The model allows predicting the contributions of different channels that involve torsional dynamics to excited state depopulation.