Catalytic Borylation of SCF3‐Functionalized Arenes by Rhodium(I) Boryl Complexes: Regioselective C?H Activation at the ortho‐Position

An unprecedented reaction pathway for the borylation of SCF₃‐containing arenes using [Rh(Bpin)(PEt₃)₃] (pin=pinacolato) is reported. Catalytic processes were developed and the functionalizations proceed under mild reaction conditions. The C H activations occur with a unique regioselectivity for the position ortho to the SCF₃ group, which apparently serves as directing group. Borylated SCF₃ compounds can serve as versatile building blocks.     

Catalytic Borylation of SCF3‐Functionalized Arenes by Rhodium(I) Boryl Complexes: Regioselective CH Activation at the ortho‐Position

An unprecedented reaction pathway for the borylation of SCF₃‐containing arenes using [Rh(Bpin)(PEt₃)₃] (pin=pinacolato) is reported. Catalytic processes were developed and the functionalizations proceed under mild reaction conditions. The C? H activations occur with a unique regioselectivity for the position ortho to the SCF₃ group, which apparently serves as directing group. Borylated SCF₃ compounds can serve as versatile building blocks.     

Palladium-catalyzed intramolecular α-arylation of aliphatic ketone, formyl, and nitro groups

Intramolecular arylation of properly designed substrates bearing a ketone, formyl, or nitro terminating group was achieved by use of a PdCl₂(Ph₃P)₂-Cs₂CO₃ reaction system to form a variety of carbocyclic compounds. Arylation in ketone compounds afforded benzene-annulated bridged or spirocycloalkanone derivatives, depending on the structure of the cyclization precursors. Arylation in formyl compounds occurred at the α-position (α-arylation) or at the carbonyl carbon (carbonyl-arylation) depending on the structure of the cyclization precursors and on the reaction solvent. An α-arylated secondary nitro group was partially transformed to ketone in the manner of the Nef reaction, whereas a tertiary nitro group was partially eliminated to afford a styrene-type olefin.     

Hydrosilanes are not always a reducing reagent: a ruthenium-catalyzed introduction of primary alkyl groups to electron-rich aromatic rings using esters as a source of the alkyl groups

A triruthenium cluster, (μ₃, η², η³, η⁵-acenaphthylene)Ru₃(CO)₇ effectively catalyzes primary-alkylation reaction of electron-rich aromatic rings using a combination of hydrosilane and ester as a source of the primary-alkyl group. The reaction involves electrophilic substitution of arenes by carbocationic species stabilized by a neighboring alkoxy or siloxy group generated during the reduction of esters giving alkylated arenes after reductive removal of the alkoxy or siloxy group at the benzylic position.     

Recherches sur la formation et la transformation des esters LXXV[1]. Amines,amino-alcools et aminoalcoyl-monoesters des acides orthophosphorique et sulfurique: thiocarbamylation par l'isothiocyanate d'o-méthoxycarbonylphényle sans ou avec cyclisation intramoléculaire

o-Methoxycarbonyl-phenylisothiocyanate V and primary alkylamines (R″? NH₂) reacted in the appropriate medium yield the corresponding 2-mercapto-3-alkyl-3, 4-dihydro-quinazolinone-4 derivatives VI (the ? NH₂ group is thiocarbamoylated by the ? N?C?S group and then acylated in an intramolecular reaction by the ? COOCH₃ group with elimination of CH₃OH).     

New procedure for nucleophilic sulfonation of aromatic nitro compounds: Destructive oxidation of S-arylthioglycolic acids esters

A new reaction was discovered: oxidative destruction of sulfides of ArSCH₂CO₂Me type to sulfonic acids ArSO₃H effected by 70% HNO₃. This reaction was used to introduce an SO₃H group instead of aromatic nitro group activated only by meta-substituents: At treating with HSCH₂CO₂Me + K₂CO₃ the NO₂ group was substituted to form ArSCH₂CO₂Me with subsequent transformation into ArSO₃H. p-Fluoronitrobenzene behaved similarly (with replacement of the fluorine).     

An Efficient Synthesis of 2-CF3-3-Benzylindoles

The reaction of α-CF₃-β-(2-nitroaryl) enamines with benzaldehydes afforded effectively α,β-diaryl-CF₃-enones having nitro group. Subsequent reduction of nitro group by NH₄HCO₂-Pd/C system initiated intramolecular cyclization to give 2-CF₃-3-benzylindoles. Target products can be prepared in up to quantitative yields. Broad synthetic scope of the reaction was shown. Probable mechanism of indole formation is proposed.     

Trimeric cluster of lithium amidoborane—the smallest unit for the modeling of hydrogen release mechanism

A detailed first‐principle DFT M06/6‐311++G(d.p) study of dehydrogenation mechanism of trimeric cluster of lithium amidoborane is presented. The first step of the reaction is association of two LiNH₂BH₃ molecules in the cluster. The dominant feature of the subsequent reaction pathway is activation of H atom of BH₃ group by three Li atoms with formation of unique Li₃H moiety. This Li₃H moiety is destroyed prior to dehydrogenation in favor of formation of a triangular Li₂H moiety, which interacts with protic H atom of NH₂ group. As a result of this interaction, Li₂H₂ moiety is produced. It features N^?? H⁺? H^? group suited near the middle plane between two Li⁺ in the transition state that leads to H₂ release. The transition states of association and hydrogen release steps are similar in energy. It is concluded that the trimer, (LiNH₂BH₃)₃, is the smallest cluster that captures the essence of the hydrogen release reaction. © 2016 Wiley Periodicals, Inc.     

Shape Controlling Synthesis — Formation of Fe3Si by the Reaction of Iron with Silicon Tetrachloride and Crystal Structure Refinement

Pure Fe₃Si is formed by the reaction of an iron‐wire with SiCl₄‐vapor at a reaction temperature of 1000 °C and a SiCl₄‐pressure of 2 bar. Remarkable is the fact that the outer shape of the used iron wire has not been changed during the reaction. The crystal structure of Fe₃Si was determined using single crystal methods. Fe₃Si crystallizes in the space group Fm3m. The lattice parameters depend on the composition.     

Synthesis of Aryl 3,5-Dinitrophenyl Sulfones and Sulfoxides. Transformations of 3,5-Dinitrodiphenyl Sulfone in Reactions with O- and S-Nucleophiles

1-Arylthio-3,5-dinitrobenzenes are selectively oxidized to the corresponding sulfones and sulfoxides by the action of hydrogen peroxide. Reactions of 3,5-dinitrodiphenyl sulfone with O- and S-centered nucleophiles (RXH, X = O, S) in dipolar aprotic solvents in the presence of K₂CO₃ result in replacement of the nitro group by the RX fragment; the reaction with methanol occurs in aqueous medium in the presence of NaHCO₃. Substitution of the nitro group in 3,5-dinitrodiphenyl sulfone by phenylthio group, followed by oxidation of the sulfur atom to SO₂ and further replacement of the remaining nitro group yields 1,3,5-tris(phenylsulfonyl)benzene. The phenylsulfonyl group in the latter is replaced by phenylthio group by reaction with PhSH in the presence of K₂CO₃. Mononitrosulfones obtained by nucleophilic substitution in the title compound can be reduced to the corresponding anilines.     

Stereospecific Oxycyanation of Alkenes with Sulfonyl Cyanide

Oxycyanation of alkenes would allow the direct construction of useful β-hydroxy nitrile scaffolds. However, only limited examples of such reactions have been reported, and some problems including limited substrate scope and the lack of diastereocontrol in the case of the oxycyanation of internal alkenes have arisen. We herein report on the intermolecular oxycyanation of alkenes using p-toluenesulfonyl cyanide (TsCN) in the presence of tris(pentafluorophenyl)borane (B(C₆F₅)₃) as a catalyst, affording products that contain a sulfinyloxy group and a cyano group at the vicinal position. The reaction features a stereospecific syn-addition. The reaction also shows a broad substrate scope with good functional group tolerance. Mechanistic investigations by experimental studies and density functional theory (DFT) calculations revealed that the reaction proceeds via an unprecedented stereospecific mechanism through the electrophilic cyanation of alkenes, in which B(C₆F₅)₃ efficiently activates TsCN through the coordination of the cyano group to the boron center.     

Reactions of Propargyl Compounds Containing a Cyclobutyl Group Induced by a Ruthenium Complex

Reactions of [Ru]Cl ([Ru]={Cp(PPh₃)₂Ru}; Cp=cyclopentadienyl) with three alkynyl compounds, 1 , 5 , and 8 , each containing a cyclobutyl group, are explored. For 1 , the reaction gives the vinylidene complex 2 , with a cyclobutylidene group, through dehydration at C_δH and C_γOH. With an additional methylene group, compound 5 reacts with [Ru]Cl to afford the cyclic oxacarbene complex 6 . The reaction proceeds via a vinylidene intermediate followed by an intramolecular cyclization reaction through nucleophilic addition of the hydroxy group onto C_α of the vinylidene ligand. Deprotonation of 2 with NaOMe produces the acetylide complex 3 and alkylations of 3 by allyl iodide, methyl iodide, and ethyl iodoacetate generate 4 a – c , respectively, each with a stable cyclobutyl group. Dehydration of 1 is catalyzed by the cationic ruthenium acetonitrile complex at 70 °C to form the 1,3‐enyne 7 . The epoxidation reaction of the double bond of 7 yields oxirane 8 . Ring expansion of the cyclobutyl group of 8 is readily induced by the acidic salt NH₄PF₆ to afford the 2‐ethynyl‐substituted cyclopentanone 9 . The same ring expansion is also seen in the reaction of [Ru]Cl with 8 in CH₂Cl₂, affording the vinylidene complex 10 , which can also be obtained from 9 and [Ru]Cl. However, in MeOH, the same reaction of [Ru]Cl with 8 affords the bicyclic oxacarbene complex 12 a through an additional cyclization reaction. Transformation of 10 into 12 a is readily achieved in MeOH/HBF₄, but, in MeOH alone, acetylide complex 11 is produced from 10 . In the absence of MeOH, cyclization of 10 , induced by HBF₄, is followed by fluorination to afford complex 13 . Crystal structures of 6 and 12 a ′ were determined by single‐crystal diffraction analysis.     

Replacement of an oxygen atom by chlorine atoms in the reaction of pentafluorobenzaldehyde with CCl3-substituted compounds in the presence of AlCl3

The interaction of pentafluorobenzaldehyde with RCCl₃ (R = Cl, Ph, C₆F₅) in the presence of threefold molar excess of AlCl₃ proceeds with replacing the oxygen atom of the aldehyde group by two chlorine atoms from the CCl₃ group and results in the formation of pentafluorobenzylidene chloride. The electrophilic mechanism of the reaction is proposed.     

Grignard Reaction as a Result of Tunneling of the Triplet Branch of the Reaction Through a Singlet Barrier

Quantum-chemical calculations were carried out to study the mechanism of the Grignard reaction Mg + CH₃F. The reaction between Mg, CH₃F gives rise to a triplet complex which has a lower energythan the corresponding singlet complex at MgFCH₃ angles ranging from 60 to 139°. The transition from thesinglet branch of the reaction to the nonequilibrium triplet branch results in decomposition of CH₃F with formation of various final products. A linear Grignard reagent CH₃-Mg-F is formed by simultaneous homolytic CH₃-F dissociation and ionic covalent interaction of the methyl group and the fluorine atom with the magnesium cation arising in the course of the reaction. Normal mode frequencies for the Mg + CH₃F complex at various MgFCH₃ are were calculated. The calculation results nicely agree with experimental data.     

Palladium(II)‐Catalyzed Enantioselective Aminotrifluoromethoxylation of Unactivated Alkenes using CsOCF3 as a Trifluoromethoxide Source

Asymmetric Pd^II‐catalyzed intramolecular aminotrifluoromethoxylation of unactivated alkenes using readily accessible and stable CsOCF₃ as a trifluoromethoxide source has been developed, which affords a wide variety of enantiomerically enriched β‐substituted OCF₃‐containing piperidines in good yields. Introducing a sterically bulky group into pyridine‐oxazoline (Pyox) ligands is crucial to increasing both reactivity and enantioselectivity for the reaction. Additionally, the reaction features good functional group compatibility and mild reaction conditions.     

KINETIC STUDIES OF LEWIS BASE ADDITION TO CpFe(CO)(η3-CH2C6H4-p-X); X = OMe,Me, H,F, Cl,Br

Abstract

Kinetic studies illuminate details of the reaction of photoproduced CpFe(CO)(η³-CH₂C₆H₅) with two electron Lewis bases. Rate constants of 151(10)M^?1s^?1 for CO back reaction and between 440 and 3200 M^?1s^?1 for reaction with various phosphine nucleophiles were recorded. Linear free energy analysis quantifies the stereoelectronic effect of the nucleophile. Variation of the para-substituent on the benzyl group demonstrates that an electron rich benzyl group impedes reaction. The effect of ancillary ligands was seen by substitution of C₅Me₅ for C₅H₅. The large, electron rich C₅Me₅ speeds up CO substitution but slows down PPh₃ substitution. Mechanistic clues were obtained from Eyring plots for reaction of CpFe(CO)(η³-CH₂C₆H₅) with 4 different phosphines. Examination of the measured enthalpy and entropy barriers suggests a stepwise reaction mechanism.     

A new reaction of fluorodinitromethyl group

A general reaction of the transformation of the fluorodinitromethyl group into the fluoronitromethyl group by denitration upon treatment with Na₂SO₃ or KI in aqueous formaldehyde was found. A preparative method for synthesizing fluoronitroalcohols was developed on the basis of this reaction.     

Direct Trifluoromethylthiolation of Unactivated C(sp3)?H Using Silver(I) Trifluoromethanethiolate and Potassium Persulfate

A practical and efficient method for the direct trifluoromethylthiolation of unactivated C(sp³) H bonds by AgSCF₃/K₂S₂O₈ under mild conditions is described. The reaction has a good functional‐group tolerance and good selectivity. Initial mechanistic investigations indicate that the reaction may involve a radical process in which K₂S₂O₈ plays key roles in both the activation of the C(sp³) H bond and the oxidation of AgSCF₃.     

Direct Trifluoromethylthiolation of Unactivated C(sp3)H Using Silver(I) Trifluoromethanethiolate and Potassium Persulfate

A practical and efficient method for the direct trifluoromethylthiolation of unactivated C(sp³)? H bonds by AgSCF₃/K₂S₂O₈ under mild conditions is described. The reaction has a good functional‐group tolerance and good selectivity. Initial mechanistic investigations indicate that the reaction may involve a radical process in which K₂S₂O₈ plays key roles in both the activation of the C(sp³)? H bond and the oxidation of AgSCF₃.     

Ferric Acetylacetonate Catalyst on the Urethane Reaction of Phenyl Isocyanate and 1,2-Propyleneglycol: A Study of Kinetics,Thermodynamics, and Mechanism with In Situ FT-IR Spectroscopy

The urethane reaction of phenyl isocyanate and 1,2-propylene glycol was investigated with ferric acetylacetonate (Fe(acac)₃) as catalyst. The effect of the catalytic properties of Fe(acac)₃ on the formation of the urethane bond was evaluated with in situ FT-IR. The influence of the Fe(acac)₃ concentration as well as the reaction temperature is discussed. It was observed that there was a turning point in the reaction rate when the temperature decreases, which remained unchanged with variation in Fe(acac)₃ concentration. Arrhenius and Eyring parameters of the primary hydroxyl group were determined for the catalyzed reaction. The low-temperature and high-temperature values are surprisingly different. A reasonable reaction mechanism is proposed and the possible active species are discussed, followed by a kinetics and thermodynamics discussion.