Enantiospecific sp2–sp3 Coupling of ortho‐ and para‐Phenols with Secondary and Tertiary Boronic Esters

The coupling of ortho ‐ and para ‐phenols with secondary and tertiary boronic esters has been explored. In the case of para ‐substituted phenols, after reaction of a dilithio phenolate species with a boronic ester, treatment with Ph₃BiF₂ or Martin's sulfurane gave the coupled product with complete enantiospecificity. The methodology was applied to the synthesis of the broad spectrum antibacterial natural product (−)‐4‐(1,5‐dimethylhex‐4‐enyl)‐2‐methyl phenol. For ortho ‐substituted phenols, initial incorporation of a benzotriazole on the phenol oxygen atom was required. Subsequent ortho ‐lithiation and borylation gave the coupled product, again with complete stereospecificity.     

Alkylamination of pteridines by primary alkylamines - potassium permanganate

Reaction of 7-phenyl, 7-p-methoxyphenyl, 7-t-butyl- and 6,7-diphenylpteridine with ethylamine and t-butylamine in the presence of potassium permanganate leads to the introduction of the ethylamino or t-butylamino group at C-4 in the above-mentioned pteridines. In the reaction of ethylamine/potassium permanganate besides the 4-(ethylamino)pteridine derivatives 2-amino-3-formytpyrazines are obtained as side-products. In the reaction with t-butylamine/potassium permanganate the corresponding pteridin-4-ones are obtained as by-products. The ¹H nmr spectroscopic studies have revealed that at room temperature ethylamine easily gives a σ-adduct at C-4, yielding a 4-(ethylamino)-3,4-dihydropteridine derivative. t-Butylamine, however, only gives with the pteridines addition at C-4 at low temperature, i.e. at ?40°. This adduct dissociates at room temperature. n-Propylamine and n-butylamine show the same behavior as ethylamine.     

Chlorination of aromatic compounds in micellar media: regioselectivity

Chlorination of phenol and ortho-chlorophenol was studied in micellar media in order to observe the effect on regioselectivity. Hydrogen peroxide/hydrochloric acid-aqueous system, which is environmentally a safer route was employed for chlorination. Selectivity ratio was found to be dependent on the nature and concentration of the surfactant. Ortho/para selectivity ratio up to 12 was realized for the chlorination of phenol. 2,6-/2,4-dichlorophenol ratio up to 1.01 was realized for the chlorination of ortho-chlorophenol.     

The non-equilibrium ortho/para spin state ratio for molecular H2 formed in the hydrolysis of lithium aluminum hydride

The ortho/para ratio for H₂ formed by reaction of LiAlH₄ with H₂O is <- 2.3 at room temperature, indicating that H₂ is formed in non-equilibrium spin ratios. Presumably only a few states of H₂ are initially formed in the reaction.     

Amine-induced lossen rearrangements of 3-hydroxy-5,6-dihydrouracil and N-hydroxysuccinimide benzenesulfontes

The reaction of sodium succinohydroxamate with benzenesulfonyl chloride yielded 3-benzene-sulfonyloxy-5,6-dihydrouracil, 3 . Treatment of 3 with ammonia, aniline, t-butylamine or piperidine yielded a mixture of the requisite 1,2-bis(ureido)ethane and 1-curboxamido-2-imidazolidone. Acylation of N-hydroxysuccinimide with benzenesulfonyl chloride furnished N-benzenesulfonyl-oxysuccinimide, 10. Aniline or t-butylamine were used as representative amines to demonstrate their capability of inducing a Lossen degradation on 10 to afford the corresponding β-ureido -propionamide.     

Active intermediates for the selective chlorination of chlorobenzene in the antimony pentachloride–sulfur-containing compound catalytic system

Ionic complexes of trichlorosulfonium, phenyldichlorosulfonium, and bis(p-chlorophenyl)chlorosulfonium hexachloroantimonates have been synthesized. Chlorination of chlorobenzene with the synthesized complexes and chlorine in the presence of the catalytic systems SbCl₅-sulfur-containing compounds (SCl₂, Ph₂S, Ph₂S₂) has been carried out. The close values of the para/ortho ratio of the dichlorobenzenes in these pairs of reactions provides a basis for considering that chlorosulfonium hexachloroantimonates are the para-selective intermediates in the chlorination of chlorobenzene.     

Rhodium‐Catalyzed meta‐C−H Functionalization of Arenes

Rhodium‐catalyzed ortho ‐C−H functionalization is well known in the literature. Described herein is the Xphos‐supported rhodium catalysis of meta ‐C−H olefination of benzylsulfonic acid and phenyl acetic acid frameworks with the assistance of a para ‐methoxy‐substituted cyano phenol as the directing group. Complete mono‐selectivity is observed for both scaffolds. A wide range of olefins and functional groups attached to arene are tolerated in this protocol.     

“Meta Elimination,” a Diagnostic Fragmentation in Mass Spectrometry

The diagnostic value of the “ortho effect” for unknown identification by mass spectrometry is well known. Here, we report the existence of a novel “meta effect,” which adds to the repertoire of useful mass spectrometric fragmentation mechanisms. For example, the meta-specific elimination pathway described in this report enables unequivocal identification of meta isomers from ortho and para isomers of carboxyanilides. The reaction follows a specific path to eliminate a molecule of meta-benzyne, from the anion produced after the initial decarboxylation of the precursor. Consequently, in the CID spectra of carboxyanilides, a peak for the (R-CO-NH)^– anion is observed only for the meta isomers. For example, the peaks observed at m/z 58, 86, 120, 128, and 170 from acetamido-, butamido-, benzamido, heptamido-, and decanamido-benzoates, respectively, were specific only to the spectra of meta isomers.     

高邻位高分子量热塑性酚醛树脂研制

改变传统合成工艺,在高温高压无催化剂条件下,合成了无金属杂质的高邻位高分子量热塑性酚醛树脂。考察了苯酚与甲醛加成缩合反应过程中原料种类、原料配比、反应温度及反应压力等因素对酚醛树脂结构性能的影响。通过软化点测试仪、核磁共振谱仪等研究了酚醛树脂合成过程中各个参数对酚醛树脂结构性能的影响。在酚／醛比为1：0．7,210℃、...     

Amine exchange reactions of 3-<Emphasis Type="Italic">tert</Emphasis>-butyl-6-(methylsulfanyl)-1,2,3,4-tetrahydro-1,3,5-triazine hydroiodide with amino acids

3-tert-Butyl-6-(methylsulfanyl)-1,2,3,4-tetrahydro-1,3,5-triazine hydroiodide enters into the amine exchange reaction with glycine and β-alanine in aqueous solution. The final exchange products are [4-(methylsulfanyl)-5,6-dihydro-1,3,5-triazin-3-ium-1(2H)-yl] acetate and 3-[4-(methylsulfanyl)-5, 6-dihydro-1,3,5-triazin-3-ium-1(2H)-yl] propanoate, respectively, crystallizing together with t-butylamine hydroiodide from aqueous or aqueous alcoholic solutions as ion associates, which also can be detected in solution in DMSO-d ₆. [4-(Methylsulfanyl)-5,6-dihydro-1,3,5-triazin-3-ium-1(2H)-yl] acetate can be extracted directly from the reaction mixture after carrying out the amine exchange in aqueous isopropanol or 95% ethanol, as well as by “recrystallization“ of its associate with tert-butylamine hydroiodide from aqueous isopropanol.     

Kinetics of oxidation of some ortho,meta, and para substituted S-phenylmercaptoacetic Acids by N-Chloro-3-Methyl-2,6-Diphenyl piperidin-4-one in buffered ethanol-water

The kinetics of oxidation of a number of ortho, meta, and para substituted S-phenylmercaptoacetic acids by N-Chloro-3-Metyl-2,6-Diphenylpiperidin-4-one (NCP) has been studied in buffered ethanol-water (75:25 v/v) of pH 5.46. The reaction is of first order each in [oxidant] and [substrate]. The rate constant decreases with increase in pH from 5.22 to 5.70. The reaction is accelerated by electron releasing and retarded by electron withdrawing substitutents. The ρ value obtained for this reaction is ?1.88 at 10°C with a good correlation coefficient of 0.99 showing an electron deficient transition state. The effect of ortho substitutents also is discussed in detail.     

Gold‐Catalyzed Suzuki Coupling of ortho‐Substituted Hindered Aryl Substrates

A method that allows hindered ortho ‐substituted aryl iodides to be efficiently coupled to phenylboronic acid using a gold‐catalyzed C−C bond formation is presented. The use of a molecularly‐defined dinuclear gold chloride catalytic precursor that is stabilized by a new tetradentate (N ,N′ )‐diamino‐(P,P′ )‐diphosphino ferrocene hybrid ligand in a Suzuki‐type reaction is described for the first time. Electron‐rich isopropyl groups on phosphorus were found essential for a superior activity, while the performances of a set of analogous gold dinuclear complexes that were fully characterized by multinuclear NMR spectroscopy and XRD analysis, were investigated. Therefore, arylation of para and ortho ‐substituted iodoarenes bearing electron‐rich, electron‐poor functional groups, and even hindered polycyclic aromatic compounds is described.     

Noncatalytic kinetic study on site-selective H/D exchange reaction of phenol in sub- and supercritical water

The site-selective H/D exchange reaction of phenol in sub- and supercritical water is studied without added catalysts. In subcritical water in equilibrium with steam at 210-240 degrees C, the H/D exchange proceeds both at the ortho and para sites in the phenyl ring, with no exchange observed at the meta site. The pseudo-first-order rate constants are of the order of 10(-4) s(-1); 50% larger for the ortho than for the para site. In supercritical water, the exchange is observed also at the meta site with the rate constant in the range of 10(-6)-10(-4) s(-1). As the bulk density decreases, the exchange slows down and the site selectivity toward the ortho is enhanced. The enhancement is due to the phenol-water interaction preference at the atomic resolution. The site selectivity toward the ortho is further enhanced when the reaction is carried out in benzene/water solution. Using such selectivity control and the reversible nature of the hydrothermal deuteration/protonation process, it is feasible to synthesize phenyl compounds that are deuterated at any topological combination of ortho, meta, and para sites.     

Conformational isomerism of 2-carboazetidines

A number of 1-alkyl-2-carboazetidines have been prepared from the reaction of primary amines with α,γ-dibromocarbonyl compounds. Several of these new azetidines exhibit doublet carbonyl stretching absorptions in their infrared spectra. A possible explanation of this phenomenon is offered in terms of three rotational conformers which represent various degrees of dipole-dipole and steric interactions. The cis and trans forms of 1-t-butyl-2-carbomethoxy-4-methylazetidine have been obtained from the reaction of t-butylamine with methyl α,γ-dibromovalerate. A detailed examination indicates that the ir and nmr spectra of these epimers are in agreement with the foregoing conformational postulates.     

Stereoselective and regioselective reaction of cyclic ortho esters with phenols

Cyclic ortho esters undergo stereoselective and regioselective reaction with phenols when treated with BF(3) x OEt(2) at low temperatures. Attack of the phenol on the ortho ester occurs at an open carbon para to electron-donating groups on the phenol ("C-addition") or at the phenolic hydroxyl group ("O-addition") depending on the nature of the cation formed from reaction of the ortho ester and BF(3) x OEt(2). Products resulting from O-addition undergo reversion to a mixture of starting phenol, C-addition product, and O-addition product if treated with BF(3) x OEt(2) at room temperature, but C-addition products are stable under the same conditions. X-ray structural analysis of the C-addition compound indicates that its stereochemistry is opposite to that observed in reaction of similar ortho esters with chloride from TMSCl. However, the stereochemistry of the reaction can be rationalized by the ability of the ortho ester to isomerize via an intermediate benzylic cation and examination of the preferred trajectory of attack of the nucleophile on the intermediate oxonium ion.     

Kinetics and mechanism of oxidation of anisole and substituted anisoles by acid bromate in acetic acid-water mixture

Oxidation of anisoles by acid bromate has been studied in acetic acid-water system in the presence of sulphuric acid. The reaction is first order each in [anisole] and [Br(V)]. The rate of reaction increased with increase in [H⁺] and percentage of acetic acid. The products of oxidation have been identified as ortho and para hydroxyanisoles. From the effect of [H⁺] and [acetic acid] on rate, H ₂ ⁺ BrO₃ has been established as the reactive species. Anisoles having electron-donating substituents in the benzene ring accelerate the rates and vice versa with a Hammett ρ value of −0.6. A mechanism involving the attack of H ₂ ⁺ BrO₃ on ortho/para position of the anisole in the rate-determining step has been proposed.     

Determination of molecular weight distributions of novolac resins by gel permeation chromatography

The number- and weight-average molecular weights of several statistical and high ortho novolac resins were determined using gel permeation chromatography (GPC). The standards used were pure compounds having between 2 and 12 phenol units bridged via methylene linkages. Three series of compounds were studied: (i) those with methylene linkages substituted in only the ortho positions relative to the phenolic hydroxyl group; (ii) those in which all para positions, together with sufficient ortho positions, were used to synthesize the compounds; and (iii) those in which the methylene linkages were substituted at a mixture of ortho and para positions. Such compounds, having known molecular architecture and units similar to the segments of industrial novolac resins, provide for a more exact measurement of the molecular weight than do the commonly used poly(styrene) standards. Using these new standards the number average molecular weights of the resins determined by GPC were in good agreement with the average molecular weight obtained by ¹H-NMR spectra of the resins, particularly for low molecular weight resins. GPC analysis of higher molecular weight resins tends to underestimate the molecular weights because of complications introduced by hydrogen bonding. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1399–1407, 1997     

Adsorption and microcalorimetric investigations ofn-butylamine intercalation in α- and γ-zirconium phosphates

The intercalation process ofn-butylamine was investigated. The adsorption ofn-butylamine in interlamellar space had stepwise character in case of both crystalline forms of zirconium phosphate. The intercalatedn-butylamine existed at low concentration as bilayered complex. The reaction heat was determined by a microcalorimetric method. It was found that about 90% of it refers to the neutralization ofn-butylamine and only about 10% is related with surface adsorption (ion exchange). The steps of adsorption are 6.0 J/g and 1.0 J/g reaction heat values, respectively. The enthalpy balance of total process in dilute solution system (c ₀=3.0 vol%) is 14.67 kJ/mol. The calculated value for ion adsorption (exchange) was 1.37 kJ/mol.     

Gas-phase thermolysis of t-butylsulfenamides: N,N-dimethyl t-butylsulfenamide, 2,6-dimethylpiperidinyl t-butylsulfenamide,and N-t-butyl t-butylsulfenamide

The amide derivatives of t-butylsulfenic acid mentioned in the title have been thermolyzed in a stirred-flow reactor at temperatures of 273–390°C and pressures of 7–15 torr, using toluene as carrier gas, at residence times of 0.4–2 s. Isobutene formed in 95–99% yields, through order one reactions, following the Arrhenius equations: N, N-dimethyl t-butylsulfenamide: These thermolyses are considered to take place through unimolecular, four-center cyclic transition-state reaction mechanisms, giving rise to isobutene plus the corresponding S-unsubstituted thiohydroxylamines. The latter decompose outside the reactor at temperatures above −78°C forming free sulfur and dimethylamine, 2,6-dimethylpiperidine, and t-butylamine, respectively. © 1996 John Wiley & Sons, Inc.     

Synthesis,Characterization and Redox Properties of Three New <Emphasis Type="Italic">vic</Emphasis>-dioximes and their Nickel(II) Metal Complexes

Three novel vic-dioximes: cyclohexylamine-p-tolylglyoxime (L₁H₂), t-butylamine-p-tolylglyoxime (L₂H₂) and sec-butylamine-p-tolylglyoxime (L₃H₂) were prepared by the reaction of anti-p-tolylchloroglyoxime with cyclohexylamine, t-butylamine and sec-butylamine in absolute THF. The detection of H-bonding in all of the Ni(II) complexes by i.r. revealed the square-planar MN₄ coordination of mononuclear complexes. MN₄ coordination of the [(L₁H)₂Ni] complex was also determined by ¹H and ¹³C-n.m.r spectroscopy. Mononuclear complexes with a 1:2 metal-ligand ratio were prepared using Ni(II) salts. All Ni(II) complexes are insoluble in common solvents. The ligands and complexes were characterized by elemental analyses, FT-i.r., u.v.–vis., ¹H and ¹³C-n.m.r. spectra, magnetic susceptibility measurements, thermogravimetric analyses (t.g.a.) and cyclic voltammetry.