Kinetic study of the reactions of Cl atoms with CF3CH2CH2OH, CF3CF2CH2OH, CHF2CF2CH2OH, and CF3CHFCF2CH2OH

The reaction kinetics of chlorine atoms with a series of partially fluorinated straight-chain alcohols, CF(3)CH(2)CH(2)OH (1), CF(3)CF(2)CH(2)OH (2), CHF(2)CF(2)CH(2)OH (3), and CF(3)CHFCF(2)CH(2)OH (4), were studied in the gas phase over the temperature range of 273-363 K by using very low-pressure reactor mass spectrometry. The absolute rate coefficients were given by the expressions (in cm(3) molecule(-1) s(-1)): k(1) = (4.42 +/- 0.48) x 10(-11) exp(-255 +/- 20/T); k(1)(303) = (1.90 +/- 0.17) x 10(-11), k(2) = (2.23 +/- 0.31) x 10(-11) exp(-1065 +/- 106/ T); k(2)(303) = (6.78 +/- 0.63) x 10(-13), k(3) = (8.51 +/- 0.62) x 10(-12) exp(-681 +/- 72/T); k(3)(303) = (9.00 +/- 0.82) x 10(-13) and k(4) = (6.18 +/- 0.84) x 10(-12) exp(-736 +/- 42/T); k(4)(303) = (5.36 +/- 0.51) x 10(-13). The quoted 2sigma uncertainties include the systematic errors. All title reactions proceed via a hydrogen atom metathesis mechanism leading to HCl. Moreover, the oxidation of the primarily produced radicals was investigated, and the end products were the corresponding aldehydes (R(F)-CHO; R(F) = -CH(2)CF(3), -CF(2)CF(3), -CF(2)CHF(2), and -CF(2)CHFCF(3)), providing a strong experimental indication that the primary reactions proceed mainly via the abstraction of a methylenic hydrogen adjacent to a hydroxyl group. Finally, the bond strengths and ionization potentials for the title compounds were determined by density functional theory calculations, which also suggest that the alpha-methylenic hydrogen is mainly under abstraction by Cl atoms. The correlation of room-temperature rate coefficients with ionization potentials for a set of 27 molecules, comprising fluorinated C2-C5 ethers and C2-C4 alcohols, is good with an average deviation of a factor of 2, and is given by the expression log(k) (in cm(3) molecule(-1) s(-1)) = (5.8 +/- 1.4) - (1.56 +/- 0.13) x (ionization potential (in eV)).     

Synthesis of 2-hetaryl-2-(tetrahydrofuran-2-ylidene)acetonitriles

The reaction of azolylacetonitriles with γ-chlorobutyryl chlorides gave the corresponding 2-(1-R-1,3-di- hydro-2H-benzimidazol-2-ylidene)-, 2-(1,3-benzothiazol-2-ylidene)-, and 6-chloro-2-(4-methylthiazol-2-ylidene)-3-oxohexanenitriles. A study of the intramolecular cyclization of 2-(quinazolin-2-ylidene)-3-oxo-6-hexanenitriles and -heptanenitriles has led to the development of an efficient method for the preparation of 2-(quinazolin-2-yl)-2-(tetrahydrofuran-2-ylidene)acetonitriles. The (Z,E)-isomerism of the synthesized 2-hetaryl-2-(tetrahydrofuran-2-ylidene)acetonitriles was studied.     

Reactions of 2-amino- and 2-hydrazinobenzimidazoles with 2-acyldimedones

The reaction of 2 formyldimedone with 2-amino- and 2-hydrazinobenzimidazoles at 20°C in ethanol gave 2-(2-benzimidazolyl)aminomethylene- and 2-[2-(2-benzimidazolyl)hydrazinomethylene]-5,5-dimethylcylohex-anediones, while this reaction carried out in ethanol at reflux in the presence of acid gave 2,2-dimethyl-4-oxo 1, 2, 3, 4-tetrahydroquinazolino(1, 2-a]benzimidazole and 1-(2-benzimidazolyl)-6, 6-dimethyl-4-oxo-4, S, 6, 7-tetrahydroindazole, respectively.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 247–252, February, 1996.     

Synthesis of 3-substituted-2-benzothiazolinone, 2-benzoxazolinone and benzothiazoline-2-thione

The reaction of 2-benzothiazolinone, 2-benzoxazolinone or benzothiazoline-2-thione under basic conditions with various electrophiles afforded the titled compounds 1-13, 29-31 and 40-48. The 3-(substituted-aminomethyl)-2-benzothiazolinone and related compounds 14-25 were prepared by the reaction of 3-(hydroxymethyl)-2-benzothiazolinone or the appropriate 2-benzothiazolinone and formaldehyde with the appropriate amine or substituted aniline. The reaction of 9, 13 or 25 with methyl iodide afforded the quaternary ammonium iodides 26-28. The reaction of the appropriate potassium salts of various phenol with 3-(chloromethyl)-2-benzothiazolinone afforded the 3-(substituted-phenoxymethyl)-2-benzothiazolinone and related compounds 32-39. The ethyl or isopropylxanthates 49-54 were synthesized by the reaction of 3-(chloromethyl)-2-benzo-thiazolinone and appropriate compounds with potassium ethyl or isopropyl xanthate. The reaction of 3-(chloromethyl)-2-benzothiazolinone with sodium sulfide afforded the sulfide 55.     

Disproportionation pathways of aqueous hyponitrite radicals (HN2O2(*)/N2O2(*-))

Pulse radiolysis and flash photolysis are used to generate the hyponitrite radicals (HN2O2(*)/N2O2(*-)) by one-electron oxidation of the hyponitrite in aqueous solution. Although the radical decay conforms to simple second-order kinetics, its mechanism is complex, comprising a short chain of NO release-consumption steps. In the first, rate-determining step, two N2O2(*-) radicals disproportionate with the rate constant 2k = (8.2 +/- 0.5) x 10(7) M(-1) s(-1) (at zero ionic strength) effectively in a redox reaction regenerating N2O2(2-) and releasing two NO. This occurs either by electron transfer or, more likely, through radical recombination-dissociation. Each NO so-produced rapidly adds to another N2O2(*-), yielding the N3O3(-) ion, which slowly decomposes at 300 s(-1) to the final N2O + NO2(-) products. The N2O2(*-) radical protonates with pKa = 5.6 +/- 0.3. The neutral HN2O2(*) radical decays by an analogous mechanism but much more rapidly with the apparent second-order rate constant 2k = (1.1 +/- 0.1) x 10(9) M(-1) s(-1). The N2O2(*-) radical shows surprisingly low reactivity toward O2 and O2(*-), with the corresponding rate constants below 1 x 10(6) and 5 x 10(7) M(-1) s(-1). The previously reported rapid dissociation of N2O2(*-) into N2O and O(*-) does not occur. The thermochemistry of HN2O2(*)/N2O2(*-) is discussed in the context of these new kinetic and mechanistic results.     

2'-O-[2-(amino)-2-oxoethyl] oligonucleotides

[structure: see text] Oligonucleotides with novel modifications, 2'-O-[2-(amino)-2-oxoethyl] (2'-O-NAc), 2'-O-[2-(methylamino)-2-oxoethyl] (2'-O-NMAc), 2'-O-[2-(dimethylamino)-2-oxoethyl] (2'-O-DMAc), and 2'-O-[2-[[2-(dimethylamino)ethyl]amino]-2-oxoethyl] (2'-O-DMAEAc), have been synthesized. These modified oligonucleotides exhibit high binding affinity to complementary RNA (and not to DNA) and considerably enhance the nuclease stability of oligonucleotides with t(1/2) > 24 h.     

5-(Trimethylstannyl)-2H-pyran-2-one and 3-(Trimethylstannyl)-2H-pyran-2-one: New 2H-Pyran-2-one Synthons

5-(Trimethylstannyl)-2H-pyran-2-one (11) and 3-(trimethylstannyl)-2H-pyran-2-one (30), readily prepared from the corresponding bromo-2H-pyran-2-ones, undergo Pd(0)-catalyzed coupling reactions with a variety of enol triflates to give 5- and 3- substituted 2H-pyran-2-ones, respectively. This reaction is applicable to the enol triflates of 14beta-hydroxy-17-ketosteroids, and therefore may prove useful in convergent syntheses of lucibufagins and bufadienolides.     

Synthesis and properties of 2-(2-furyl)-and 2-(2-Thienyl)-1,3-benzoxazoles

Condensation of o-aminophenol with furoyl and thenoyl chlorides in 1-methylpyrrolidin-2-one gave, respectively, 2-(2-furyl)- and 2-(2-thienyl)-1,3-benzoxazoles in which the furan and thiophene rings showed no acidophobic properties. Reactions of 2-(2-furyl)- and 2-(2-thienyl)-1,3-benzoxazoles with electrophilic reagents (acylation, bromination, nitration, and sulfonation) afforded products of hydrogen replacement in both hetaryl and benzene rings, depending on the conditions.     

Reaction of 2-hetaryl-2-(tetrahydro-2-furanylidene)acetonitriles with aldehydes

The reaction of 2-hetaryl-2-(tetrahydro-2-furanylidene)acetonitriles with a electrophilic reagent (anisaldehyde) was studied. It was shown that condensation of the latter with 2-(4-oxo-3,4-dihydro-2-quinazolyl)- and 2-(1H-benzo[d]imidazol-2-yl)-2-(tetrahydro-2-furanylidene)acetonitriles in the presence of secondary amines or acids takes place with elimination of the furan fragment and the formation of 3-aryl-2-(4-oxo-3,4-dihydro-2-quinazolinyl)- and 2-(1H-benzo[d]imidazol-2-yl)acrylo-nitriles.     

2-[2-(1,4-benzodioxanyl) ]-2-imidazoline hydrochloride

A new synthesis of 2-[2-(1,4-benzodioxanyl)]-2-imidazoline hydrochloride from 2-cyano-benzodioxan is described and the previously claimed route to this compound is shown to give a formula isomer, ie. 2-methyl-2-[2-(1,3-benzodioxolyl)]-2-imidazoline hydrochloride.     

Syntheses on the basis of 2H-chromen-2-one and 2H-chromene-2-thione

4-Hydroxy-2H-chromen-2-one and 4-hydroxy-2H-chromene-2-thione reacted with allyl bromide, 1,1,3-trichloroprop-1-ene, and 1,3-dichlorobut-2-ene to give the corresponding ethers, which were oxidized to (2-oxo-2H-chromen-4-yloxy)acetic acid with potassium permanganate, and various derivatives of that acid were obtained. 3-(3,3-Dichloroprop-2-enyl)-7-hydroxy-4-methyl-2H-chromen-2-one and 3-(3,3-dichloroprop-2-enyl)-7-hydroxy-4-methyl-2H-chromene-2-thione were synthesized, and some their transformations were studied.     

Quenching of I(2P1/2) by NO2, N2O4, and N2O

Quenching of excited iodine atoms (I(5p5, 2P1/2)) by nitrogen oxides are processes of relevance to discharge-driven oxygen iodine lasers. Rate constants at ambient and elevated temperatures (293-380 K) for quenching of I(2P1/2) atoms by NO2, N2O4, and N2O have been measured using time-resolved I(2P1/2) --> I(2P3/2) 1315 nm emission. The excited atoms were generated by pulsed laser photodissociation of CF3I at 248 nm. The rate constants for I(2P1/2) quenching by NO2 and N2O were found to be independent of temperature over the range examined with average values of (2.9 +/- 0.3) x 10(-15) and (1.4 +/- 0.1) x 10(-15) cm3 s(-1), respectively. The rate constant for quenching of I(2P1/2) by N2O4 was found to be (3.5 +/- 0.5) x 10(-13) cm3 s(-1) at ambient temperature.     

Cl_2 2HI=2HCl I_2反应机理的理论研究

分别在MP2/3-21G!!、CCSD(T)/3-21G!!//MP2/3-21G!!和B3LYP/3-21G!!3种水平上,计算研究了气相反应Cl2 2HI=2HCl I2的机理,求得一系列四中心和三中心的过渡态.通过比较六种反应通道的活化能大小,得到了相同的结论:双分子基元反应Cl2 HI"HCl ICl和ICl HI"I2 HCl的最小活化能小于Cl2、HI和ICl的解离能,从理论上证明了反应Cl2 2HI=2HCl I2将优先以分子与分子作用形式分两步完成.用内禀反应坐标(IRC)验证了MP2/3-21G!!方法计算得到的过渡态.     

Crystal Structures of [Bu2Sn(O2PPh2)2], [Ph2Sn(O2PPh2)2], and [PhClSn(O2PPh2)OMe]2. Raman Spectra of [Ph2Sn(O2PPh2)2] and [PhClSn(O2PPh2)OMe]2

[(n‐Bu)₂Sn(O₂PPh₂)₂] ( 1 ), and [Ph₂Sn(O₂PPh₂)₂] ( 2 ) have been synthesized by the reactions of R₂SnCl₂ (R=n‐Bu, Ph) with HO₂PPh₂ in Methanol. From the reaction of Ph₂SnCl₂ with diphenylphosphinic acid a third product [PhClSn(O₂PPh₂)OMe]₂ ( 3 ) could be isolated. X‐ray diffraction studies show 1 to crystallize in the monoclinic space group P2₁/c with a = 1303.7(1) pm, b = 2286.9(2) pm, c = 1063.1(1) pm, β = 94.383(6)°, and Z = 4. 2 crystallizes triclinic in the space group , the cell parameters being a = 1293.2(2) pm, b = 1478.5(4) pm, c = 1507.2(3) pm, α = 98.86(3)°, β = 109.63(2)°, γ = 114.88(2)°, and Z = 2. Both compounds form arrays of eight‐membered rings (SnOPO)₂ linked at the tin atoms to form chains of infinite length. The dimer 3 consists of a like ring, in which the tin atoms are bridged by methoxo groups. It crystallizes triclinic in space group with a = 946.4(1) pm, b = 963.7(1) pm, c = 1174.2(1) pm, α = 82.495(6)°, β = 66.451(6)°, γ = 74.922(6)°, and Z = 1 for the dimer. The Raman spectra of 2 and 3 are given and discussed.     

Photocycloaddition of 2-Cyanocycloalk-2-Enones to 2, 3-Dimethylbut-2-Ene

Irradiation of 5,5-dimethyl-6-oxocyclohex- l-ene- l-carbonitrile ( 1 ) in the presence of 2,3-dimethylbut-2-ene afforded 3,3,4,4,7,7-hexamethyl-3,4,4a,5,6,7-hexahydroindeno[1,7-c,d]-],2-oxazole (3) in nearly quantitative yield. In contrast, 4,4-dimethyl-5-oxo-cyclopent-l-ene-l-carbonitrile ( 2 ) under the same conditions reacted not to a tricyclic isoxazole but to a 2:1 mixture of 3,3,6,6,7,7-hexamethyl-2-oxo-bicyclo[3.2.0]heptane-l-carbonitrile ( 4 ) and trans-3,3-dimethyl-2-oxo-5-(2,3-dimethylbut-3-en-2-yl)cyclopentane-l-carbonitrile ( 5 ), respectively.     

2MgO·2B2O3·MgCl2·14H2O-7.8%H3BO3-H2O体系多温相关系研究

研究了2MgO·2B2O3·MgCl2·14H20在不同温度下的7.8%H3BO3水溶液中的相转化产物及其溶解度.IR,XRD,TG及化学分析表明,相转化产物在0～22℃范围内为MgO·2B2O3·9H20;22～68℃为MgO·2B2O3·7.5H20;68～95℃为MgO·2B2O3·7H20;95～98.8℃为MgO·2B2O3·5H20;100～110℃为MgO·B2O3·3H20;110～120℃为2MgO·B2O3·2H20;120～170℃为2MgO·B2O3·1.5H20;170～200℃为2MgO·B2O3·H20.提出了相转化反应原理.     

Synthesis and structures of complexes ofN-2-nitroxyethylpicolinamide and 2-(2-pyridyl)-2-oxazoline with PdCl2

The reaction ofN,N′-bis(2-nitroxyethyl)pyridine-2,6-dicarboxamide with PdCl₂ afforded previously unknowncis-(N-2-nitroxyethylpicolinamide-N,N′)dichloropalladium(II) andcis-[2-(2-pyridyl)-2-oxazoline-N,N′]dichloropalladium(II), which were isolated as a cocrystallizate of the molecular compounds. Its structure was established by X-ray diffraction analysis. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1604–1606, August, 1999.     

2-(2-hydroxyphenyl)-2-adamantanol in Ritter reaction

2-Substituted 4H-1,3-benzoxazines were obtained by the condensation of 2-(2-hydroxyphenyl)-2-adamantanol with aromatic and aliphatic nitriles in trifluoroacetic acid. With acetonitrile the classic product of Ritter reaction, a secondary amide, was isolated.     

二氯菊酸2－甲基－3－（2－呋喃基）－2－丙烯酯的合成

报导了一种新拟除虫菊酯的设计和合成。标题化合物是由二氯菊酰氯与新自制的２－甲基－３－（２－呋喃基）－２－丙烯－１－醇酯化合成。     

The hydroxyacetylpiperidines and their N-benzyl derivatives. The 2-hydroxymethyl-2-piperidyl- and 2-hydroxymethyl-2-pyridyl-1,3-dioxolanes

The hydroxyacetylpiperidines, their ethylene ketals, and the N-benzyl derivatives of these new piperidines have been synthesized. Methylolation of 2-(2- and 4-pyridyl)-1,3-dioxolanes by heating with paraformaldehyde at 185° led to 2-hydroxymethyl-2-(2- and 4-pyridyl)-i,3-dioxolanes ( 7,8 , respectively). 2-Hydroxymethyl-2-(3-pyridyl)-1,3-dioxolane ( 13 ) was obtained by reaction of 2-bromomethyl-2-(3-pyridyl)-1,3-dioxolane with aqueous sodium hydroxide at 190°. Hydrogenation of these pyridine ketals with rhodium-charcoal catalyst produced the corresponding piperidine ketals (16,17,18). Acid hydrolysis of the piperidine ketals and their N-benzyl derivatives led to the hydroxyacetylpiperidines (1,2,3) and their N-benzyl derivatives (25,26,27). The N-benzylhydroxyacetylpiperidines undergo rapid hydrogenolysis with palladium-charcoal catalyst to produce the hydroxyacetylpiperidines. Further hydrogenation produces the piperidyl-1,2-ethanediols. The hydroxyacetylpiperidines are somewhat unstable, hygroscopic substances which polymerize with dehydration on standing; in solution they are relatively stable. Their N-benzyl, ketal, and hydrochloride salt derivatives, on the other hand, represent stable, synthetically useful intermediates from which the reactive trifunctional hydroxyacetylpiperidines may readily be prepared.