- Radical Carbonyl Propargylation by Dual Catalysis
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Carbonyl propargylation has been established as a valuable tool in the realm of carbon–carbon bond forming reactions. The 1,3-enyne moiety has been recognized as an alternative pronucleophile in the above transformation through an ionic mechanism. Herein, we report for the first time, the radical carbonyl propargylation through dual chromium/photoredox catalysis. A library of valuable homopropargylic alcohols bearing all-carbon quaternary centers could be obtained by a catalytic radical three-component coupling of 1,3-enynes, aldehydes and suitable radical precursors (41 examples). This redox-neutral multi-component reaction occurs under very mild conditions and shows high functional group tolerance. Remarkably, bench-stable, non-toxic, and inexpensive CrCl3 could be employed as a chromium source. Preliminary mechanistic investigations suggest a radical-polar crossover mechanism, which offers a complementary and novel approach towards the preparation of valuable synthetic architectures from simple chemicals.
- Huang, Huan-Ming,Bellotti, Peter,Daniliuc, Constantin G.,Glorius, Frank
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supporting information
p. 2464 - 2471
(2020/12/07)
-
- PROCESS FOR THE PRODUCTION OF FERROPORTIN INHIBITORS
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The invention relates to a new process for preparing compounds of the formula (I) and pharmaceutically acceptable salts thereof, which act as ferroportin inhibitors being suitable for the use as medicaments in the prophylaxis and/or treatment of diseases caused by a lack of hepcidin or of iron metabolism disorders leading to increased iron levels or increased iron absorption, including iron overload, thalassemia, sickle cell disease and hemochromatosis.
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Page/Page column 33-34; 43-46
(2021/10/02)
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- Compounds and methods for the reduction of halogenated hydrocarbons
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The present application relates to methods for the reduction of halogenated hydrocarbons using compounds of Formula (I): wherein the reduction of the halogenated compounds is carried out, for example, under ambient conditions without the need for a transition metal containing co-factor. The present application also relates to methods of recovering precious metals using compounds of Formula (I) that are absorbed onto a support material.
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Page/Page column 19
(2017/12/27)
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- Ultrasonically Assisted Decarboxylative Bromination of α,β-Unsaturated Carboxylic Acids under Vilsmeier-Haack Conditions
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An efficient method for decarboxylative bromination of cinnamic acids (α,β-unsaturated carboxylic acids or 3-arylpropenoic acids) was achieved under relatively mild conditions using Vilsmeier-Haack reagent and KBr in acetonitrile media. Vilsmeier-Haack reagent is prepared by using 1:1 ratio of oxychloride (SOCl2 or POCl3) and DMF under chilled condition. Ultrasonically assisted reactions underwent smoothly with highly significant rate enhancements and afforded bromostyrenes as products in very good yields even though the reactions were too sluggish.
- Kumar, M. Satish,Rajanna,Venkanna,Venkateswarlu,Sudhakar Chary
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p. 642 - 646
(2015/12/26)
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- Synthetic methods and intermediates for the preparation of xenicanes
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The invention provides novel synthetic intermediates and synthetic methods that are useful for preparing compounds of the xenicane family. Certain compounds of the invention may also possess anti-cancer properties.
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Page/Page column
(2014/09/03)
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- Total synthesis and biological evaluation of (-)-9-deoxy-englerin a
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An effective total synthesis of (-)-9-deoxy-englerin (4), an analogue of the natural guaiane sesquiterpene englerin A (1), has been achieved. The synthesis features a transannular epoxide opening to construct the 5,7-fused ring system followed by transannular ether formation with mercury(II) trifluoroacetate.
- Ushakov, Dmitry B.,Navickas, Vaidotas,Strobele, Markus,Maichle-Moessmer, Caecilia,Sasse, Florenz,Maier, Martin E.
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supporting information; experimental part
p. 2090 - 2093
(2011/06/22)
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- Unimolecular reactions of CH2BrCH2Br, CH 2BrCH2Cl, and CH2BrCD2Cl: Identification of the Cl-Br interchange reaction
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The recombination reactions of CH2Br and CH2Cl radicals have been used to generate vibrationally excited CH 2BrCH2Br and CH2BrCH2Cl molecules with 91 kcal mol-1 of energy in a room-temperature bath gas. The experimental unimolecular rate constants for elimination of HBr and HCl were compared to calculated statistical rate constants to assign threshold energies of 58 kcal mol-1 for HBr elimination from C2H 4Br2 and 58 and 60 kcal mol-1, respectively, for HBr and HCl elimination from C2H4BrCl. The Br-Cl interchange reaction was demonstrated and characterized by studying the CH 2BrCD2Cl system generated by the recombination of CH 2Br and CD2Cl radicals. The interchange reaction was identified from the elimination of HBr and DCl from CH2ClCD 2Br. The interchange reaction rate is much faster than the rates of either DBr or HCl elimination from CH2BrCD2Cl, and a threshold energy of ?43 kcal mol-1 was assigned to the interchange reaction. The statistical rate constants were calculated from models of the transition states that were obtained from density functional theory using the B3PW91 method with the 6-31G(d′,p′) basis set. The model for HBr elimination was tested versus published thermal and chemical activation data for C2H5Br. A comparison of Br-Cl interchange with the Cl-F and Br-F interchange reactions in 1,2-haloalkanes is presented.
- Friederich, Laura,Duncan, Juliana R.,Heard, George L.,Setser,Holmes, Bert E.
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experimental part
p. 4138 - 4147
(2010/09/04)
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- Pyrolysis of α- and β-heteroatoms substituted ethyl phenyl sulfoxides
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A study on the mechanism of the thermal decomposition of α- and β-heteroatoms substituted ethyl phenyl sulfoxides was carried out using 1-chloroethyl phenyl sulfoxide (1); two diastereomeric 1-acetoxyethyl (substituted phenyl) sulfoxides (2a) and (2b); and 2-chloroethyl phenyl, 2-bromoethyl phenyl, and 2-methoxyethyl phenyl sulfoxides (3, 4, 5). The rate of pyrolysis of 1 was 4.8 times faster at 160°C than that of ethyl phenyl sulfoxide used as a reference, while those of 2a and 2b were 107 and 155 times faster, respectively. The results indicate that the lone pair of electrons on the α-heteroatoms has a larger rate acceleration effect than the electronegativity of them. The substituent effects of the phenyl group of 2a and 2b gave positive Hammett ρ-values (ρa= 0.76 and ρb= 0.80 vs. σ). Activation parameters for 2a and 2b are as follows: 2a, ΔH?= 112 kJmol-1, ΔS?= -20 JK-1mol-1; 2b, ΔH?= 107 kJmol-1, ΔS?= -29 JK-1mol-1. Large deuterium kinetic isotope effects for 1-acetoxyethyl-2,2,2-d3 phenyl sulfoxides (2ad and 2bd) were observed (kH/kD= 3.5 ～ 4.1). These results suggest that the pyrolysis of -heteroatom substituted ethyl phenyl sulfoxides proceeds via a five-membered transition state deviated to E1-like in character. On the other hand, from the results of kinetics for the pyrolysis of 3, 4, and 5, no effect by the β-halogen atoms or some deceleration effect by the β-methoxy group was observed. Thus the reaction seems to proceed via an E1-like mechanism. Copyright Taylor & Francis Group.
- Yoshimura, Toshiaki,Sakae, Hironori,Yoshizawa, Masaki,Hasegawa, Kiyoshi,Tsukurimichi, Eiichi
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experimental part
p. 1162 - 1173
(2010/08/06)
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- Synthesis of sulfur-containing aryl and heteroaryl vinyls via Suzuki-Miyaura cross-coupling for the preparation of SERS-active polymers
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The preparation of sulfur-containing aryl and heteroaryl vinyl co-monomers via Suzuki-Miyaura cross-coupling between the corresponding mercaptomethyl arylboronates and in situ-generated vinyl bromides is described. Surface-enhanced Raman scattering (SERS) studies of the target compounds on gold nanoparticles confirmed their potential as spectroscopic tags in the fabrication of SERS-encoded polymers for combinatorial screening and biomedical diagnostics.
- Perez-Pineiro, Rolando,Dai, Sheng,Alvarez-Puebla, Ramon,Wigginton, James,Al-Hourani, Baker Jawabrah,Fenniri, Hicham
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supporting information; experimental part
p. 5467 - 5469
(2010/01/11)
-
- Synthesis of hydroxylated hydrocarbons
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Ethylene glycol, other diols, triols, and polyols are made in an efficient manner by reacting dibromides with water in the presence of a metal oxide. An integrated process of dibromide formation, alcohol synthesis, metal oxide regeneration, and bromine recycling is also provided.
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Page/Page column 5
(2008/06/13)
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- Compounds which mimic the chemical and biological properties of discodermolide
-
Compounds which mimic the chemical and/or biological activity of discodermolide are provided and intermediates useful in their preparation.
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- Mechanism and structure-reactivity correlation in the homogeneous, unimolecular elimination kinetics of 2-substituted ethyl methylcarbonates in the gas phase
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The gas-phase elimination kinetics of 2-substituted ethyl methylcarbonates were determined in a static reaction system over the temperature range of 323-435 °C and pressure range 28.5-242 Torr. The reactions are homogeneous, unimolecular and follow a first-order rate law. The kinetic and thermodynamic parameters are reported. The 2-substituents of the ethyl methylcarbonate (CH3OCOOCH2CH2Z, Z = substituent) give an approximate linear correlation when using the Taft-Topsom method, log(k z/kH)= -(0.57 ± 0.19)σα + (1.34 ± 0.49)σR (r = 0.9256; SD = 0.16) at 400 °C. This result implies the elimination process to be sensitive to steric factors, while the electronic effect is unimportant. However, the resonance factor has the greatest influence for a favorable abstraction of the β-hydrogen of the C3- H bond by the oxygen carbonyl. Because ρα is significant, a good correlation of the alkyl substituents of carbonates with Hancock's steric parameters was obtained: log(kR/kH versus Esc for CH 3OCOOCH2CH2R at 400°C, R = alkyl, δ= -0.17 (r=0.9993, SD = 0.01). An approximate straight line was obtained on plotting these data with the reported Hancock's correlation of 2-alkyl ethylacetates. This result leads to evidence for the β-hydrogen abstraction by the oxygen carbonyl and not by the alkoxy oxygen at the opposite side of the carbonate. The carbonate decompostion is best described in terms of a concerted six-membered cyclic transition state type of mechanism. Copyright
- Chuchani, Gabriel,Marquez, Edgar,Herize, Armando,Dominguez, Rosa Maria,Tosta, Maria,Brusco, Doris
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p. 839 - 848
(2007/10/03)
-
- An integrated process for partial oxidation of alkanes
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The partial oxidation of alkanes via bromination followed by the reaction with solid metal oxide mixtures (MO) is shown to give an array of products that can be tuned by varying the MO and the reaction conditions.
- Zhou, Xiao-Ping,Yilmaz, Aysen,Yilmaz, Gurkan A.,Lorkovic, Ivan M.,Laverman, Leroy E.,Weiss, Michael,Sherman, Jeffrey H.,McFarland, Eric W.,Stucky, Galen D.,Ford, Peter C.
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p. 2294 - 2295
(2007/10/03)
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- Enzyme inhibition immunoassay
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The present invention provides a method for the measurement of an analyte in biological samples whereby an uncompetitive inhibitor is coupled to a ligand and utilized in a homogeneous assay. The analyte can be a drug or drug derivative, hormone, polypeptide, or oligonucleotide. The present invention also provides novel compounds, assay reagents and packaged kits useful for performing such measurements.
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- Simple and efficient protocol for the synthesis of functionalized styrenes from 1,2-dibromoethane and arylboronic acids
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(Matrix presented) A simple and efficient protocol for the preparation of functionalized styrenes is disclosed that employs the palladium-catalyzed cross-coupling reaction of arylboronic acids with vinyl bromide, generated in situ from 1,2-dibromoethane. The reaction is carried out under mild reaction conditions. Compared with the cross-coupling reactions usually employed to obtain vinylarenes, this protocol is very simple, overcomes the inconvenience of using of ethylene under pressure, and uses air-stable and widely available arylboronic acids instead of vinyl organometallic reagents.
- Lando, Vanusa R.,Monteiro, Adriano L.
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p. 2891 - 2894
(2007/10/03)
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- Compounds which mimic the chemical and biological properties of discodermolide
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Compounds which mimic the chemical and/or biological activity of discodermolide are provided and intermediates useful in their preparation.
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- Piperidine derivatives useful as CCR5 antagonists
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The use of CCR5 antagonists of the formula or a pharmaceutically acceptable salt thereof, wherein X is —C(R13)2—, —C(R13)(R19)—, —C(O)—, —O—, —NH—, —N(alkyl)—, R is optionally substituted phenyl, pyridyl, thiophenyl or naphthyl; R1is H, alkyl or alkenyl; R2is optionally substituted phenyl, phenylalkyl, heteroaryl or heteroarylalkyl, naphthyl, fluorenyl or diphenylmethyl; R3is optionally substituted phenyl, heteroaryl or naphthyl; R4is H, alkyl, fluoro-alkyl, cyclopropylmethyl, —CH2CH2OH, —CH2CH2—O-alkyl, —CH2C(O)—O-alkyl, —CH2C(O)NH2, —CH2C(O)—NHalkyl or —CH2C(O)—N(alkyl)2; R19is optionally substituted phenyl, heteroaryl or naphthyl, cycloalkyl, cycloalkylalkyl or alkoxyalkyl; and R5, R13, R14, R15and R16are hydrogen or alkyl for the treatment of HIV, solid organ transplant rejection, graft v. host disease, arthritis, rheumatoid arthritis, inflammatory bowel disease, atopic dermatitis, psoriasis, asthma, allergies or multiple sclerosis is disclosed, as well as novel compounds, pharmaceutical compositions comprising them, and the combination of CCR5 antagonists of the invention in combination with antiviral agents useful in the treatment of HIV or agents useful in the treatment of inflammatory diseases.
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-
- Epothilone analogs
-
Novel analogs of epothilone A, epothilone B, and epothilone C are synthesized by Stille coupling thazole-stannanes to macrolactone intermediates. The synthetic epothilone analogs selectively prevent mitosis in cancer cells through the induction and stabilization of microtubulin assembly. Selected synthetic epothilone analogs are demonstrated to have greater bioactivity than their corresponding native compound.
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-
- A structure-reactivity correlation with three slopes in the elimination kinetics of 2-substituted ethyl N,N-dimethyl-carbamates in the gas phase
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The elimination kinetics of 17 2-substituted ethyl N,N-dimethylcarbamates in the gas phase were determined in the temperature range of 269.5-420.2°C and the pressure range of 24-186 Torr. The reactions in a static system and in the presence of a free radical inhibitor are homogeneous and unimolecular and follow a first-order rate law. The kinetics and thermodynamic parameters are described. The use of several structure-reactivity relationship methods meaningless results, except for Taft σ* values. Three good slopes are originated at σ*(CH3) = 0.00. Slope a: the 2-substituted alkyl groups gave a good straight line when log (k/kCH3) vs σ* values (ρ* = - 1.94 ± 0.30, r = 0.977 at 360°C) were plotted. Slope b: Polar2 substituents gave an approximate straight line with ρ* = - 0.12 ± 0.02, r = 0.936 at 360°C. Slope c:the correlation of multiple bonded and electron-withdrawing substituents interposed by a methylene group at the 2-position of ethyl N,N-dimethylcarbamate was found to give a very good straight line wirh ρ* = 0.49 ± 0.02, r = 0.991 at 360°C. Mechanisms are suggested on the basis of these relationships. The point position of the substituents phenyl (C6H5) and isopropenyl [CH2=C(CH3)] at the 2-position was found to fall far above the three slopes of the lines. These results are interpreted in terms of neighboring group participation of these substituents in the elimination process of the carbamates. However, the acidity of the benzylic and allylic Cβ-H bond for a six-membered cyclic transition state may not be ignored. Copyright
- Chuchani, Gabriel,Nunnez, Oswaldo,Marcano, Norka,Napolitano, Suvighey,Rodriguez, Henry,Dominguez, Marianella,Ascanio, Judany,Rotinov, Alexandra,Dominguez, Rosa M.,Herize, Armando
-
p. 146 - 158
(2007/10/03)
-
- Synthetic techniques and intermediates for polyhydroxy, dienyl lactone derivatives
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Synthetic methods for lactone-containing compounds such as the discodermolides are provided, as are compounds which mimic the chemical and/or biological activity thereof, and methods and intermediates useful in their preparation.
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-
-
- Estrogen agonists/antagonists
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Compounds of this formula are useful for treating or preventing, obesity, breast cancer, osteoporosis, endometriosis, cardiovascular disease and prostatic disease.
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-
-
- Estrogen agonists/antagonists
-
Compounds of formula A inhibit bone resorption and bone turnover, prevent bone loss, preserve bone strength and decrease serum cholesterol without causing prostate hypertrophy in male mammals: and E and B are selected from CH and N. R4 is H, OH, F or Cl.
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-
-
- Synthetic techniques and intermediates for polyhydroxy, dienyl lactone derivatives
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Synthetic methods for lactone-containing compounds such as the discodermolides are provided, as are compounds which mimic the chemical and/or biological activity thereof, and methods and intermediates useful in their preparation.
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-
- Catalytic reaction of methane with CBrF3
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The catalytic reaction of CH4 with CBrF3 over Co, Cu and Mn ZSM-5 zeolites is described; major products (at low temperatures) are those expected for simple hydrodebromination: CH3Br and CHF3.
- Li, Kai,Kennedy, Eric,Dlugogorski, Bogdan,Howe, Russell
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p. 709 - 710
(2007/10/03)
-
- Electrophilic bromination of ethylene and ethylene-d4. A combined experimental and theoretical study
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The deuterium kinetic isotope effect (dkie) for the electrophilic bromination of ethylene-h4 and ethylene-d4 in methanol and dichloroethane (DCE) at 25 °C has been determined using mass spectrometry. The dkie's are inverse, that in methanol being k(H)/k(D) = 0.664 ± 0.050 and that in DCE being k(H)/k(D) = 0.572 ± 0.048. A product study of the bromination of trans-ethylene-d2 in dichloroethane indicates that the addition is trans. Computations of the expected equilibrium deuterium isotope effect (EIE) for the process C2H4 + Br+ ? C2H4-Br+ using density functional theory indicate that the EIE is also inverse at K(H)/K(D) = 0.63. Detailed analyses of the molar partition functions and the zero-point energies for the various vibrational modes in the ground and ion states indicate that the major contributor to the EIE is the creation of a new mode in the ion, termed the CH2-symmetric twist, that arises from the loss of the rotational freedom about the C-C axis in ethylene. In the absence of this new mode, the computed EIE is normal, K(H)/K(D) = 1.12. The computations also indicate that the ion state undergoes very little rehybridization of the carbons, the sum of the H- C-H and H-C-C angles at each carbon being 357.3°. A discussion is presented concerning the detailed sequence of events contributing to the reaction mechanism in both solvents and how each of these might contribute to the dkie.
- Koerner, Terry,Brown,Gainsforth,Klobukowski
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p. 5628 - 5636
(2007/10/03)
-
- Synthetic techniques and intermediates for polyhydroxy, dienyl lactones and mimics thereof
-
Synthetic methods for lactone-containing compounds such as the discodermolides are provided, as are compounds which mimic the chemical and/or biological activity thereof, and methods and intermediates useful in their preparation.
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-
- Method for effecting vasodilation with (1,5-inter)aryl prostaglandin derivatives
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The present invention provides a method of effecting vasodilation, comprising: administering to a warm blooded animal in need of such treatment, an effective amount of a (1,5-inter) aryl prostaglandin derivative represented by the Formula I STR1 wherein n is 0 or an integer of from 1 to 6, R is selected from the group of radicals represented by the formulae: wherein R' is hydrogen or a lower alkyl radical having from one to six carbon atoms; R is hydrogen or an acyl radical having the formula (CO)R' wherein R' is a saturated or unsaturated acyclic hydrocarbon radical having from 1 to about 10 carbon atoms, or --(CH2)m R wherein m is 0 or an integer of from 1 to 6 and R is an aliphatic ring having from 3 to 7 carbon atoms or an aryl group, e.g. phenyl, or a heteroaryl group, e.g. thienyl, furanyl or pyridyl, and preferably R' is a lower alkyl group having from 1 to 6 carbon atoms; the hatched triangular segments represent alpha oriented bonds, the solid triangular segments represent beta oriented bonds and the wavy segments represent bonds that may be in either the cis or trans orientation. More preferably said (1,5 inter) aryl prostaglandin derivative is a compound represented by Formula II STR2 Most preferably, said (1,5-inter) aryl prostaglandin derivative is a compound of Formula II wherein R is CO2 R', R' is hydrogen and n is 0.
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- Anti-viral compounds
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Certain vinyl acetylene benzimidazole compounds which inhibit the growth of picornaviruses, such as rhinoviruses, enteroviruses, cardioviruses, polioviruses, coxsackieviruses of the A and B groups, echo virus and Mengo virus.
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-
- 5-substitued-6-cyclic-5,6,7,8-tetrahydronaphthalen2-ol compounds which are useful for treating osteoporosis
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Compounds of this formula STR1 are useful for treating or preventing, obesity, breast cancer, osteoporosis, endometriosis, cardiovascular disease and prostatic disease.
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-
- Photochemistry of Hydrogen Bromide-Acetylene Complexes in Solid Krypton
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Hydrogen-bonded complexes between HBr and acetylene in inert gas matrices were subjected to medium-pressure Hg lamp photolysis at 12 K.For HBr-acetylene, the major product was bromoacetylene, while vinyl bromide was present in trace amounts.When HBr-perdeuterioacetylene and DBr-acetylene complexes were photolyzed, bromoacetylene, deuteriobromoacetylene, and the hydrogen exchange product, DBr(HBr)-C2HD, were the primary products.Partially deuterated vinyl bromides were present in trace amounts.In HBr-perdeuterioacetylene, the only isomer observed was cis-CDBr=CHD.In DBr-acetylene, both cis- and trans-CHBr=CHD were observed.In neither experiment was the 1,1-addition product formed.The results are interpreted in terms of the supramolecule model of complex photochemistry put forth by Abrash and Pimentel.
- Abrash, Samuel A.,Carr, Celia M.,McMahon, Michael T.,Zehner, Robert W.
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p. 11909 - 11917
(2007/10/02)
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- Kinetic studies of the N-Alkylation of secondary amines with 1, 2-dichloroethane
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The reaction of 1,2-dichloroethane with 2-(ethylamino)ethanol or diethylamine have been investigated in several solvents from 51 to 80°C. A reaction mechanism has been proposed where 1, 2-dichloroethane reacts with the secondary amines in both bimolecular substitution (SN 2) and elimination (E2) reactions; the substitution product is rapidly converted in an aziridinium ion and undergoes a consecutive reaction with the starting amine to give a tetrasubstituted ethylenediamine. The rate constants as well as the activation energies of these reactions have been determined.
- Yang,Thyrion
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p. 309 - 315
(2007/10/03)
-
- Cyclization of acetylenic alkyllithiums
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The scope and limitations of cyclization reactions involving acetylenic alkyllithiums, which were prepared at-78 °C by lithium-iodine exchange between the corresponding iodide and tert-butyllithium in a solution of n-pentane-diethyl ether (3:2 by volume), have been investigated. 4-Pentynyllithiums, 5-hexynyllithiums, and 6-heptynyllithiums bearing a phenyl or trimethylsilyl substituent on the triple bond undergo regiospecific exo-dig cyclization to give 4-, 5-, and 6-membered rings, respectively, bearing an exocyclic lithiomethylene moiety. Cyclization of the analogous alkyl-substituted acetylenic alkyllithiums seems to be confined to the 5-exo mode. The vinyllithium products of the cyclizations may be trapped by reaction with electrophiles to afford functionalized cycloalkylidene derivatives in good yield. The cyclization reactions were found to be highly stereoselective: intramolecular addition of the C-Li unit to the triple bond to produce 4- or 5-membered rings proceeds in a syn fashion to generate isomerically pure exocyclic vinyllithiums that may be functionalized to give stereoisomerically pure products. At the higher temperatures needed to effect cyclization of 6-heptynyllithiums, the initially formed (Z)-vinyllithium intermediate is isomerized to the more stable E-isomer which, when trapped with an electrophile, affords stereoisomerically pure product formally derived from anti addition to the triple bond.
- Bailey, William F.,Ovaska, Timo V.
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p. 3080 - 3090
(2007/10/02)
-
- Kinetics of the Reactions of Unsaturated Hydrocarbon Free Radicals (Vinyl, Propargyl, and Allyl) with Molecular Bromine
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The kinetics of the reactions of three unsaturated free radicals (vinyl, propargyl, and allyl) with molecular bromine have been studied by using a tubular reactor coupled to a photoionization mass spectrometer.The radicals were homogeneously generated by the pulsed photolysis of precursor molecules at 193 nm.The subsequent decays of the radical concentrations were monitored in time-resolved experiments as a function of Br2 concentration to obtain the rate constants of these Br-atom metathesis reactions.Rate constants were measured as a function of temperature to obtain Arrhenius parameters.The following rate constant expressions were obtained (units of the preexponential factor are cm3 molecule-1 s-1 and activation energies are kJ mol-1; the temperature range covered in each study is also indicated): C2H3 + Br2 , C3H3 + Br2 , and C3H5 +/- Br2 .The kinetics of R + Br2 reactions is reviewed, and the factors governing the reactivity of polyatomic free radicals in R + Br2 reactions are discussed.
- Timonen, R. S.,Seetula, J. A.,Gutman, D.
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p. 8217 - 8221
(2007/10/02)
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- The synthesis of -substituted bromoalkanes and their conversion into Grignard reagents
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Reaction of the nitroxide (CF3)2NO(.) (1) with the bromoalkanes RBr (R = Me, Et and Prn) (1:1 molar ratio) gives the compounds (CF3)2NOCH2Br (4a) (69percent), (CF3)2NOCHBrMe (4b) (93percent) + (CF3)2NOCHBrCH2ON(CF3)2 (6) (6percent) and (CF3)2NOCHBrEt (4c) (16percent) + (CF3)2NOCHMeCH2Br (7) (76percent) + (CF3)2NOCH2CHBrMe (8) (3percent), respectively, together with the hydroxylamine (CF3)2NOH (3).Treatment of the sodium salt (CF3)2NONa (2) with the dibromoalkanes Br(CH2)nBr (n = 2 and 3) (1:1 molar ratio) in diglyme affords mixtures of elimination and substitution products, i.e.H2C=CHBr + (CF3)2NOCH2CH2Br (9a) + (CF3)2NOCH2CH2ON(CF3)2 (10a) (ratio 21:39:7) and (CF3)2NOCH2CH=CH2 (12) + (CF3)2NO(CH2)3Br (9b) + (CF3)2NO(CH2)3ON(CF3)2 (10b) (ratio 22:43:9).The α-substituted compounds 4a and 4b do not form Grignard reagents in diethyl ether, those formed from the β-substituted compounds 7 and 9a undergo elimination to give propene and ethene respectively, while that produced from the γ-substituted compound 9b is stable at room temperature and reacts with the chlorosilane MeSiCl3 to afford the compound (CF3)2NO(CH2)3SiCl2Me (20) (53percent).
- Ducker, Graham E.,Tipping, Anthony E.
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p. 133 - 138
(2007/10/02)
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- Time-Resolved Observation of Vibrationally Excited 1,3-Butadiene in Laser Induced Photolysis of Bromocyclobutane and Cyclohexene
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The pulsed CO2 laser induced SF6 sensitized photodissociation of bromocyclobutane (BCB) and cyclohexene (CHN) is investigated.BCB has two dissociation channels from its ground electronic state, HBr elimination yielding 1,3-butadiene is the major channel (>90percent) whereas, the ring cleavage producing vinyl bromide and ethylene is the minor one.The time-resolved formation of 1,3-butadiene is monitored by UV absorption from which unimolecular rate constants for BCB and CHN dissociation are found to be 8*105 s-1 and 1*106 s-1, respectively.A red-shift of 38 nm and 50 nm observed in the UV spectra of butadiene produced respectively from BCB and CHN, suggests that vibrationally hot butadiene molecules are formed.The effects of laser fluence, pressure of SF6 and the no. of laser pulses on dissociation yield and the branching ratio in BCB are also investigated.
- Kumar, Awadhesh,Vatsa, Rajesh Kumar,Chowdhury, Pradyot Kumar,Rama Rao, Kuchimanchi Venkata Subba,Mittal, Jai Pal
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p. 1603 - 1607
(2007/10/02)
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- Oxygenated alicyclic compounds and their use in perfumery
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A compound of formula STR1 wherein R1 represents a hydrogen atom or a saturated, linear or branched, alkyl radical, having from 1 to 4 carbon atoms, and R2 designates a lower alkyl radical, saturated or unsaturated, linear or branched; or any mixture containing a predominant amount of said compound (I), together with its isomer of formula STR2 wherein R1 and R2 are defined as above. Compounds (I) and their mixtures mentioned above develop odor notes of the woody-amber type and are therefore used as perfuming ingredients for the preparation of perfuming compositions and perfumed articles. A process for the preparation of compounds (I) and their mixtures is disclosed.
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- Photolysis of alkylhalodiazirines: Two pathways for vinyl halide formation
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Photoacoustic calorimetry and product studios on the photochemical decomposition of methylhalodiazirines indicate two pathways for the formation of vinyl halides: 1) a [1,2] intramolecular hydrogen shift of the initially formed methylhalocarbene, 2) an excited state pathway which circumvents the ground state carbene. Results suggest that carbene/olefin or carbene/alcohol complexes are not involved in vinyl halide formation.
- La Villa, Joseph A.,Goodman, Joshua L.
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p. 5109 - 5112
(2007/10/02)
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- Gas-Phase Addition of the Vinyl Cation to Hydrogen and Methane. A Nuclear Decay Study
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A nuclear technique based on the spontaneous decay of multitritiated precursors that allows the generation of free carbenium ions of exactly the same nature in different enviroments has been employed for generating the labeled vinyl cation (C2X3(1+), X = H,T) from multitritiated ethylene and for investigating its reactivity toward hydrogen and methane at pressures ranging from 60 to 720 Torr.Kinetic data for the addition of C2X3(1+) to H2 and CH4 and the ensuing product distributions are obtained by intercepting the ionic species with different gaseous nucleophiles, i.e., 1,4-dibromobutane, benzene, and methanol, and by isolating the corr esponding neutral end products.The results are consistent with the intermediacy of the vinyl cation, formed by the β(1-) transition with a limited excess of vibrational energy, which insert into the ?-bonds of H2 and CH4 yielding respectively C2H5(1+) and sC3H7(1+) ions.The experiments provide no evidence for the occurrence of alternative C3H7(1+) structures, i.e., protonated cyclopropane, from the C2X3(1+) attack on CH4.At CH4 pressures below 200 Torr, a fraction of the C3H7(1+) adducts fragments diretly into allyl cations and H2.A definition of the C2X3(1+) + H2(or CH4) addittion and fragmentation mechanism is obtained by comparison of the present data with those arisisng from previous experimental studies based on different approaches (i.e., radiolysis, ICR, SIFT, HMPS, etc.) and with those of ab initio calculations.
- Fornarini, Simonetta,Speranza, Maurizio
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p. 2154 - 2160
(2007/10/02)
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- Photodecomposition of Gaseous Bromoethane at 163.4 nm
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The 163.4-nm photolysis of gaseous C2H5Br has been investigated at 298 K over the pressure range 2-100 torr, using a bromine lamp.The effects of additives, N2,CF4, and NO, were also studied.In the pure system the observed reaction products and their respective quantum yields are C2H4 (ca.0.36), C2H6 (0.42-0.79), C2H3Br(0.1-0.24), CH3CHBr2 (0.24-0.32) and n-C4H10 (0.01), most yields increasing with substrate pressure.An opposite trend is observed with increasing pressure of inert gases.The addition of NO as a radical scavenger completely supresses the formation of C2H6, C2H3Br, CH3CHBr2, and n-C4H10, and partially reduces the yield of C2H4.The results are interpreted in terms of the initial formation of two electronically excited states which are linked by way of a pressure dependence, one of which yields C2H4 by molecular elimination of HBr, while the second decomposes by carbon-halogen bond fission.The kinetics of the secondary process are discussed in some detail.
- Jung, Kyung-Hoon,Choi, Young Sik,Yoo, Hee Soo,Tschuikow-Roux, E.
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p. 1816 - 1822
(2007/10/02)
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- Process for the preparation of fluorinated nitroalkanes
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In the conjugated nitrofluorination of an olefin by reacting an olefin of the formula STR1 in which R1, R2, R3 and R4 each independently is hydrogen, fluorine, chlorine, bromine, alkyl, halogenoalkyl or cycloalkyl, or R2 and R4 together are an alkylene radical of 3 to 6 carbon atoms, with hydrogen fluoride and nitric acid to produce an α-fluorinated nitroalkane of the formula STR2 the improvement which comprises effecting the reaction in a vessel protected against corrosion employing about 1 to 1.1 mols of hydrogen fluoride and about 1 to 2 mols of nitric acid per mol of olefin. The process uses much less HF than heretofore and the products are useful intermediates in making herbicides. Some of the products are new.
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- Photolysis of 3-Bromo-3-methyldiazirine
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The photolysis at 354 nm of 3-bromo-3-methyldiazirine in gas phase has been studied.After a careful search of the various possibilities we have found that all available evidence points toward the intermediary formation of hot vinyl bromide, presumably via isomerization of the corresponding carbene.Its unimolecular decomposition can take place by two different paths: one is the molecular detachment of HBr and the other the radical scission of the C-Br bond.This last way of radical formation is responsible for the apparently confusing experimental data.According to our result the activation energy for the radical decomposition is closer to that of the molecular detachment than previously thought.
- Crespo, Maria T.,Figuera, Juan M.,Rodriguez, Juan C.,Utrilla, Roberto Martinez
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p. 5790 - 5796
(2007/10/02)
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- Synthesis of some 1,2-Dihalogenonorbornanes
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The synthesis of 1,2exo-dibromo-norbornane as well as the preparation of the configurational isomers of 2-bromo-1-iodo- and 2-chloro-1-iodo-norbornane are described.
- Krebs, Ernst-Peter,Keese, Reinhart
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p. 2029 - 2041
(2007/10/02)
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- Thermocatalytic Reactions of 1,1-Bromochloroethane
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The thermocatalytic reactions of 1,1-bromochloroethane have been investigated and the thermodynamic characteristics (ΔH0T and ΔS0T) of the disproportionation and dehydrohalogenation reactions have been obtained.The thermodynamic functions (ΔH0f and S0) of 1,1-bromochloroethane have been estimated and the deviation of the enthalpy of formation from additivity owing to the Cl-Br mutual influence in the gem-positions has been determined.
- Bushneva, L. I.,Levanova, S. V.,Rodova, R. M.,Rozhnov, A. M.
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p. 1403 - 1404
(2007/10/02)
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