- Degradation pathways of trichloroethylene and 1,1,1-trichloroethane by Mycobacterium sp. TA27
-
We analyzed the kinetics and metabolic pathways of trichloroethylene and 1,1,1-trichloroethane degradation by the ethane-utilizing Mycobacterium sp. TA27. The apparent Vmax and Km of trichloroethylene were 9.8 nmol min-1 m
- Hashimoto, Akiko,Iwasaki, Kazuhiro,Nakasugi, Naou,Nakajima, Mutsuyasu,Yagi, Osami
-
-
Read Online
- Laser Photolysis/Laser-Induced Fluorescence Studies of the Reaction of OH with 1,1,1-Trichloroethane over an Extended Temperature Range
-
Absolute rate coefficients are determined for the gas-phase reaction of OH radicals with 1,1,1-trichloroethane over an extended temperature range.Employing a laser photolysis/laser-induced fluorescence technique, experiments were conducted with a flow system at a total pressure of 740 +/- 10 Torr using He as diluent and carrier gas.The rate coefficients, obtained over the temperature range 298-761 K, exhibited pronounced non-Arrhenius behavior and were best described by the modified Arrhenius equation k(T)=(3.95 +/- 0.78) x 10-13(T/300)2.08exp cm3 molecule-1 s-1.Comparison of the data with numerous lower temperature measurements is presented.The temperature dependence of the data is compared with empirical and transition-state model calculations.The reactivity of this compound with OH compared to other chlorinated ethanes at both lower and higher reaction temperatures is presented and discussed.
- Jiang, Zhen,Taylor, Philip H.,Dellinger, Barry
-
-
Read Online
- Laser Photolysis/Laser-Induced Fluorescence Studies of the Reaction of OH with 1,1-Dichloroethane over an Extended Temperature Range
-
Absolute rate coefficients are determined for the gas-phase reaction of OH radicals with 1,1-dichloroethane over an extended temperature range using a laser photolysis/laser-induced fluorescence technique.Experiments were performed in a flow system at a total pressure of 740 +/- 10 Torr using He as diluent and carrier gas.The rate coefficients, obtained over the temperature range 294-800 K, exhibited pronounced non-Arrhenius behavior and were best described by the modified Arrhenius equation k(T)=(8.29 +/- 0.36) x 10-14(T/300)2.67exp cm3 molecule-1 s-1.Comparison of the data with one previous room-temperature measurement is presented.The temperature dependence of the data is compared with empirical and transition-state model calculations.The influence of C-H bond energy and Cl substitution is discussed.
- Jiang, Zhen,Taylor, Philip H.,Dellinger, Barry
-
-
Read Online
- Kinetics of the Reactions of OH with C2H6, CH3CCl3, CH2ClCHCl2, CH2ClCClF2, and CH2FCF3
-
The rate constants of the five H-abstraction reactions are measured from about 250 to 470 K by using the discharge-flow technique.Arrhenius parameters, three-parameter fits, and modified A and E values centered at 300 K are obtained.As in earlier papers on substituted methanes, Ath300 is calculated by thermochemical transition-state theory and compared with Aexp300, giving good agreement, on average, for a C-H-O bond angle of 150 deg.Three-parameter fits are reexamined for the ten methane reactions, their usefulness is discussed, and the dependence of Aexp300 on n, the temperature exponent, is calculated.Consequently, it is suggested that fitting routines be guided by theoretical considerations.
- Jeong, Kyu-Man,Hsu, Kuang-Jung,Jeffries, J. B.,Kaufman, Frederick
-
-
Read Online
- High utility of Saccharomyces cerevisiae harboring rat liver cytochrome P450 1A2 cDNA in haloethanes dehalogenations
-
Yeast harboring rat liver P450 1A2 efficiently degraded trichloroethylene, pentachloroethane and hexachloroethane. Since liver P450s catalyze degradation of thousands of chemicals, this method is promising for chemical-directed degradation of environmental pollutants.
- Yanagita, Kazutaka,Sagami, Ikuko,Shimizu, Toru
-
-
Read Online
- Microwave-assisted Cannizzaro reaction—Optimisation of reaction conditions
-
The microwave-assisted Cannizzaro reaction was studied in order to develop fully reproducible synthetic protocols for transformation of aldehydes to carboxylic acid and alcohols. Optimised were the following process parameters: power, temperature, and time. Aromatic, heteroaromatic and aliphatic aldehydes were used in the studies. It was found that furfural, thiophene-2-carbaldehyde, pyridinecarboxaldehyde and aromatic aldehydes react under mild conditions, while 1-methyl-pyrrole-2-carboxaldehyde derivatives and aliphatic aldehydes require more drastic reaction conditions and a longer exposure time to microwave radiation.
- Janczewski, ?ukasz,Walczak, Ma?gorzata,Fr?czyk, Justyna,Kamiński, Zbigniew J.,Kolesińska, Beata
-
supporting information
p. 3290 - 3300
(2019/11/05)
-
- A DMAP-catalyzed approach to the industrial-scale preparation of N -6-demethylated 9,10-dihydrolysergic acid methyl ester: A key cabergoline and pergolide precursor
-
A scalable new approach for the preparation of N-6-demethylated 9,10-dihydrolysergic acid methyl ester using 2,2,2-trichloroethyl chloroformate was developed. A key discovery that enabled the efficient and industrial-scalable process is linked to the rigorous extrusion of water in the reaction system and application of an organic catalyst such as 4-(N,N-dimethylamino)pyridine (DMAP) instead of the alkali metal bicarbonate additives. Namely, in the previously known process, the concomitant presence of bicarbonates and traces of water triggers side reaction cycles that produce and accumulate hydrochloric acid and water. The former slows down the reaction. Moreover, these cycles cause the formation of multiple carbonate and alcohol-type side products to a significant extent that provide a low-quality N-6-demethylated product. All of these shortcomings are circumvented by the application of DMAP as a catalyst and the use of a reaction medium free of water. This approach allows operation on an industrial scale (51 kg batch) with higher yields, shorter reaction times, and improved product quality.
- asar, Zdenko,Mesar, Toma
-
supporting information
p. 378 - 385
(2015/04/21)
-
- Introducing a mixed-valent dirhodium(ii,iii) catalyst with increased stability in C-H amination
-
A new mixed-valent Rh2II,III dimer, [Rh 2(espn)2Cl] (espn2- = α,α, α′,α′-tetramethyl-1,3-benzenedipropanamidate), is reported. This compound readily dissociates Cl- at low concentrations in solution to form the active [Rh2(espn)2]+ catalyst, which performs intramolecular C-H amination with TONs > 1400. This work expands the scope of Rh2II,III dimers to nitrenoid chemistry.
- Kornecki, Katherine P.,Berry, John F.
-
p. 12097 - 12099
(2013/01/16)
-
- Practical and chemoselective reduction of acyl chloride to alcohol by borohydride in aqueous dichloromethane
-
A simple methodology for the reduction of acid chlorides to their corresponding alcohols has been developed. Various carboxylic acids were converted to alcohols in excellent yields using NaBH4-K2CO3 in a mixed solvent system of dichloromethane and water (1:1) in the presence of a phase-transfer catalyst at low temperature. The importance of the work is its simplicity, selectivity, excellent yield, and very short reaction time. This new reduction condition has proved to be an excellent chemoselective method for a range of acid chlorides in the presence of various functional groups.
- Rajan, Ramya,Badgujar, Sachin,Kaur, Kamaljit,Malpani, Yashwardhan,Kanjilal, Pranab R.
-
experimental part
p. 2897 - 2907
(2010/11/18)
-
- 1,2-H shift in copper-chlorocarbenoid intermediate during CuCl/bpy-promoted stereoselective dechlorination of 2,2,2-trichloroethyl alkyl ethers to (Z)-1-alkoxy-2-chloroethenes
-
(Chemical Equation Presented) Reaction of 2,2,2-trichloroethyl alkyl ethers with 2 molar equiv of CuCl/bpy in refluxing DCE yielded (Z)-1-alkoxy-2- chloroethenes stereoselectively as the major product via 1,2-H shift in copper-chlorocarbenoid intermediate. 2,2,2-Trichloroethyl carboxylates undergo a radical 1,2-acyloxy shift under similar conditions.
- Ram, Ram N.,Manoj
-
supporting information; experimental part
p. 2243 - 2246
(2009/05/11)
-
- Enzymatic removal of carboxyl protecting groups. III. Fast removal of allyl and chloroethyl esters by Bacillus subtilis esterase (BS2)
-
(Chemical Equation Presented) An esterase from Bacillus subtilis (BS2) allows the fast and selective removal of allyl, 2-chloroethyl, and 2,2,2-chloroethyl esters under mild conditions in high yields. In addition, BS2 easily hydrolyzes phenacyl esters, while the hydrolysis of sterically hindered diphenylmethyl esters is slow, requiring longer reaction time and higher enzyme/substrate ratio.
- Fotakopoulou, Irene,Barbayianni, Efrosini,Constantinou-Kokotou, Violetta,Bornscheuer, Uwe T.,Kokotos, George
-
p. 782 - 786
(2007/10/03)
-
- Benzoxazinoes/benzothiazinones as serine protease inhibitors
-
This invention discloses benzoxazinone and benzothiazinone compounds which display inhibitory effects on serine proteases such as factor Xa, thrombin, and/or factor VIIa. The invention also discloses pharmaceutically acceptable salts of the compounds, pharmaceutically acceptable compositions comprising the compounds or their salts, and methods of using them as therapeutic agents for treating or preventing disease states in mammals characterized by abnornal thrombosis.
- -
-
-
- A Convenient Method for Protection and Deprotection of Alcohols and Phenols as Alkylsilyl Ethers Catalyzed by Iodine under Microwave Irradiation
-
Irradiation of alcohols or phenols with tert-butyldimethylsilyl chloride (TBDMSCl) or trimethylsilyl chloride (TMSCl) in presence of catalytic amount (20 mol%) of iodine in a microwave oven for 2 min gives the corresponding silyl ethers in excellent yield. Iodine in methanol deprotects the silyl ether into its parent alcohol or phenol under similar reaction conditions.
- Saxena, Ira,Deka, Nabajyoti,Sarma, Jadab C.,Tsuboi, Sadao
-
p. 4185 - 4191
(2007/10/03)
-
- The photolytic and hydrolytic lability of sisyl (Si(SiMe3)3) ethers, an alcohol protecting group
-
The tris(trimethylsilyl)silyl (sisyl) group is a photolabile protecting group for primary and secondary alcohols. Sisyl (tris(trimethylsilyl)silyl) ethers 2b-11b of a number of primary and secondary alcohols 2a-11a were prepared in yields ranging from 70-97%. The resulting silyl ethers were stable to aqueous bases, Grignard reagents and Wittig reagents as would be expected for bulky alkoxysilanes. They were also stable to selected fluoride salts including CsF. The sisyl ethers could be cleaved using photolysis at 254 nm in under 30 minutes to give the starting alcohols in yields ranging from 62-95%. The photolytic behaviour of sisyl ethers was examined in more detail using 2,3-dimethyl-1,3-butadiene as a silylene trap. The regiochemistry of the oligosilane fragmentation to silylenes was shown to be dependent upon the alkoxy group. The hydrolytic stability of three was compared with the analogous t-butyldimethylsilyl ethers. The relative stability of the two silyl groups can be altered by choice of solvent: in acetic acid/water the ease of hydrolysis followed the order ROSi(SiMe3)3 > ROSiMe2t-Bu; the inverse order was observed in CDCl3 using p-TsOH·H2O. Pseudo-first-order rate constants for the acidic hydrolysis of primary, benzylic, and secondary sisyl ether in AcOH/THF/H2O were determined to be 3.74 x 10-2 s-1, 1.94 x 10-2 s-1, and 1.30 x 10-2 s-1, respectively. The analogous rate constants for the TBS ethers were determined to be 6.04 x 10-3 s-1, 3.53 x 10-3 s-1, and 3.49 x 10-3 s-1, respectively.
- Brook,Balduzzi,Mohamed,Gottardo
-
p. 10027 - 10040
(2007/10/03)
-
- The mechanism of the metal ion promoted cleavage of RNa phosphodiester bonds involves a general acid catalysis by the metal aquo ion on the departure of the leaving group
-
A series of uridine 3′-alkyl phosphates and 3′-aryl phosphates were synthesised and their cleavage was studied in the presence of Zn2+ aquo ions. A βlg value was determined for the Zn2+ promoted cleavage of both types of compounds. Comparison of the results obtained to those reported previously for the cleavage of the same substrates in the absence of metal ion catalysts suggests that the alkyl leaving group departs as an alcohol in the presence of metal ion catalysts. Furthermore, metal ion catalysts seem to enhance the departure. The aryl leaving group, in contrast, departs as an oxyanion.
- Mikkola, Satu,Stenman, Eeva,Nurmi, Kirsi,Yousefi-Salakdeh, Esmail,Stroemberg, Roger,Loennberg, Harri
-
p. 1619 - 1625
(2007/10/03)
-
- Metabolism of trichloroethylene and chloral hydrate by the Japanese medaka (Oryzias latipes) in vitro
-
Trichloroethylene (TRI), a common groundwater contaminant, is readily metabolized by mammals to produce chloral hydrate (CH), trichloroacetic acid (TCA), and trichloroethanol (TCOH). Cytochrome P450 (CYP) and other enzymes are responsible for formation of these metabolites, which are implicated in TRI's toxicity and carcinogenicity. To establish the validity of the Japanese medaka (Oryzias latipes) as an alternate test species for TRI, we examined the metabolism of TRI and CH, as well as CYP expression, in medaka liver preparations. Trichloroethylene was incubated with medaka microsomal protein, and metabolites were extracted and analyzed using gas chromatography. Microsome-mediated metabolism of TRI was observed, and a K(m) value for TRI oxidation of 540 μM and a V(max) value of 213 pmol/min·mg-1 protein were obtained. Conversion of TRI to CH, TCA, and TCOH was found with medaka hepatic subcellular fractions. In addition, a sex difference in hepatic microsomal TRI metabolism, specific CYP content, and ethoxyresorufin O- deethylase activity was noted. The lower specific activity of preparations from the livers of female medaka is compensated for by increased total protein in the larger liver mass of the female. Immunochemical analysis showed that CYP1A was readily detectable in medaka liver, but CYP2E1 was present at very low levels. These data suggest that TRI metabolism in medaka liver preparations mimics that observed in mammalian systems and supports their use as an alternative test species in the evaluation of the toxicity of TRI.
- Lipscomb, John C.,Confer, Patricia D.,Miller, Michael R.,Stamm, Steven C.,Snawder, John E.,Bandiera, Stelvio M.
-
p. 325 - 332
(2007/10/03)
-
- Condensed benzazepine derivative and pharmaceutical composition thereof
-
This invention relates to nitrogen-containing aromatic 5-membered ring-condensed benzazepine derivatives represented by the general formula (I) STR1 (symbols in the formula have the following meanings; ring B: a nitrogen-containing aromatic 5-membered ring having at least 1 nitrogen atom and optionally one oxygen or sulfur atom, which may optionally have substituent(s), R1 and R2 : these may be the same or different from each other and each represents a hydrogen atom, a halogen atom, a lower alkyl group, an amino group which may optionally be substituted by lower alkyl group(s), or a lower alkoxy group, A: a single bond; a group represented by the formula n: 0 or an integer of from 1 to 3, R3 and R4 : these may be the same or different from each other and each represents a hydrogen atom, a lower alkyl group (provided that R3 and R4 may together form a lower alkylene group having 2 to 7 carbon atoms), and ring C: a benzene ring which may optionally have substituent(s)) and salts thereof; to pharmaceutical compositions which contain these compounds as an active ingredient and to intermediates which are useful in synthesizing these compounds. The compounds of this invention are useful as arginine vasopressin antagonists.
- -
-
-
- The sisyl (tris(Trimethylsilyl)silyl) group: A fluoride resistant, photolabile alcohol protecting group
-
The use of the tris(trimethylsilyl)silyl (sisyl) group as a photolabile protecting group for primary and secondary alcohols was demonstrated. Sisyl ethers of a number of alcohols (yields 70-97%) were stable to many synthetic protocols, but could be deprotected using photolysis to give the starting alcohols (yields 62-95%).
- Brook, Michael A.,Gottardo, Christine,Balduzzi, Sonya,Mohamed, Mustafa
-
p. 6997 - 7000
(2007/10/03)
-
- Zirconium alkoxide catalyzed Oppenauer oxidation using chloral as the hydride acceptor
-
A new variation of the Oppenauer oxidation is presented with chloral as the hydride acceptor and Zr(O-t-Bu)4 or, for highly reactive carbonyl products, the heterogeneous system SiO2/Zr(O-n-Pr)(x), as the catalyst. The reaction proceeds under mild conditions (20°C) with a substoichiometric amount of Zr(O-t-Bu)4 (usually 20%). Primary and secondary allyl alcohols are converted in high yields to the corresponding carbonyl compounds.
- Krohn, Karsten,Knauer, Birgit,Kuepke, Jochen,Seebach, Dieter,Beck, Albert K.,Hayakawa, Michyay
-
p. 1341 - 1344
(2007/10/03)
-
- Cyclization-Activated Prodrugs: N-(Substituted 2-hydroxyphenyl and 2-hydroxypropyl)carbamates Based on Ring-Opened Derivatives of Active Benzoxazolones and Oxazolidinones as Mutual Prodrugs of Acetaminophen
-
N-(Substituted 2-hydroxyphenyl)- and N-(substituted 2-hydroxypropyl)carbamates based on masked active benzoxazolones (model A) and oxazolidinones (model B), respectively, were synthesized and evaluated as potential drug delivery systems.A series of alkyl and aryl N-(5-chloro-2-hydroxyphenyl)carbamates 1 related to model A was prepared.These are open drugs of the skeletal muscle relaxant chlorzoxazone.The corresponding 4-acetamidophenyl ester named chloracetamol is a mutual prodrug of chloroxazone and acetaminophen.Chlorzacetamol and two other mutual prodrugs of active bezoxazolones and acetaminophen were obtained in a two-step process via condensation of 4-acetamidophenyl 1,2,2,2-tetrachloroethyl carbonate with the appropiate anilines.Based on model B, two mutual prodrugs of acetaminophen and active oxazolidinones (metaxalone and mephenoxalone) were similarly obtained using the appropiate amines.All the carbamate prodrugs prepared were found to release the parent drugs in aqueous (pH 6-11) and plasma (pH 7.4) media.The detailed mechanistic study of prodrugs 1 carried out in aqueous medium at 37 deg C shows a change in the Broensted-type relationship log t1/2 vs pKa of the leaving groups ROH: log t1/2 = 0.46pKa - 3.55 for aryl and trihalogenoethyl esters and log t1/2 = 1.46pKa - 16.03 for alkyl esters.This change is consistent with a cyclization mechanism involving a change in the rate-limiting step from formation of a cyclic tetrahedral intermediate (step k1) to departure of the leaving group ROH (step k2) when the leaving group ability decreases.This mechanism occurs for all the prodrugs related to model A.Regeneration of the parent drugs from mutual prodrugs related to model B takes place by means of a rate-limiting elimination-addition reaction (E1cB mechanism).This affords acetaminophen and the corresponding 2-hydroxypropyl isocyanate intermediates which cyclize at any pH to the corresponding oxazolidinone drugs.As opposed to model A, the rates of hydrolysis of mutual prodrugs of model B clearly exhibit a catalytic role of the plasma.It is concluded from the plasma studies that the carbamate substrates can be enzymatically transformed into potent electrophiles, i.e., isocyanates.In the case of the present study, the prodrugs are 2-hydroxycarbamates for which the propinquity of the hydroxyl residue and the isocyanate group enforces a cyclization reaction.This mechanistic particularity precludes their potential toxicity in terms of potent electrophiles capable of modifying critical macromolecules.
- Vigroux, Alain,Bergon, Michel,Zedde, Chantal
-
p. 3983 - 3994
(2007/10/03)
-
- Hydrolysis of Nitrite Esters: Putative Intermediates in the Biotransformation of Organic Nitrates
-
Study and comparison of the pH-independent hydrolysis of eight alkyl nitrites shows 3-nitroso-1,2-glyceryl dinitrate, a putative intermediate in the biotransformation of glyceryl trinitrate, to be unexpectedly reactive and too labile to be detected as a biotransformation intermediate in aqueous solution, suggesting a role for neighbouring group participation by the β-nitrate group.
- Buckell, Felicity,Hartry, Jeffrey D.,Rajalingam, Umarani,Bennett, Brian M.,Whitney, Ralph A.,Thatcher, Gregory R. J.
-
p. 401 - 404
(2007/10/02)
-
- Rate enhancement of the Candida cylindracea lipase catalysed transesterification in organic solvents: Enzymatic reactions below zero
-
The rate of transesterification reactions of primary and secondary alcohols, catalysed by the lipase from Candida cylindracea in organic solvents, can be accelerated when methoxyacyl is the transacylating group in the transacylating agent.This phenomenon allows efficient transesterifications to be catalysed at temperatures below zero degree.
- Hogan, V F,O'Hagan, D,Sanvoisin, J
-
p. 883 - 885
(2007/10/02)
-
- Kinetics of the Alkaline Hydrolysis of several Alkyl Phenylcarbazates
-
The kinetics in 25percent (v/v) dioxane-water of the alkaline hydrolysis, followed by UV spectrometry, of several alkyl phenylcarbazates (Ar-NH-NHCOOR, with Ar = phenyl, 4-chlorophenyl, 4-fluorophenyl, 3,4-dichlorophenyl and R = methyl, ethyl, propyl, chloroethyl, trichloroethyl) are discussed.The pKa of trichloroethyl phenylcarbazate is 14.12 at 25 deg C.The pH profiles, the activation entropy of -40 cal mol-1 K-1, the kinetic solvent isotope effect, kOH-/kOD-, of 3.45, the general-base catalysis and the effect of the leaving group and of the substituent on the aromatic ring are in agreement with the involvement of a BAc2 reaction scheme.
- Safraoui, Adil,Calmon, Michelle,Calmon, Jean-Pierre
-
p. 1349 - 1352
(2007/10/02)
-
- PRODUCTION OF 1,1,1-TRIHALOGENO-2-ALKANOLS AND SOME OF THEIR PROPERTIES
-
The reaction of acyclic and carbocyclic carbonyl compounds with haloforms was studied in liquid ammonia and dimethylformamide in the presence of basic catalysts (t-BuOK, KOH).As a result of the reaction 1,1,1-trihalogeno-2-alkanols were obtained.They were used for the synthesis of 1,1,1-trihalogeno-2-methoxyalkanes, 1,1-dibromoalkenes, 1,1-dichloro-2-methoxyalkenes, and alkyl mono- and dichloromethyl ketones.
- Bal'on, Ya. G.,Shul'man, M. D.,Vakulenko, L. I.
-
p. 1231 - 1237
(2007/10/02)
-
- 5-amino or substituted amino 1,2,3-triazoles
-
Novel 5-amino or substituted amino 1,2,3-triazoles are disclosed as having anticoccidial activity. The compounds are useful for controlling coccidiosis when administered in minor quantities to animals, in particular to poultry, usually in admixture with animal sustenance.
- -
-
-
- 2-(2-imidazolin-2-yl)-pyridines and quinolines, process and intermediates for the preparation thereof, and use of said compounds as herbicidal agents
-
There are provided novel 2-(2-imidazolin-2-yl)pyridine and quinoline compounds, a process and intermediate compounds for the preparation thereof, and a method for controlling a wide variety of annual and perennial plant species therewith.
- -
-
-
- Lewis Acid Catalysis of Ene Addition of Chloral and Bromal to Olefins; Product Studies
-
The addition of chloral and bromal to a variety of alkyl-substituted alkenes has been investigated.The effect of the reaction of varying the Lewis acid catalyst and the structure of substrate have been studied.Anhydrous AlCl3 was found to be most effective catalyst, and ene-type adducts were the major products in most cases.Side reactions were observed with the less reactive systems leading, variously, to the formation of trihalogenoketones, hydrohalogenated ene adducts, and cyclic ethers.Conditions for optimising the yield of ene adducts were established in some cases.The trihalogenoketone by-products can be conveniently removed by a Grignard-type reaction.
- Benner, Jill P.,Gill, G. Bryon,Parrott, Stephen J.,Wallace, Brian
-
p. 291 - 313
(2007/10/02)
-
- Kinetics and Mechanism of Hydrolysis of 4-Phenylallophanates
-
The kinetics of hydrolysis of aryl and alkyl 4-phenylallophanates to phenyl urea and phenol or alcohol are studied.Acid-base catalysis, deuterium solvent isotope effects, and entropy of activation provide good evidence for a changeover in mechanism from E1cB for aryl allophanates to BAc2 for alkyl esters.The parameters of Hammett and Yukawa-Tsuno relationships for aryl esters and the non-linear Bronsted correlation with the pKa values of the leaving groups are in good agreement with the proposed mechanism.
- Sabbagh, Mohamed Mowafak Al,Calmon, Michelle,Calmon, Jean-Pierre
-
p. 1233 - 1238
(2007/10/02)
-
- Process for increasing sugar yield in sugarcane
-
There is provided a novel method for increasing sucrose yield in sugarcane by treating sugarcane a few weeks prior to harvest with a sucrose yield enhancing amount of a 2-(2-imidazolin-2-yl)pyridine compound.
- -
-
-
- Selective Reductions. 30. Effect of Cation and Solvent on the Reactivity of Saline Borohydrides for Reduction of Carboxylic Esters. Improved Procedures for the Conversion of Esters to Alcohols by Metal Borohydrides
-
A comparative study of the relative reactivity of saline borohydrides (Li, Na, Ca) for the reduction of carboxylic esters has been made in selected solvents (ether, tetrahydrofuran, diglyme, 2-propanol, and ethanol) at 25 deg C.In ether solvents the reactivity follows the trend LiBH4 > Ca(BH4)2 > NaBH4.On the other hand, in alcohol solvents the order of reactivity is Ca(BH4)2 > LiBH4 > NaBH4.The reactivities of LiBH4 in ethyl ether and THF, of Ca(BH4)2 in THF and 2-propanol, and of NaBH4 in ethanol proved to be promising for the reduction of esters.However, alcoholsolvents are not useful for reductions at elevated temperatures because the decomposition of the reagents becomes competitive with the reduction.A convenient synthetic procedure has been developed for the rapid conversion of esters to alcohols by using LiBH4 in ethyl ether, LiBH4 in THF, and Ca(BH4)2 in THF and utilizing essentially stoichiometric amounts of the reagents.The procedure involves adding toluene to the reaction mixture and bringing the temperature to 100 deg C while allowing the solvent do distill off.Following completion of the reaction, toluene is readily removed under vacuum and the reaction product hydrolyzed.These reductions were generally complete in 0.5 - 2.0 h, and high yields of alcohols (73-96percent) were isolated.A number of ester derivatives, including compounds containing nitro, halo, cyano, and alkoxy groups, diesters, and lactones were reduced by this procedure.The study demonstrated the high selectivity of these reagents, permitting the rapid reduction of the ester group in the presence of many substituents.However, unsaturated esters undergo simultaneous hydroboration when reduced by this procedure.
- Brown, Herbert C.,Narasimhan, S.,Choi, Yong Moon
-
p. 4702 - 4708
(2007/10/02)
-
- NUCLEOPHILIC SUBSTITUTION OF ALCOHOL AT PHOSPHORUS OF SPIRO ACYLOXYPHOSPHORANE : TRANSPHOSPHORANYLATION
-
Spiro acyloxyphosphoranes (S-AOPs, 1 and 3) underwent the nucleophilic substitution of alcohols at the phosphorus atom to give another S-AOPs (2) (Transphosphoranylation).Reaction mechanism and characteristics of the transphosphoranylation are described.
- Kobayashi, Shiro,Narukawa, Yukitoshi,Hashimoto, Takatsugu,Saegusa, Takeo
-
p. 1599 - 1602
(2007/10/02)
-
- Reaction of Cyanates with N- and N'-Substituted Carboxylic Hydrazides
-
N-Substituted carboxylic hydrazides react with aryl cyanate, 2,2,2-trichloroethyl cyanate and 2,2,2-trifluoroethyl cyanate 2 to form the 1-acylisosemicarbazides 7.On treatment of the N'-substituted (aralkyl, alkyl) carboxylic hydrazides 8 with the cyanates listed, the 2-imino-1,3,4-oxadiazolines 10 are obtained by elimination of phenol or 2,2,2-trihalogenoethanol.Reaction between 8 and cyanogen bromide and alkylation of the 2-amino-1,3,4-oxadiazoles 5 also yield 10.Two derivatives of 10 yielded the dimers 17.
- Neitzel, Michael,Zinner, Gerwalt
-
p. 867 - 878
(2007/10/02)
-
