- Ground and excited state hydrogen atom transfer reactions and cyclization of 2-acetylbenzoic acid
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We present experimental and theoretical studies of the ring-chain tautomerism (H-atom transfer and cyclization) for 2-acetylbenzoic acid at both ground and electronically first excited states. 1H and 13C NMR studies in solution confirm the existence of equilibrium between the open and ring structures at the ground state, with the ring one being dominant (～90%). Temperature-dependent 1H NMR experiments allowed obtaining the thermodynamic and kinetic parameters at the coalescence temperature (380 K). Fluorescence measurements disclose the involvement of highly efficient nonradiative processes in agreement with the theoretical data. Electronic calculations for the ground state give additional information on the different conformers of the open tautomer. In agreement with the experiment the most stable structure is of the closed ring tautomer, and it is obtained after additional internal rotations of the -COOH and -CO(CH3) fragments. Intrinsic reaction coordinate calculations indicate that the ring formation/breaking and the H-atom transfer are taking place in a concerted but not synchronous manner. At S1 the most stable form is the open one, for which different conformers are also found. The influence of the solvent is also accounted for through a model that considers the solvent as a continuum at both the ground and excited electronic states. No major differences were observed when comparing both gas and condensed phase results, so calculations of the isolated molecule should give a picture of the reaction which is experimentally observed in solution.
- Santos,Vargas,Moreno,Manzano,Lluch,Douhal
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Read Online
- Regio- and Stereoselective Synthesis of (Z)-3-Ylidenephthalides via H3PMo12O40-Catalyzed Cyclization of 2-Acylbenzoic Acids with Benzylic Alcohols
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We report an exclusively tandem C—O and C—C bond forming beyond the esterification and cyclization reaction of 2-acylbenzoic acids with alcohols to regio- and stereoselective synthesis of the (Z)-3-ylidenephthalides. The reaction uses the nontoxic, inexpensive H3PMo12O40 as catalyst and produces water as the sole by-product, making the reaction environmentally benign and sustainable. Moreover, this reaction features an eco-friendly reaction condition, facile scalability, and easy derivatization of the products to drugs and bioactive compounds. The mechanism studies and density functional theory calculations reveal that the appropriate acid catalyst is the key to the selectivity of this transformation.
- Yang, Guoping,Li, Ke,Lin, Xiaoling,Li, Yijin,Cui, Chengxing,Li, Shixiong,Cheng, Yuanyuan,Liu, Yufeng
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supporting information
p. 3017 - 3022
(2021/09/13)
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- Synthesis of dibenzocycloketones by acyl radical cyclization from aromatic carboxylic acids using methylene blue as a photocatalyst
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An efficient intramolecular radical cyclization reaction via photoredox catalysis was developed for the synthesis of dibenzocycloketone derivatives using methylene blue as a photosensitizer. This strategy could be widely used to synthesize large heterocycles due to the unique reactivity of phosphoranyl radicals formed by a polar/SET crossover between an aromatic carboxylic acid and a phosphine radical cation. Attractive features of this process include generation of an acyl radical by an inexpensive and metal-free photocatalyst, which effectively undergoes a cyclization process.
- Jiang, Hongshuo,Mao, Guijie,Wu, Hongfeng,An, Qi,Zuo, Minghui,Guo, Weihao,Xu, Chunzhao,Sun, Zhizhong,Chu, Wenyi
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supporting information
p. 5368 - 5373
(2019/10/11)
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- A biocatalytic method for the chemoselective aerobic oxidation of aldehydes to carboxylic acids
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Herein, we present a study on the oxidation of aldehydes to carboxylic acids using three recombinant aldehyde dehydrogenases (ALDHs). The ALDHs were used in purified form with a nicotinamide oxidase (NOx), which recycles the catalytic NAD+ at the expense of dioxygen (air at atmospheric pressure). The reaction was studied also with lyophilised whole cell as well as resting cell biocatalysts for more convenient practical application. The optimised biocatalytic oxidation runs in phosphate buffer at pH 8.5 and at 40 °C. From a set of sixty-one aliphatic, aryl-Aliphatic, benzylic, hetero-Aromatic and bicyclic aldehydes, fifty were converted with elevated yield (up to >99%). The exceptions were a few ortho-substituted benzaldehydes, bicyclic heteroaromatic aldehydes and 2-phenylpropanal. In all cases, the expected carboxylic acid was shown to be the only product (>99% chemoselectivity). Other oxidisable functionalities within the same molecule (e.g. hydroxyl, alkene, and heteroaromatic nitrogen or sulphur atoms) remained untouched. The reaction was scaled for the oxidation of 5-(hydroxymethyl)furfural (2 g), a bio-based starting material, to afford 5-(hydroxymethyl)furoic acid in 61% isolated yield. The new biocatalytic method avoids the use of toxic or unsafe oxidants, strong acids or bases, or undesired solvents. It shows applicability across a wide range of substrates, and retains perfect chemoselectivity. Alternative oxidisable groups were not converted, and other classical side-reactions (e.g. halogenation of unsaturated functionalities, Dakin-Type oxidation) did not occur. In comparison to other established enzymatic methods such as the use of oxidases (where the concomitant oxidation of alcohols and aldehydes is common), ALDHs offer greatly improved selectivity.
- Knaus, Tanja,Tseliou, Vasilis,Humphreys, Luke D.,Scrutton, Nigel S.,Mutti, Francesco G.
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supporting information
p. 3931 - 3943
(2018/09/11)
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- Aerobic Photooxidative Synthesis of β-Alkoxy Monohydroperoxides Using an Organo Photoredox Catalyst Controlled by a Base
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Transition-metal-free synthesis of β-alkoxy monohydroperoxides via aerobic photooxidation using an acridinium photocatalyst was developed. This method enables the synthesis of some novel hydroperoxides. The peroxide source is molecular oxygen, which is cost-effective and atomically efficient. Magnesium oxide plays an important role as a base in the catalytic system.
- Asano, Yuya,Nagasawa, Yoshitomo,Yamaguchi, Eiji,Itoh, Akichika
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supporting information
p. 409 - 412
(2018/02/21)
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- Room Temperature Carbonylation of (Hetero) Aryl Pentafluorobenzenesulfonates and Triflates using Palladium-Cobalt Bimetallic Catalyst: Dual Role of Cobalt Carbonyl
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An efficient method for the carbonylation of (hetero) aryl pentafluorobenzenesulfonates and triflates under exceptionally mild conditions using palladium/dicobalt octacarbonyl [Pd/Co2(CO)8] has been developed. Besides acting as carbon monoxide (CO) source, Co2(CO)8enhances the reaction rate by accelerating the CO insertion through an in situ generated bimetallic palladium cobalt tetracarbonyl [Pd-Co(CO)4] complex. Under the optimized reaction condition, carbonylation of a wide range of activated and deactivated, as well as sterically hindered and heteroaromatic, substrates proceeded efficiently at room temperature. The high chemoselectivity and improved synthesis of biologically relevant Isoguvacine and Lazabemide intermediates highlights its scope as a valuable synthetic method. The generality of this protocol was further extended to other electrophiles (bromides, chlorides and tosylates). (Figure presented.).
- Joseph, Jayan T.,Sajith, Ayyiliath M.,Ningegowda, Revanna C.,Shashikanth, Sheena
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p. 419 - 425
(2017/02/10)
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- Method for preparing isobenzofuran-1(3H)-one compounds
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The invention provides a method for preparing isobenzofuran-1(3H)-one compounds. R1, R2 and p are defined in the specification.
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Paragraph 0067; 0068; 0069; 0070; 0071; 0072; 0073
(2016/10/10)
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- Synthesis of (R)-3-methylphthalide by reductive cyclization of a 2-acylarylcarboxylate using the chiral boronic ester TarB-H and sodium borohydride
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Background: Phthalides are pervasive benzolactone structural frameworks in nature and have a broad profile of biological activities. Catalytic asymmetric reduction with the in situ lactonization of 2-acylarylcarboxylate compounds is an efficient strategy for chiral phthalide synthesis. The tartaric acid-derived reagent TarB-X is capable of mediating the asymmetric reduction of aromatic ketones using either LiBH4 or NaBH4 as the reductant. Up until now, the asymmetric reduction by Tarb- H/NaBH4 had not been applied to the synthesis of chiral phthalides. Methods: The requsite substrate, methyl 2-acetylbenzoate was obtained by a two step reaction starting from phthalic anhydride and maloninc acid. Tarb-H was obtained by treatment of L-(+)-tartaric acid with phenylboronic acid. The catalyst and NaBH4 were reacted with methyl 2-acetylbenzoate at room temperature for 1 h. The structure of (R)-3-Methylphthalide was established by NMR and mass spectrometry and its enantiomeric excess was determined by HPLC. The relative configuration was deduced by comparison of the optical rotation with data given in the literature. Results: (R)-3-Methylphthalide was obtained in moderte yield and high enantiomeric excess. Conclusion: (R)-3-methylphthalide was prepared in high enantiomeric excesses using an inexpensive and easily synthesized tartaric acid derived boronic ester (TarB-H) with sodium borohydride. The chiral phthalide was obtained in an open flask by reductive cyclization of a 2-acylarylcarboxylate.
- De Souza, Aline Aparecida Nunes,Taylor, Jason Guy
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p. 657 - 660
(2017/01/16)
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- MIL-101 as reusable solid catalyst for autoxidation of benzylic hydrocarbons in the absence of additional oxidizing reagents
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Materiaux de l'Institute Lavosier-101 (MIL-101) promotes benzylic oxidation of hydrocarbons exclusively by molecular oxygen in the absence of any other oxidizing reagent or initiator. Using indane as model compound, the selectivity toward the wanted ol/one mixture is higher for MIL-101(Cr) (87% selectivity at 30% conversion) than for MIL-101(Fe) (71% selectivity at 30% conversion), a fact that was associated with the preferential adsorption of indane within the pore system. Product distribution and quenching experiments with 2,2,6,6-tetramethyl-1-piperidinyloxy, benzoic acid, and dimethylformamide show that the reaction mechanism is a radical chain autoxidation of the benzylic positions by molecular oxygen, and the differences in selectivity have been attributed to the occurrence of the autoxidation process inside or outside the metal organic framework pores. MIL-101 is reusable, does not leach metals to the solution, and maintains the crystal structure during the reaction. The scope of the benzylic oxidation was expanded to other benzylic compounds including ethylbenzene, n-butylbenzene, iso-butylbenzene, 1-bromo-4-butylbenzene, sec-butylbenzene, and cumene.
- Santiago-Portillo, Andrea,Navalón, Sergio,Cirujano, Francisco G.,Xamena, Francesc X. Llabrés I,Alvaro, Mercedes,Garcia, Hermenegildo
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p. 3216 - 3224
(2015/06/16)
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- Electrophilicity and nucleophilicity of commonly used aldehydes
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The present approach for determining the electrophilicity (E) and nucleophilicity (N) of aldehydes includes a kinetic study of KMNO4 oxidation and NaBH4 reduction of aldehydes. A transition state analysis of the KMNO4 promoted aldehyde oxidation reaction has been performed, which shows a very good correlation with experimental results. The validity of the experimental method has been tested using the experimental activation parameters of the two reactions. The utility of the present approach is further demonstrated by the theoretical versus experimental relationship, which provides easy access to E and N values for various aldehydes and offers an at-a-glance assessment of the chemical reactivity of aldehydes in various reactions. the Partner Organisations 2014.
- Pratihar, Sanjay
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p. 5781 - 5788
(2014/07/22)
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- NOVEL PROCESS
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Disclosed herein is novel process for preparation of atovaquone, which process includes reacting1H-2-benzopyran-1,4(3H)-dione with 4-(4-chlorophenyl)cyclohexanecarbaldehyde. The invention further discloses novel intermediates useful in the preparation of atovaquone.
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Page/Page column 15
(2012/06/30)
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- Discovery and development of an efficient process to atovaquone
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The discovery and development of an efficient and more sustainable manufacturing route to the antipneumocystic agent atovaquone (2-((1R,4R)-4-(4-chlorophenyl)cyclohexyl)-3-hydroxynaphthalene-1,4-dione) 1 is described. The existing commercial route to atovaquone delivers a poor yield of product and uses expensive reagents. The new synthesis commences with readily available phthalic anhydride, which is converted to 1,4-isochromandione 5 and then to atovaquone 1 by reaction with 4-(4-chlorophenyl)cyclohexanecarboxylic acid 3 using key bromination, Rosenmund reduction, and rearrangement chemistries. Downstream processing to atovaquone is both high yielding and robust, and the resulting process has been demonstrated on 200-kg scale. The process is simple, uses cheap raw materials, and is more sustainable in that it avoids lowyielding silver-promoted chemistry and isomerisation procedures. It includes a robust, facile, and highly efficient procedure to 1,4-isochromandione 5, and routes to 4-(4-chlorophenyl)cyclohexanecarboxaldehyde 9 have also been developed, including a Rosenmund method that was demonstrated on pilot-plant scale. Also discussed are the route-derived impurities and processing amendments to control their formation.
- Britton, Hugh,Catterick, David,Dwyer, Andrew N.,Gordon, Andrew H.,Leach, Stuart G.,McCormick, Chris,Mountain, Clive E.,Simpson, Alec,Stevens, David R.,Urquhart, Michael W. J.,Wade, Charles E.,Warren, John,Wooster, Nick F.,Zilliox, Audrey
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p. 1607 - 1617
(2013/02/23)
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- Kinetics of proton transfer between ortho substituted benzoic acids and the carbinol base of crystal violet in toluene. Ortho effect on the reactivity of benzoic acids in apolar aprotic solvents
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Apolar aprotic solvents are particularly advantageous for investigating the intrinsic ortho effect free from complications of specific solvent effects. A kinetic study for toluene-phase proton transfers between ortho F, Cl, Br, I, OMe, OEt, OPh, OAc, Me, NO2, COMe, COPh, OH, NH2, and H benzoic acids and crystal violet carbinol base has shown the forward rate constant (log k+1) is the most appropriate reactivity parameter in toluene. log k+1 (toluene) as compared to other reported reactivity parameters in benzene, toluene, or chlorobenzene has been found more sensitive to the ortho substituent effect. The regression results of the correlation of log k+1 (toluene) of the acids (except OH and NH2 substituted ones) according to seven ortho effect models are all very significant, and the best result is given by Fujita-Nishiokas model. The overall analysis reveals that a substituents ortho effect pattern is a 58:24:18 ratio of its ordinary electrical, proximity electrical, and steric effects and that the proximity electrical effect is the major component to account for the peculiarity of the substituents ortho effect. The results further favor the transmission of this effect mainly through the molecular cavity. The effect may, however, be outweighed by the steric component for bulky enough substituents, e.g., Me. The enhanced strength exhibited by salicylic acid in toluene has been quantitatively described using Pytela-Lisas δHB i parameter. The abnormally high log k+1 observed for anthranilic acid in toluene has been ascribed to a very extensive homoconjugation in its acid-acid anion complex induced by the acids three hydrogen bond donors.
- Sen Gupta, Susanta K.,Mishra, Sangeeta
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experimental part
p. 4616 - 4623
(2011/06/26)
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- Selective oxidation of acetophenones bearing various functional groups to benzoic acid derivatives with molecular oxygen
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Acetophenones substituted by alkyl, alkoxy, acetoxy, and halogen groups were selectively oxidized with molecular oxygen to the corresponding benzoic acids by using the N,N',N"-trihydroxyisocyanuric acid (THICA)/cobalt(II) acetate [Co(OAc)2] and THICA/Co(OAc)2/manganese(II) acetate.
- Nakamura, Ryota,Obora, Yasushi,Ishii, Yasutaka
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experimental part
p. 1677 - 1684
(2011/02/25)
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- Catalytic enantioselective synthesis of chiral phthalides by efficient reductive cyclization of 2-acylarylcarboxylates under aqueous transfer hydrogenation conditions
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A new diamine ligand for asymmetric transfer hydrogenation (ATH) was discovered. The reductive cyclization of 2-acylarylcarboxylates was found to proceed highly stereoselective by the new Ru complex-catalyzed ATH and subsequent In situ lactonization under aqueous conditions. It enables efficient access to a wide variety of 3-substituted phthalides In enantiomerically pure form.
- Zhang, Bo,Xu, Ming-Hua,Lin, Guo-Qiang
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supporting information; experimental part
p. 4712 - 4715
(2009/12/08)
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- Palladium-catalyzed hydroxycarbonylation of aryl and vinyl triflates by in situ generated carbon monoxide under microwave irradiation
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An operationally simple hydroxycarbonylation of aryl and vinyl inflates to the corresponding carboxylic acids with a palladium-mediated microwave system was carried out in water. Georg Thieme Verlag Stuttgart.
- Lesma, Giordano,Sacchetti, Alessandro,Silvani, Alessandra
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p. 594 - 596
(2007/10/03)
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- Synthesis and anticancer activities of novel 1,4-disubstituted phthalazines
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A series of novel 1-anilino-4-(arylsulfanylmethyl)phthalazines were designed and synthesized. The structures of all the compounds were confirmed by IR, 1H-NMR, elemental analysis and MS. The analogues 1-(3-chloro-4-fluoroanilino)-4-(3,4-difluorophenylthio-methyl)phthalazine (12) and 1-(4-fluoro-3-trifluoromethylanilino)-4-(3,4-difluorophenyl-thiomethyl) phthalazine (13) showed higher activity than a cisplatin control when tested in vitro against two different cancer cell lines using the microculture tetrazolium method (MTT) method.
- Li, Juan,Zhao, Yan-Fang,Yuan, Xiao-Ye,Xu, Jing-Xiong,Gong, Ping
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p. 574 - 582
(2007/10/03)
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- Method for preparing chiral diphosphines
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The invention concerns a method for preparing a compound of formula (1) wherein: A represents naphthyl or phenyl optionally substituted; and Ar1, Ar2independently represent a saturated or aromatic carbocyclic group, optionally substituted.
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- Palladium-catalyzed synthesis of o-acetylbenzoic acids: A new, efficient general route to 2-hydroxy-3-phenyl-1,4-naphthoquinones and indolo[2,3-b]naphthalene-6,11-diones
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We describe here a new, efficient general synthesis of o-acetylbenzoic acids by Heck palladium-catalyzed arylation of n-butyl vinyl ether with o-bromobenzoic acid esters and the use of these compounds as starting materials for the synthesis of 3-benzylideneisochroman-1,4-diones, which readily rearrange to 2-hydroxy-3-phenyl-1,4-naphthoquinones. The application of this strategy to the synthesis of indolo[2,3-b]naphthalene-6,11-diones is also described.
- Barcia, José C,Cruces, Jacobo,Estévez, Juan C,Estévez, Ramón J,Castedo, Luis
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p. 5141 - 5144
(2007/10/03)
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- Controlled release of perfumery alcohols by alkaline hydrolysis of 2-formyl- and 2-acetylbenzoates and their corresponding phthalides
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The controlled release of perfumery alcohols by alkaline hydrolysis of 2-formyl- and 2-acetylbenzoates and their corresponding phthalides were investigated. The rate of benzoate hydrolysis depended on the structure of alcohol released. It was suggested th
- Enggist, Paul,Rochat, Sabine,Herrmann, Andreas
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p. 438 - 440
(2007/10/03)
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- C-C-bond formation in reactions of [(η5-C5H4SiMe3)2Ti(C?CR1)2]CuR with acyl chlorides and anhydrides
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The chemical behaviour of selected {[Ti](C?CR1)2}CuR complexes (1a: R1=SiMe3, R=CH3; 1b: R1=tBu, R=CH3; 1c: R1=tBu, R=C?CSiMe3) towards a number of different acyl chlorides and anhydrides is described. The reaction of 1a or 1b with R2C(O)Cl (2a: R2=CH3, 2b: R2=C6H5) produces the ketones R2C(O)R (4a: R=R2=CH3; 4b: R=CH3, R2=C6H5; 4c: R=C?CSiMe3, R2=CH3, 4d: R=C?CSiMe3, R2=C6H5) along with {[Ti](Cnequiv;CR1)2}CuCl (3a: R1=SiMe3, 3b: R1=tBu). However, on treatment of 1b or 1c with [CH3C(O)]2O (5a) the ketones 4a or 4c are formed along with the copper(I) acetate complex {[Ti](C?CtBu)2}CuOC(O)CH3 (6), while the reaction of 1b or 1c with CH3CO2H (5b) yields methane and 6. In addition, when 1b or 1c are reacted with maleic (7), phthalic (9a) or tetrachlorophthalic anhydride (9b) the copper(I) carboxylates {[Ti](C?CtBu)2}CuOC(O)-cis-CH=CH-C(O)R (8a: R=CH3, 8b: R=C?CSiMe3) and {[Ti](C?CtBu)2}CuOC(O)-C6H4-n Cln-2-C(O)R (10a: n=0, R=CH3; 10b: n=0, R=C?CSiMe3; 10c: n=4, R=C?CSiMe3) are produced, which upon addition of, e.g. HBr afford via cleavage of the copper-oxygen σ-bond {[Ti](C?CtBu)2}CuBr (3c) and the corresponding carboxylic acids cis-HO2C-CH=CH-C(O)CH3 (11a) or HO2C-C6H4-2-C(O)CH3 (11b), respectively.
- Frosch,Back,Lang
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p. 140 - 147
(2007/10/03)
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- Asymmetric hydrogenation method of a ketonic compound and derivative
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The present invention relates to a process for the asymmetric hydrogenation of a ketonic compound and derivative. The invention relates to the use of optically active metal complexes as catalysts for the asymmetric hydrogenation of a ketonic compound and derivative. The process for the asymmetric hydrogenation of a ketonic compound and derivative is characterized in that the asymmetric hydrogenation of said compound is carried out in the presence of an effective amount of a metal complex comprising as ligand an optically active diphosphine corresponding to one of the following formulae: STR1
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- Ring-chain tautomerism. Part 10 +. The reaction of oxocarboxylic acids with diazodiphenylmethane
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The rate coefficients for the esterification of a series of oxocarboxylic acids with diazodiphenylmethane have been determined in ethanol or 2-methoxyethanol at 30.0°C. These and the rates of reaction with model compounds have been used to estimate the equilibrium constants for ring-chain tautomerism for the oxocarboxylic acids.
- Bowden, Keith,Misic-Vukovic, Milica M.,Ranson, Richard J.
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p. 1601 - 1606
(2007/10/03)
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- Prodrugs - Part 2. Acylbenzoate esters of metronidazole
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The design and synthesis of a series of chain and cyclic acylbenzoate esters of metronidazole are described. The esters are designed to be both lipophilic and reactive in their hydrolysis reactions. The alkaline hydrolyses of the chain 2-acylbenzoates are relatively rapid, employing an intramolecular catalytic route, while the reactions of the 4-formylbenzoate and cyclic 2-formylbenzoate are also relatively rapid using the normal pathway. The anti-bacterial activity of the esters are comparable to that of metronidazole.
- Bowden,Izadi
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p. 995 - 1000
(2007/10/03)
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- Microbial asymmetric syntheses of 3-alkylphthalide derivatives
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Phthalide derivatives, almost all of which have an S-configuration, have a wide range of activity and exist in Angerica sinensis Diels and Sligusticum wallichiii Franch. For the first time, optically active (S)-3-methylphthalide derivatives were synthesized using two methods, asymmetric microbial reduction and microbial hydroxylation. For the first method, methyl 2-acetylbenzoate was synthesized as a substrate, which was reduced asymmetrically by Geotrichum candidum IFO 34614 to obtain (S)-3-methylphtalide in 92% yield (99% enantiomeric excess, ee). For the second method, 2-ethylbenzoic acid was employed as a substrate which was hydroxylated asymmetrically at the benzylic position by either Pseudomonas putida ATCC 12633 or Aspergillus niger IFO 6661, whose fermentation was induced by o-toluic acid, to obtain (S)-3-methylphthalide in 80% yield (99% ee). (S)-3-Butylphthalide and (S)-3-octylphthalide were obtained in the same manner in 12% yield (ee = 99%) and 10% yield (ee = 99%), respectively.
- Kitayama, Takashi
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p. 3765 - 3774
(2007/10/03)
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- PHOTOLYSIS OF SUBSTITUTED NAPHTHALENES ON SiO2 AND Al2O3
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Photolysis of naphthalene on the surface of SiO2 under an atmosphere of air produces phthalic acid as the only major photoproduct, accounting for 49percent of the consumed naphthalene.Photolysis on Al2O3 also produces phthalic acid, in 31percent yield.Photolysis of 1-methylnaphthalene on SiO2 proceeds under similar conditions to produce 2-acetylbenzoic acid (35percent) as the major photoproduct with the production of a small amount of 1-naphthaldehyde (6percent). 1-Cyanonaphthalene does not photooxidize under similar conditions.The presence of oxygen is necessary for the photodecompositionof naphthalene and 1-methylnaphthalene to proceed.Superoxide formed from the photolysis of naphthalene at the SiO2/air interface is readily observed by electron paramagnetic resonance spectroscopy.In the absence of naphthalene no superoxide is observed.A mechanism involving electron transfer from the S1 state of the naphthalene to O2 is proposed on the basis of these observations and related literature precedent.
- Barbas, John T.,Sigman, Michael E.,Buchanan, A.C.,Chevis, Eddie A.
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p. 155 - 158
(2007/10/02)
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- Autoxidation of alkylnaphthalenes. 2. Inhibition of the autoxidation of n-hexadecane at 160 °C
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The rate of the self-initiated autoxidation of hexadecane at 160 °C under 760 Torr of O2 is reduced by the addition of submolar concentrations of naphthalene or alkylnaphthalene. The kinetics of these (alkyl)naphthalene-modulated, self-initiated hexadecane autoxidations have been examined by monitoring hydroperoxide concentrations. Under similar conditions, the extent of the rate retardation is essentially identical for equal concentrations of naphthalene and 1- and 2-methylnaphthalene (and 2-sec-butylnaphthalene), which proves that retardation is due to chemistry associated with the naphthalene moiety. It is shown that the (alkyl)naphthalene produces both an increase in the rate constant for a bimolecular, peroxyl + peroxyl chain-termination process and a kinetically-first-order chain-termination reaction. Both of these termination processes are attributed to an initial addition of hexadecylperoxyl radicals to the naphthalene ring. Reaction of the resultant peroxycydohexadienyl radical with O2 produces the HOO? radical which is responsible for the increase in the rate constant for bimolecular termination. Unimolecular decomposition of the peroxycyclohexadienyl radical yields hexadecanol and an (alkyl)naphthoxyl radical, the latter being responsible for the kinetically-first-order termination process. A simplified scheme of 17 elementary reactions yields a kinetic expression which, via computer modeling, is shown to give a very satisfactory agreement between calculated and measured hydroperoxide yields under all experimental conditions surveyed. This simulation yields a rate constant k19 of ～70 M-1 s-1 for the addition of hexadecylperoxyl radicals to (alkyl)naphthalenes at 160 °C, a value which may be compared with the estimated rate constant for hydrogen abstraction from 1- or 2-methylnaphthalene under similar conditions, viz., k15 = 34 M-1 s-1. The simulation also gives a satisfactory agreement between calculated and measured yields of organic hydroperoxides and hydrogen peroxide. That the naphthalene ring was oxidatively cleaved under the experimental conditions was demonstrated by the identification of phthalic acid and phthalic anhydride following the addition of naphthalene or a methylnaphthalene to autoxidizing hexadecane. Both 1- and 2-methylnaphthalene also yielded 2-acetylbenzoic acid. The possible mechanisms by which these naphthalene ring-cleaved products are formed are discussed.
- Igarashi,Jensen,Lusztyk,Korcek,Ingold
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p. 7727 - 7736
(2007/10/02)
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- Reactions of 3-Acetyltropolone Methyl Ethers with Guanidine and Amidines
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3-Acetyl-2-methoxytropone (1a) rearranged to 2-acetylbenzoic acid (2) on treatment with guanidine in the presence of sodium ethoxide, and reacted with benzamidine to give 4-methyl-2-phenyl-9H-cycloheptapyrimidin-9-one (5).Reaction with guanidine carbonate in the absence of sodium ethoxide gave 2-amino-4-methyl-9H-cycloheptapyrimidin-9-one (4). 2-Acetyl-7-methoxytropone (1b) reacted with guanidine, benzamidine, and acetamidine to afford 4-acetyl-2-aminocycloheptimidazole (3), 4-acetyl-2-phenylcycloheptimidazole (6), and 2-acetyl-7-aminotropone (7), respectively.
- Jin, Zhong-Tian,Imafuku, Kimiaki,Matsumura, Hisashi
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p. 1037 - 1040
(2007/10/02)
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- N-Cyclopropylisoindolines
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Compounds of the general formula: STR1 in which A is a benzene ring or a carbocyclic aromatic group consisting of two or three fused benzene rings, the group A being linked to the nitrogen containing ring at two adjacent carbon atoms and the benzene ring or each benzene ring optionally carrying one or more substituents which may be the same or different, and may be alkyl, aryl, halo, hydroxy, acyloxy or alkoxy, or two adjacent positions in a ring may be substituted so as to form a methylene dioxy group (--O--CH2 --O--); R1 and R2 which may be the same or different, each represent hydrogen; an alkyl group which contains 1 to 6 carbon atoms and which may be substituted; a hydroxycarbonyl or an alkoxycarbonyl group; and one of R3 and R4 represents hydrogen, an alkyl group which contains 1 to 6 carbon atoms and which may be substituted, or a hydroxy, alkoxy, hydroxycarbonyl or alkoxycarbonyl group and the other of R3 and R4 represents hydrogen, or a non-toxic physiologically acceptable salt or bioprecursor thereof. These compounds are useful in the treatment of patients suffering from depression.
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- Reactions of 2-Acyl-1,3-indandiones
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2-Pivaloyl-1,3-indandione reacts with thiosemicarbazide in aqueous base, through two successive retro-Claisen reactions, to yield 1-hydroxy-4-methylphthalazine.The mechanism of this reaction is described.Under similar conditions, 2-benzoyl and 2-acetyl-1,3-indandione, did not undergo the same reaction, a steric factor is considered.
- Lemke, Thomas L.,Parker, George R.
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p. 1519 - 1520
(2007/10/02)
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