- REARRANGEMENT OF DIMETHYLPHENYLACYLATES USING ZEOLITES
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The present invention relates to a Fries rearrangement of specific dimethylphenylacylates to form the desired respective hydroxyaryl ketones having two methyl groups bound to the aromatic ring. It has been found that the process is surprisingly very specific in view of the number and position of the methyl group(s) bound to the aromatic ring.
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Page/Page column 9-10; 14
(2021/08/14)
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- Substrate substitution effects in the Fries rearrangement of aryl esters over zeolite catalysts
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The catalytic transformation of aryl esters to hydroxyacetophenones via Fries rearrangement over solid acids is of interest to avoid the use of corrosive and toxic Lewis and Br?nsted acids traditionally applied. Microporous zeolites are known to catalyze the reaction of simple substrates such as phenyl acetate, but their application to substituted derivatives has received limited attention. To refine structure-activity relationships, here we examine the impact of various parameters including the solvent polarity, water content, acidic properties, and framework type on the reaction scheme in the Fries rearrangement of p-tolyl acetate over common solid acids. The results confirm the importance of providing a high concentration of accessible Br?nsted acid sites, with beta zeolites exhibiting the best performance. Extension of the substrate scope by substituting methyl groups in multiple positions identifies a framework-dependent effect on the rearrangement chemistry and highlights the potential for the transformation of dimethylphenyl acetates. Kinetic studies show that the major competitive path of cleavage of the ester C-O bond usually occurs in parallel to the Fries rearrangement. The possibility of sequentially acylating the resulting phenol depends on the substrate and reaction conditions.
- Bonrath, Werner,Létinois, Ulla,Lin, Ronghe,Medlock, Jonathan,Mitchell, Sharon,Netscher, Thomas,Pérez-Ramírez, Javier,Stemmler, René T.
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p. 4282 - 4292
(2020/07/30)
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- An Enzymatic Route to α-Tocopherol Synthons: Aromatic Hydroxylation of Pseudocumene and Mesitylene with P450 BM3
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Aromatic hydroxylation of pseudocumene (1 a) and mesitylene (1 b) with P450 BM3 yields key phenolic building blocks for α-tocopherol synthesis. The P450 BM3 wild-type (WT) catalyzed selective aromatic hydroxylation of 1 b (94 %), whereas 1 a was hydroxylated to a large extent on benzylic positions (46–64 %). Site-saturation mutagenesis generated a new P450 BM3 mutant, herein named “variant M3” (R47S, Y51W, A330F, I401M), with significantly increased coupling efficiency (3- to 8-fold) and activity (75- to 230-fold) for the conversion of 1 a and 1 b. Additional π–π interactions introduced by mutation A330F improved not only productivity and coupling efficiency, but also selectivity toward aromatic hydroxylation of 1 a (61 to 75 %). Under continuous nicotinamide adenine dinucleotide phosphate recycling, the novel P450 BM3 variant M3 was able to produce the key tocopherol precursor trimethylhydroquinone (3 a; 35 % selectivity; 0.18 mg mL?1) directly from 1 a. In the case of 1 b, overoxidation leads to dearomatization and the formation of a valuable p-quinol synthon that can directly serve as an educt for the synthesis of 3 a. Detailed product pattern analysis, substrate docking, and mechanistic considerations support the hypothesis that 1 a binds in an inverted orientation in the active site of P450 BM3 WT, relative to P450 BM3 variant M3, to allow this change in chemoselectivity. This study provides an enzymatic route to key phenolic synthons for α-tocopherols and the first catalytic and mechanistic insights into direct aromatic hydroxylation and dearomatization of trimethylbenzenes with O2.
- Dennig, Alexander,Weingartner, Alexandra Maria,Kardashliev, Tsvetan,Müller, Christina Andrea,Tassano, Erika,Schürmann, Martin,Ruff, Anna Jo?lle,Schwaneberg, Ulrich
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p. 17981 - 17991
(2017/11/29)
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- Construction of Acid–Base Synergetic Sites on Mg-bearing BEA Zeolites Triggers the Unexpected Low-Temperature Alkylation of Phenol
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Novel Mg-bearing BEA zeolites are synthesized to simultaneously endow significantly enhanced basicity without compromising acidity over the zeolite framework. Serving as efficient solid acid–base bifunctional catalysts, they achieve the liquid-phase selective methylation of phenol with methanol to produce o- and p-cresol (o/p=2) under mild conditions. The method is readily extendable to the alkylation of phenols with various alcohols. Stereo- and regioselectivity (>95 % for p-product) was attained on the alkylation of phenol with bulky tert-butyl alcohol, rendering the first acid–base cooperative shape-selective catalysis relying on the basicity of zeolites. A preliminary mechanistic analysis reveals that the remarkable activity and shape-selectivity come from the superior special acidic–basic synergetic catalytic sites on the uniform microporous channels of the BEA zeolite.
- Xie, Jingyan,Zhuang, Wenxia,Zhang, Wei,Yan, Ning,Zhou, Yu,Wang, Jun
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p. 1076 - 1083
(2017/03/27)
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- Selective oxidation of pseudocumene and 2-methylnaphthalene with aqueous hydrogen peroxide catalyzed by γ-Keggin divanadium-substituted polyoxotungstate
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The catalytic performance of a γ-Keggin divanadium-substituted phosphotungstate, (Bu4N)4[γ-PW10O38V2(μ-O)(μ-OH)], has been evaluated in the selective oxidation of 1,2,4-trimethylbenzene (pseudocumene, PC) and 2-methylnaphthalene with the green oxidant, 35% aqueous hydrogen peroxide. Under conditions of H2O2 deficiency ([PC]/[H2O2] = 17-22), PC oxidation proceeded with unusually high chemo- and regioselectivity, producing exclusively 2,4,5-trimethylphenol (2,4,5-TMP) and 2,3,5-TMP in a molar ratio of 7.3/1 and a yield of 73% based on the oxidant. Isomeric 2,3,6-trimethylphenol was found in trace amounts. Under conditions of H2O2 excess ([H2O2]/[PC] = 8), 2,3,5-trimethyl-1,4-benzoquinone (TMBQ, vitamin E key intermediate) formed with 41% selectivity at 41% substrate conversion. Atypical regioselectivity was also found in the oxidation of 2-methylnaphthalene which gave predominantly 6-methyl-1,4-naphthoquinone (6-MNQ) rather than isomeric 2-MNQ. The ratio between the isomers could be altered by varying the catalyst and oxidant amounts.
- Zalomaeva, Olga V.,Evtushok, Vasiliy Yu.,Maksimov, Gennadii M.,Kholdeeva, Oxana A.
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p. 210 - 216
(2015/09/01)
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- Selective oxidative homo-and cross-coupling of phenols with aerobic catalysts
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Simple catalysts that use atom-economical oxygen as the terminal oxidant to accomplish selective ortho-ortho, ortho-para, or para-para homo-couplings of phenols are described. In addition, chromium salen catalysts have been discovered as uniquely effective in the cross-coupling of different phenols with high chemo-and regioselectivity.
- Lee, Young Eun,Cao, Trung,Torruellas, Carilyn,Kozlowski, Marisa C.
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supporting information
p. 6782 - 6785
(2014/06/09)
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- A total synthesis of yellowish aphid pigment furanaphin through fries rearrangement assisted by boron trifluoride-acetic acid complex
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The yellowish aphid pigment furanaphin, isolated from Aphis spiraecola and possessing cytotoxicity against HL-60 (human promyelocytic leukemia-60) cells, was synthesized by utilizing the Fries rearrangement assisted with a BFmiddot;2AcOH complex as a key step. It was confirmed that the complex effectively mediated the reaction even though the compounds had an electron-withdrawing substituent.
- Nishimura, Taichi,Iwata, Takeki,Maegawa, Hironori,Nishii, Takeshi,Matsugasako, Masami,Kaku, Hiroto,Horikawa, Mitsuyo,Inai, Makoto,Tsunoda, Tetsuto
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scheme or table
p. 1789 - 1792
(2012/08/29)
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- The use of Hagemann's Esters to prepare highly functionalized phenols and benzenes
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Hagemann's esters can be converted into highly functionalized phenols or arenes. The systematic functionalization of Hagemann's ester derivatives permits the preparation of tri-and tetraalkyl-substituted phenols or tetra-, penta-, and hexaalkyl-substituted benzenes. Kotnis's aromatization procedure was found to be solvent dependent, and Suzuki couplings were found to be sensitive to steric hindrance. Wittig olefination and ortho-Claisen reactions were reliable means to introduce alkyl substituents at C-4 and/or C-5 positions, respectively. The acid-promoted dehydration of tertiary alcohol 46 to produce enone 47, followed by its selective alkylation (cf. 48) is new. ARKAT USA, Inc.
- Majetich, George,Allen, Scott
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p. 104 - 124
(2012/11/07)
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- Catalytic activity of a mordenite catalyst in alkylation of xylenols with methanol
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The catalytic activity of a palladium-containing mordenite catalyst in alkylation of 2,6-, 2,4-, 2,5-, 2,3-, 3,4-, and 3,5-xylenols with methanol was studied. The main and by-products of catalysis and the activity of the catalyst in synthesis of individual trimethylphenols were determined.
- Agaev,Madatzade
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p. 683 - 684
(2007/10/03)
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- Metal ion promoted transesterifications of carboxylate esters. A structure/activity study of the efficacy of Zn2+ and La3+ to catalyze the methanolysis of some aryl and aliphatic esters
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The methanolysis of various aryl and aliphatic carboxylate esters promoted by methoxide, 1,5,9-triazacyclododecane: Zn2+(-OCH 3) and La3+(-OCH3), were studied and the derived rate constants (kOCH3, kcat 3:Zn(OCH3) and kcatLa(OCH3)) correlated in various ways. The metal ion catalyzed reactions are very much faster than the background reactions in some cases reaching up to 7 × 106-fold acceleration when present at concentrations of 5 mmol dm-3. The data for both metals exhibit non-linear Bronsted correlations with the pK a of the leaving group which are analyzed in terms of a change in rate limiting step from formation to breakdown of a metal-coordinated tetrahedral intermediate as the pKa increases above values of ~14.7. Plots of the log kOCH3 reaction vs. the log k cat, values for each metal ion indicate low sensitivity for aryl esters and a higher sensitivity for the aliphatic esters. A mechanistic rationale for the observations is presented.
- Neverov, Alexei A.,Sunderland,Brown, R. Stan
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- Ortho-alkylation of phenol with methanol using Pb-Cr promoted magnesium oxide catalysts
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In this study, Pb-Cr promoted magnesium oxide catalysts were used to catalyze the ortho-alkylation of phenol in the presence of excess methanol. The Cr/MgO catalyst exhibited a high conversion of phenol and a relatively high selectivity for the ortho-alkylation of phenol. The catalytic activity and the stability of Cr/MgO were improved by the addition of a fairly small amount of Pb. The Pb-Cr/MgO catalyst showed specificity for the ortho-alkylation of phenol, which was proved by a series of phenol derivative reactions with methanol.
- Ke, Jyh-Harng,Zena, Jyh-Myng,Wang, Fey-Long
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p. 1407 - 1410
(2007/10/03)
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- A convenient ring formation of 3-aryl-2,2-dialkyl-2,3-dihydrobenzofurans from phenols and 2-aryl-2,2-dialkylacetaldehydes
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A new and simple route for the preparation of 3-aryl-2,2-dialkyl-2,3- dihydrobenzofurans from phenols is described. In the presence of an acid catalyst phenols react with 2-aryl-2,2-dialkylacetaldehydes, prepared in good yield from 2-arylacetonitriles in 2 steps, to give 3-aryl-2,2-dialkyl-2,3- dihydrobenzofurans. Electron-donating substituents were required on the phenols in order to give 3-aryl-2,2-dialkyl-2,3-dihydrobenzofurans in good yield.
- Yamashita, Makoto,Ono, Yujirou,Tawada, Hiroyuki
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p. 2843 - 2849
(2007/10/03)
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- Process for functionalising a phenolic compound carrying an electron-donating group
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The invention concerns a method for functionalizing a phenolic compound bearing an electron-donor group, in said group para position, inter alia a method for the amidoalkylation of a phenolic compound bearing an electron-donor group, and more particularly, a phenolic compound bearing an electron-donor group preferably, in the hydroxyl group ortho position. The method for functionalizing in para position with respect to an electron-donor group carried by a phenolic compound is characterised in that the phenolic compound bearing an electron-donor group is subjected to the following steps: a first step which consists of protecting the hydroxyl group in the form of a sulphonic ester function; a second step which consists in reacting the protected phenolic compound with an electrophilic reagent; optionally, a third step deprotecting the hydroxyl group.
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- Low-valent titanium mediated reductive cleavage of O/N-trityl bonds via free radical pathway
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Low-valent titanium mediated cleavage of trityl-O/N bonds in trityl ethers/amines via electron transfer process is reported. Chemoselective deprotection of trityl ethers in preference to benzyl ethers is achieved. The ease of cleavage of protected alcohols and amines is in the order O-allyl > O-trityl > O-benzyl; N-trityl > O-trityl bonds.
- Rele, Shyam,Nayak, Sandip K.
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p. 3533 - 3540
(2007/10/03)
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- Indium metal as a reducing agent in organic synthesis
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The low first ionisation potential (5.8 eV) of indium coupled with its stability towards air and water, suggest that this metallic element should be a useful reducing agent for organic substrates. The use of indium metal for the reduction of C=N bonds in imines, the heterocyclic ring in benzo-fused nitrogen heterocycles, of oximes, nitro compounds and conjugated alkenes and the removal of 4-nitrobenzyl protecting groups is described. Thus the heterocyclic ring in quinolines, isoquinolines and quinoxalines is selectively reduced using indium metal in aqueous ethanolic ammonium chloride. Treatment of a range of aromatic nitro compounds under similar conditions results in selective reduction of the nitro groups; ester, nitrile, amide and halide substituents are unaffected. Likewise indium in aqueous ethanolic ammonium chloride is an effective method for the deprotection of 4-nitrobenzyl ethers and esters. Indium is also an effective reducing agent under non-aqueous conditions and α-oximino carbonyl compounds can be selectively reduced to the corresponding N-protected amine with indium powder, acetic acid in THF in the presence of acetic anhydride or di-tert-butyl dicarbonate. Conjugated alkenes are also reduced by indium in THF-acetic acid.
- Pitts,Harrison,Moody
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p. 955 - 977
(2007/10/03)
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- A facile route to the deprotection of sulfonate esters and sulfonamides with low valent titanium reagents
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A novel method for the cleavage of N/O-tosyl bonds by low-valent titanium is reported. TBDPS ether, THP ether, and olefin are found to be compatible under the reaction conditions.
- Nayak
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p. 1575 - 1578
(2007/10/03)
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- Indium as a reducing agent: Deprotection of 4-nitrobenzyl ethers and esters
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Indium in aqueous ethanolic ammonium chloride is an effective method for the deprotection of 4-nitrobenzyl ethers and esters.
- Moody, Christopher J.,Pitts, Michael R.
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p. 1575 - 1576
(2007/10/03)
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- STEREOSELECTIVE SYNTHESIS OF 5-ARYL-3-METHYL-2E,4E-PENTADIENALS
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A series of 5-aryl-3-methyl-2E,4E-pentadienals were synthesized stereoselectively from 4-aryl-3E-buten-2-ones and methylmagnesium iodide followed by formylation of the obtained tertiary dimethylstyrylcarbinols by the formylating complex produced from dimethylformamide and phosphorus oxychloride.A synthesis of 2,3,6-trimethyl-4-methoxybenzaldehyde, starting from pseudocumene, is proposed.
- Makin, S. M.,Mikerin, I. E.,Dobretsova, E. K.,Shavrygina, O. A.
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p. 572 - 575
(2007/10/02)
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- Preparation of and addition of carbanions to 6-methyl-6-nitrocyclohexa-2,4-dienones
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Nitration of 2-methylphenols with nitric acid and trifluoroacetic anhydride in ether at -78 deg C gives 6-methyl-6-nitrocyclohexa-2,4-dienones that can be isolated.Carbanions add to 5,6-dimethyl-6-nitrocyclohexa-2,4-dienone to give the 5-substituted 2,3-dimethyl-2-nitrocyclohex-3-enone anion, which, with additional carbanion, gives the 5-substituted 2,3-dimethylphenoxide anion by elimination of nitrous acid.Key words: nitration, dienone, addition, carbanion, nucleophilic.
- Fischer, Alfred,Henderson, George N.,Sankararaman, S.
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p. 1244 - 1246
(2007/10/02)
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- OXIDATION OF PSEUDOCUMENE IN ACETIC ACID
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The oxidation of pseudocumene in the benzene nucleus can be effected in HOAc solutions by using inorganic oxidizing agents containing oxygen, such as NaNO3, heteropolyacids, O2, Na2S2O8, and H2O2, with Pd(OAc)2 as catalyst.Na2S2O8 and H2O2 are the most ef
- Kholdeeva, O. A.,Kozhevnikov, I.V.,Sidel'nikov, V. N.,Utkin, V. A.
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p. 1903 - 1907
(2007/10/02)
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- ORTHO-METHYLATION OF PHENOLS WITH ETHYL(IODOMETHYL)ZINC
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The regioselective ortho-methylation of phenols by in situ generated ethyl(iodomethyl)zinc via an internal alkylation process is described.
- Lehnert, Erich K.,Sawyer, J. Scott,Macdonald, Timothy L.
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p. 5215 - 5218
(2007/10/02)
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- 3-OXO-α-IONOL, VOMIFOLIOL AND ROSEOSIDE IN VITIS VINIFERA FRUIT
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Key Word Index - Vitis vinifera; Vitaceae; grapes; 3-oxo-α-ionol; vomifoliol; dehydrovomifoliol; roseoside; hydrolytic studies. 3-Oxo-α-ionol, vomifoliol and dehydrovomifoliol were identified for the first time in fruit from Vitis vinifera.The last named compound was mainly present free in the juice while the others existed predominantly as conjugates.In the case of vomifoliol, the conjugation was with glucose, i.e. as roseoside.Hydrolytic studies on 3-oxo-α-ionol and vomifoliol gave a range of compounds which have been recognized as fruit and plant products.
- Strauss, Christopher R.,Wilson, Bevan,Williams, Patrick J.
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p. 1995 - 1998
(2007/10/02)
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- Die Acylierung von Acetylenen mit β,γ-ungesaettigten Saeurechloriden. Eine neue Synthese von 5-substituierten 2-Cyclopentenonen
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The acylation of acetylenes with α,α-disubstituted, β,γ-unsaturated acid chlorides under Friedel-Crafts-type conditions leads to 5-substituted 2-cyclopentenones.Phenols are formed with β,γ-unsaturated acid chlorides bearing at least one α-H-atom.These transformations are explained by the intramolecular cyclization of the initially formed vinyl cation, which, in the cases of α,α-disubstituted acid chlorides, is formed by ring contraction.The reaction leading to 2-cyclopentenones is applied to the syntesis of some spirodeca-2,6-dienones.
- Karpf, Martin
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- STUDIES ON 1-ARYLOXYSILATRANES, II. - HYDROLYTIC STABILITY OF 1-ARYLOXYSILATRANES
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The effect of substituents in the benzene ring on the rate constants of the hydrolysis of 1-aryloxysilatranes was investigated.A good correlation of log k vs. Σ? was obtained suggesting SN2-Si mechanism of the hydrolysis of all the compounds studied.The influence of the salt effect and reaction medium on the rate constant was also examined.The activation energies were determined for six compounds.
- Lukasiak, J.,Jamrogiewicz, Z.
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p. 167 - 172
(2007/10/02)
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- A DNMR STUDY OF ISOMERIC PHENOLS OBTAINED BY RING-OPENING, RING-CLOSURE OF 3-ISOPROPYL-2,4,6-TRIMETHYLPYRYLIUM SALTS: AN APPROACH TO THE REGIOSELECTIVITY OF THE RING-CLOSURE
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The regioselectivity of the syntheses of phenols via dissymmetrical pyrylium salts is found to be related to the difference in steric strain in the products as determined by conformational analysis.
- Rajoharison, Harivelo G.,Roussel, Christian,Berg, Ulf
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p. 2259 - 2262
(2007/10/02)
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- THE ACYLATION OF ACETYLENES WITH β,γ-UNSATURATED ACID CHLORIDES: A NEW SYNTHESIS OF 5,5-DISUBSTITUTED 2-CYCLOPENTENONES
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The acylation of acetylenes with α,α-disubstituted, β,γ-unsaturated acid chlorides was found to lead to 5,5-disubstituted 2-cyclopentenones by a novel intramolecular cyclization-rearrangement process.
- Karpf, Martin
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p. 4923 - 4926
(2007/10/02)
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- Polycyclic phenols, alcohols and ketones from phenols, cyclic alcohols and cyclic ketones using a nickel oxide/manganese oxide/magnesium oxide catalyst in presence of at least one of hydrogen and nitrogen
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At least one of a polycyclic phenol, a polycyclic alcohol and a polycyclic ketone is produced under hydrogenation conditions using a nickel oxide/manganese oxide/magnesium oxide catalyst by subjecting at least one of a monocyclic ketone, a monocyclic alcohol and a monocyclic phenol to said conditions and said catalyst.
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- Substituted spirocyclic derivatives
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The present invention relates to substituted spirocyclic derivatives having the general formula: STR1 wherein the dotted line represents a carbon-carbon double bond or a carbon-carbon single bond, wherein R1, R2, R3, R4, R5, and R6 are each the same or different, hydrogen or lower alkyl, wherein Z is one of the following: STR2 wherein R7 is either hydrogen or lower alkyl, wherein R8 and R9 are each lower alkyl; their methods of preparation and their use as odor-modifying ingredients in perfumes and perfumed products, and as flavor-modifying ingredients in the flavoring of foodstuffs and tobacco products.
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- Conversion of alkyl and aryl hydroxy compounds producing aldehyde, alcohol and ketone using manganese oxide/nickel oxide/magnesium oxide catalysts
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Alkyl and aryl hydroxy compounds are converted to aldehydes, alcohols, and ketones in the presence of hydrogen using a catalyst comprised of the oxides of manganese, nickel and magnesium.
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- PHENOLS FROM PYRYLIUM SALTS
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Treatment of pyrylium salts 1 and 2 with dimethylsulfonium methylide yields phenols which appear to arise from an arene oxide.
- Garst, Michael E.,Frazier, Janice D.
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- Process for the production of spirodienones and spirocyclic ketones
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This invention concerns processes for preparing compounds having the structure STR1 wherein each of R1, R2, R3, R4, R5 and R6 is the same or different and represents hydrogen or a lower alkyl group and wherein each dashed line represents a carbon-carbon single bond or a carbon-carbon double bond. Those compounds in which all three dashed lines represent carbon-carbon double bonds are prepared by reacting phenols and 2-alkylidene-1,4-disubstituted butanes. Selective reduction of these compounds yields those in which at least one dashed line represents a carbon-carbon single bond. Most of the compounds so prepared are new compounds. All are useful as fragrance materials either directly and/or in compositions and/or have useful fixative properties in fragrance compositions.
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