- Synthesis of Ti-Al binary oxides and their catalytic application for C-H halogenation of phenols, aldehydes and ketones
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Traditional C–H halogenation of organic compounds often requires corrosive agent or harsh condition, and current researches are focused on the use of noble metals as catalyst. In order to give an efficient, benign, activity-adjustable and cost-effective system for halogenation, a series of Ti-Al mixed oxides are prepared as catalyst through sol-gel in this work. Characterizations reveal all catalysts contain more aluminum than titanium, but preparative conditions affect their composition and crystallinity. Monitoring of particle size, zeta potential and UV–vis of preparative solution reveals that formation of catalyst colloids undergoes chemical reaction, affecting catalyst morphology. In halogenation, all catalysts show moderate to high activities, copper chloride proves to be an effective halogen source rather than sodium chloride. The chlorination and bromination are better than iodization, phenol and ketone appear to be more appropriate substrates than aldehyde. Additionally, oxide backbone of catalyst is more durable than its organic components during recycling. This study may provide new catalytic materials for progress of C–H activation.
- Su, Peigen,Fan, Chao,Yu, Heng,Wang, Wanqin,Jia, Xin,Rao, Qifan,Fu, Chenxi,Zhang, Donghua,Huang, Benhua,Pan, Cheng,Zheng, Aqun,Sun, Yang
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- STABILIZER FOR ORGANIC MATERIALS
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The present invention provides a compound represented by the formula (I): wherein R1-R4 are each independently a t-butyl group or a t-pentyl group.
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Paragraph 0091
(2018/07/31)
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- Synthesis and oxidizing ability of p-chloranil dimer
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A p-chloranil dimer ( pCh2) has been synthesized. The first reduction potential of pCh2 shifted to a more positive value than that observed for the p-chloranil monomer ( pCh1) and was more negative than that for 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ). As expected, pCh2 oxidized 9,10-dihydroanthracene and α-tetralol to give anthracene and α-tetralone, respectively, more efficiently than pCh1 did. The advantages of pCh2 were observed in oxidations of 2,4-di-tert-butylphenol and 2,6-di-tertbutyl- 4-methylphenol. Although further oxidation took place in DDQ oxidations and no reaction occurred in pCh1 oxidations, initial oxidation products were solely obtained in pCh2 oxidation because of its moderate oxidizing ability.
- Hayashi, Naoto,Nakagawa, Hiroyuki,Sugiyama, Yuko,Yoshino, Junro,Higuchi, Hiroyuki
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p. 398 - 400
(2013/05/21)
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- Mechanism of dimerization-rearrangement of organosilicon aroxyls
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Organosilicon aroxyls form disiloxyhiaryls via C-C dimerization with simultaneous (or subsequent) isomerization of the dimeric intermediate, involving migration of the ortho-organosilyl substituents from carbon to oxygen.
- Muslin,Lyapina,Tyulina,Khorshev,Vavilina
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p. 1248 - 1251
(2007/10/03)
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- Cyclodienones. X. Reaction of Halo-cyclohexadien-1-ones with Phenols in the Presence of α-Picoline and Preparation of 4-Hydroxy- and 2-Hydroxyphenyl Aryl Ethers
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Reaction of 4-halocyclohexadienones such as 4-bromo-(1a), 4-chloro-2,4,6-tri-t-butyl-(1b), 2,4-dichloro-4,6-di-t-butyl-2,5-cyclohexadien-1-one, and 2,4-dichloro-2,6-di-t-butyl-3,5-cyclohexadien-1-one with phenols in the presence of α-picoline was carried out under various conditions.The reaction of 1a and 1b with phenols afforded the corresponding 2-aryloxy-4,6-di-t-butyl phenols together with various by-products.The AlCl3 catalyzed trans-t-butylation of 2-aroxy-4,6-di-t-butyl-phenols, which were obtained by the above reaction, afforded the corresponding 2-hydroxyphenyl aryl ethers.The similar reaction of 4-aroxy-2,4,6-tri-t-butyl-2,5-cyclohexadien-1-ones also afforded the corresponding 4-hydroxyphenyl aryl ethers.
- Tashiro, Masashi,Itoh, Takashi,Fukata, Gouki
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p. 416 - 420
(2007/10/02)
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- CYCLODIENONES. 9. REACTION 4-HALO-2,4,6-TRI-TERT-BUTYL-2,5-CYCLOHEXADIEN-1-ONES WITH PYRAZOLES AND PREPARATION OF 1-(2-HYDROXYPHENYL)- AND 1-(4-HYDROXYPHENYL)PYRAZOLES
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Reaction of 4-halo-2,4,6-tri-tert-butyl-2,5-cyclohexadien-1-one (1) with pyrazoles (8) afforded 4-(pyrazol-1-yl)-2,4,6-tri-tert-butyl-2,5-cyclohexadien-1-ones (9), 1-(4-hydroxy-3,5-di-tert-butylphenyl)- and 1-(2-hydroxy-3,5-di-tert-butylphenyl)pyrazoles (10 and 11) together with by-products.De-tert-butylation of 9, 10 and 11 was carried out in boiling 85percent H3PO4 to give the corresponding 1-(4-hydroxyphenyl)- and 1-(2-hydroxyphenyl)pyrazoles (17 and 18) in good yields, respectively.
- Fukata, Guouki,Itoh, Takashi,Tashiro, Masashi
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p. 1487 - 1495
(2007/10/02)
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- Cyclodienones. 7. Preparation and Reduction of 1-(3,5-Di-tert-butyl-2-hydroxyphenyl)pyridinium Halides
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The reactions of 4-bromo- (1a) and 4-chloro-2,4,6-tri-tert-butyl-2,5-cyclohexadien-1-one (1b) with compounds such as pyridine (4a), α- (4b), β- (4c), and γ-picoline (4d), and 3,5-lutidine (4e) were carried out under various conditions to produce the corresponding 1-(3,5-di-tert-butyl-2-hydroxyphenyl)pyridinium halides (7) or their intramolecular salts (8).The reduction of 7 and 8 with NaBH4 in methanol afforded in good yields the corresponding tetrahydropyridine derivatives (21), which were reduced to o-piperidinophenols (22) by hydrogenation with Raney Ni (W2) catalyst in high yields.The reaction pathway of the formation of 7 is also discussed.
- Fukata, Gouki,Itoh, Takashi,Tashiro, Masashi
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p. 4454 - 4458
(2007/10/02)
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- CYCLOHEXADIENONES. 5. REACTION OF 4-HALO-2,4,6-TRI-t-BUTYL-2,5-CYCLOHEXADIEN-1-ONES WITH IMIDAZOLES
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Reactions of 4-bromo- (1a) and 4-chloro-2,4,6-tri-t-butyl-2,5-cyclohexadien-1-one (1b) with imidazole (6b), 1-methyl- (6a), 2-methyl- (6c), 4-methylimidazole (6d), benzimidazole (6e), and 2-methylbenzimidazole (6f) was carried out under various conditions.It was found in these reactions that many products such as the 1-(4-oxo-2,5-cyclohexadienyl)-, 1-(2-hydroxyphenyl)- and 1-(4-hydroxyphenyl)imidazoles were formed and that the type of the products depended upon the structures of imidazoles 6.
- Fukata, Gouki,Itoh, Takashi,Tashiro, Masashi
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p. 549 - 554
(2007/10/02)
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- Selective Preparation. 31. Oxidative Coupling of 2-Halo-4,6-di-tert-butylphenols with Potassium Hexacyanoferrate (III) in Benzene
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When 2-bromo-4,6-di-tert-butylphenol (1b) was treated with K3Fe(CN)6 in benzene, 1,4-dihydro-4-bromo-2,4,6,8-tetra-tert-butyl-1-oxodibenzofuran (3) was obtained in 81percent yield together with a small amount of 2,4,6,8-tetra-tert-butyldibenzofuran (4).Heating of 3 in primary alcohols such as methanol and ethanol afforded the corresponding 1,4-dihydro-4-alkoxy-2,4,6,8-tetra-tert-butyl-1-oxodibenzofuran (9) in good yields.However, treatment of 3 with boiling isopropyl alcohol gave in 85percent yield 1-hydroxy-2,4,6,8-tetra-tert-butyldibenzofuran (5), which afforded 1-hydroxydibenzofuran (6) by its AlCl3-catalyzed trans tert-butylation in toluene.Compound 6 was obtained also by the AlCl3-catalyzed trans alkylation of 3.Similar trans alkylation of 4 afforded dibenzofuran (19). 1-Hydroxy-4-methoxy- (11) and 1,4-dihydro-1,4-dioxo-2,6,8-tri-tert-butyldibenzofuran (12) were also prepared from compound 3.Similar oxidation of 2-chloro-4,6-di-tert-butylphenol (1c) afforded 6,6'-bis (22) and 2,4-di-tert-butyl-4-chloro-6-(2,4-di-tert-butyl-6-chlorophenoxy)-cyclohexa-2,5-dien-1-one (23) in 23percent and 53percent yields, respectively.However, oxidation of 2-fluoro-4,6-di-tert-butylphenol (1d) gave only one product, 2,4-di-tert-butyl-4-fluoro-6-(2,4-di-tert-butyl-6-fluorophenoxy)-cyclohexa-2,5-dien-1-one (36), in 63percent yield.The mechanisms of oxidation of 2-halo-4,6-di-tert-butylphenols with K3Fe(CN)6 in benzene were also discussed in this paper.
- Tashiro, Masashi,Yoshiya, Haruo,Fukata, Gouki
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p. 3784 - 3789
(2007/10/02)
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- Reactions of some substituted phenols with chromyl and vanadyl chlorides
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The oxidation of 2,4,6-tritertbutylphenol and several other alkyl and halophenols by CrO2Cl2 and VOCl3 was studied.The products of CrO2Cl2 oxidation are mostly quinones and diphenoquinones, whilst those of VOCl3 oxidation also include major amounts of dealkylated phenols and C-C coupled dimers.The product distributions are interpreted in terms of a mechanism involving phenoxyl radicals, ligand transfer from metal to radical, and either phenoxonium ions or metallate esters where there is sufficient electron withdrawal from the organic group for it to exhibit carbenium ion properties.The differences in behaviour between CrO2Cl2, VOCl3, and CuCl2 are attributed to different balances between the oxidation potential and Lewis acidity of the metal complexes.It is concluded that CrO2Cl2 is not a good model for proposed ferryl intermediate in heme oxidase systems since it induces 1 --> 3 rather than 1 --> 2 halogen shifts and an NIH shift that is best explained by carbenium ion-like intermediates.
- Harrod, John F.,Pathak, Asha
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p. 686 - 693
(2007/10/02)
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