- Selective Activation of Unstrained C(O)-C Bond in Ketone Suzuki-Miyaura Coupling Reaction Enabled by Hydride-Transfer Strategy
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A Rh(I)-catalyzed ketone Suzuki-Miyaura coupling reaction of benzylacetone with arylboronic acid is developed. Selective C(O)-C bond activation, which employs aminopyridine as a temporary directing group and ethyl vinyl ketone as a hydride acceptor, occurs on the alkyl chain containing a β-position hydrogen. A series of acetophenone products were obtained in yields up to 75%.
- Zhong, Jing,Zhou, Wuxin,Yan, Xufei,Xia, Ying,Xiang, Haifeng,Zhou, Xiangge
-
supporting information
p. 1372 - 1377
(2022/02/23)
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- Site-Specific Oxidation of (sp3)C-C(sp3)/H Bonds by NaNO2/HCl
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A site-specific oxidation of (sp3)C-C(sp3) and (sp3)C-H bonds in aryl alkanes by the use of NaNO2/HCl was explored. The method is chemical-oxidant-free, transition-metal-free, uses water as the solvent, and proceeds under mild conditions, making it valuable and attractive to synthetic organic chemistry.
- Zhao, Jianyou,Shen, Tong,Sun, Zhihui,Wang, Nengyong,Yang, Le,Wu, Jintao,You, Huichao,Liu, Zhong-Quan
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p. 4057 - 4061
(2021/05/26)
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- Aromatization as an Impetus to Harness Ketones for Metallaphotoredox-Catalyzed Benzoylation/Benzylation of (Hetero)arenes
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Herein we report ketones as feedstock materials in radical cross-coupling reactions under Ni/photoredox dual catalysis. In this approach, simple condensation first converts ketones into prearomatic intermediates that then act as activated radical sources for cross-coupling with aryl halides. Our strategy enables the direct benzylation/benzoylation of (hetero)arenes under mild reaction conditions with high functional group tolerance.
- Chen, Ting-Wei,Cheng, Cheng-Ku,Chiu, Cheng-Chau,Huang, Pin-Gong,Lee, Shao-Chi,Lee, Yi-Hsin,Li, Li-Yun,Liao, Hsuan-Hung,Lin, Heng-Bo,Tsai, Zong-Nan,Tsao, Yong-Ting,Yang, Chung-Hsin
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supporting information
(2022/01/04)
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- Halogen-Bridged Methylnaphthyl Palladium Dimers as Versatile Catalyst Precursors in Coupling Reactions
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Halogen-bridged methylnaphthyl (MeNAP) palladium dimers are presented as multipurpose Pd-precursors, ideally suited for catalytic method development and preparative organic synthesis. By simply mixing with phosphine or carbene ligands, they are in situ converted into well-defined monoligated complexes. Their catalytic performance was benchmarked against state-of-the-art systems in challenging Buchwald–Hartwig, Heck, Suzuki and Negishi couplings, and ketone arylations. Their use enabled record-setting activities, beyond those achievable by optimization of the ligand alone. The MeNAP catalysts permit syntheses of tetra-ortho-substituted arenes and bulky anilines in near-quantitative yields at room temperature, allow mono-arylations of small ketones, and enable so far elusive cross-couplings of secondary alkyl boronic acids with aryl chlorides.
- Doppiu, Angelino,Goo?en, Lukas J.,Hu, Zhiyong,Pirkl, Nico,Sivendran, Nardana
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supporting information
p. 25151 - 25160
(2021/10/19)
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- Scalable Negishi Coupling between Organozinc Compounds and (Hetero)Aryl Bromides under Aerobic Conditions when using Bulk Water or Deep Eutectic Solvents with no Additional Ligands
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Pd-catalyzed Negishi cross-coupling reactions between organozinc compounds and (hetero)aryl bromides have been reported when using bulk water as the reaction medium in the presence of NaCl or the biodegradable choline chloride/urea eutectic mixture. Both C(sp3)-C(sp2) and C(sp2)-C(sp2) couplings have been found to proceed smoothly, with high chemoselectivity, under mild conditions (room temperature or 60 °C) in air, and in competition with protonolysis. Additional benefits include very short reaction times (20 s), good to excellent yields (up to 98 %), wide substrate scope, and the tolerance of a variety of functional groups. The proposed novel protocol is scalable, and the practicability of the method is further highlighted by an easy recycling of both the catalyst and the eutectic mixture or water.
- Dilauro, Giuseppe,Azzollini, Claudia S.,Vitale, Paola,Salomone, Antonio,Perna, Filippo M.,Capriati, Vito
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supporting information
p. 10632 - 10636
(2021/04/09)
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- Visible-light-promoted site-specific and diverse functionalization of a c(sp3)-c(sp3) bond adjacent to an arene
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We report here a strategy for inert C-C bond functionalization. Site-specific cleavage and functionalization of a saturated C(sp3)-C(sp3) bond via a visible-light-induced radical process have been achieved. The general features of this reaction are as follows. (1) Both linear and cyclic C(sp3)-C(sp3) bonds with a vicinal arene can be specifically functionalized. (2) One carbon is converted into a ketone, and another can be tunably converted into nitrile, peroxide, or halide. (3) The typical conditions include 1.0 mol % of Ru(bpy)3Cl2, 1.0 or 5.0 equiv of Zhdankin reagent, white CFL (24 W), open flask, and room temperature. These reactions offer powerful tools to modify carbon skeletons that are intractable by conventional methods. Good selectivity and functional group tolerance, together with mild and open air conditions, make these transformations valuable and attractive.
- Fang, Fang,Liu, Zhong-Quan,Sun, Minzhi,Wang, Nengyong,Wang, Yaxin,You, Huichao,Zhao, Jianyou
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p. 6603 - 6612
(2020/07/27)
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- Facile preparation of 5-alkyl-1-aryltetrazoles with arenes, acyl chlorides, hydroxylamine, and diphenylphosphoryl azide
-
Successive treatment of arenes with acyl chlorides and AlCl3, the addition of water and removal of solvent, the reaction with NH2OH?HCl and K2CO3, and the reaction with diphenylphosphoryl azide and DBU under warming conditions gave the corresponding 5-alkyl-1-aryltetrazoles efficiently in good to moderate yields. The present method is one-pot transformation of arenes into 5-alkyl-1-aryltetrazoles using the Friedel-Crafts acylation and the Beckmann rearrangement under transition-metal-free conditions.
- Shibasaki, Kaho,Togo, Hideo
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p. 1816 - 1830
(2020/11/19)
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- 1,2-Diethoxyethane catalyzed oxidative cleavage of gem-disubstituted aromatic alkenes to ketones under minimal solvent conditions
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Aerobic oxidation using pure dioxygen gas as the oxidant has attracted much attention, but its application in synthetic chemistry has been significantly hampered by the complexity of catalytic system and potential risk of high-energy dioxygen gas. By employing 1,2-diethoxyethane as a catalyst and ambient air as an oxidant, an efficient protocol for the construction of various aryl-alkyl and diaryl ketones through oxidative cleavage of gem-disubstituted aromatic alkenes under minimal solvent conditions has been achieved.
- Liu, Kai-Jian,Deng, Ji-Hui,Zeng, Tang-Yu,Chen, Xin-Jie,Huang, Ying,Cao, Zhong,Lin, Ying-Wu,He, Wei-Min
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supporting information
p. 1868 - 1872
(2020/01/31)
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- Efficient Palladium(0) supported on reduced graphene oxide for selective oxidation of olefins using graphene oxide as a ‘solid weak acid’
-
Selective oxidation of olefin derivatives to ketones has made innovative development over palladium(0) supported on reduced graphene oxide. Compared to traditional Wacker oxidation, the novel method offers an economical and environment-friendly option by using graphene oxide (GO) as a ‘solid weak acid’ instead of classical homogeneous catalysts like H2SO4 and CF3COOH. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope and transmission electron microscopy images of Pd0/RGO showed that the nanoscaled Pd particles generated at the flake structure of reduced graphene oxide. Under optimized condition, up to 44 kinds of ketones with different structures can be prepared with excellent yields.
- Gao, Xi,Zhou, Jianhao,Peng, Xinhua
-
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- One-Pot Preparation of Aromatic Amides, 4-Arylthiazoles, and 4-Arylimidazoles from Arenes
-
Simple treatment of arenes with α-bromoacetyl chloride and AlCl3, followed by the reaction with molecular iodine and aq. NH3, thioamides, or amidines gave the corresponding primary aromatic amides, 4-arylthiazoles, or 4-arylimidazoles in good yields, respectively. Aryl α-bromomethyl ketones are the key intermediates in those reactions. Primary aromatic amides were formed from arenes through the reaction of aryl α-bromomethyl ketones with molecular iodine and aq. NH3, and 4-arylthiazoles and 4-arylimidazoles were formed from arenes through the reactions of aryl α-bromomethyl ketones with thioamides and amidines, respectively, in one pot under transition-metal-free conditions.
- Yamamoto, Takahiro,Togo, Hideo
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p. 4187 - 4196
(2018/08/21)
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- Visible light promoted copper-catalyzed Markovnikov hydration of alkynes at room temperature
-
A new and efficient method for the hydration of alkynes to the corresponding ketones was successfully developed. The hydration process proceeds smoothly at room temperature with 1% mol of CuCl as catalyst under visible light irradiation. This protocol is applicable to various alkynes, including aromatic alkynes, polycyclic aromatic and heterocyclic aromatic excellent regioselectivity in good to excellent yields.
- Niu, Teng-fei,Jiang, Ding-yun,Li, Si-yuan,Shu, Xing-ge,Li, Huan,Zhang, Ai-ling,Xu, Jia-yu,Ni, Bang-qing
-
supporting information
p. 1156 - 1159
(2017/03/02)
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- Selective Oxidation of Styrene Derivatives to Ketones over Palladium(0)/Carbon with Hydrogen Peroxide as the Sole Oxidant
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Pd0/C catalyst exhibited excellent catalytic activity in the Wacker oxidation of styrene derivatives to corresponding ketones with hydrogen peroxide as a clean oxidant. Compared with the conventional Wacker system, the newly developed method offers a cost-efficient and environmentally friendly option without the use of a copper salt as a co-catalyst.
- Xia, Xiaomeng,Gao, Xi,Xu, Junhui,Hu, Chuanfeng,Peng, Xinhua
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supporting information
p. 607 - 610
(2017/03/11)
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- 5-Aryl-1H-pyrazole-3-carboxylic acids as selective inhibitors of human carbonic anhydrases IX and XII
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Inhibitory activity of a congeneric set of 23 phenyl-substituted 5-phenyl-pyrazole-3-carboxylic acids toward human carbonic anhydrase (hCA, EC 4.2.1.1) isoforms I, II, IX and XII was evaluated by a stopped-flow CO2 hydrase assay. These compounds exerted a clear, selective inhibition of hCA IX and XII over hCAI and II, with Ki in two to one digit micromolar concentrations (4-50 μM). Derivatives bearing bulkier substituents in para-position of the phenyl ring inhibited hCA XII at one-digit micromolar concentrations, while derivatives having alkyl substituents in both ortho- and meta-positions inhibited hCA IX with Kis ranging between 5 and 25 μM. Results of docking experiments offered a rational explanation on the selectivity of these compounds toward CA IX and XII, as well as on the substitution patterns leading to best CA IX or CA XII inhibitors. By examining the active sites of these four isoforms with GRID generated molecular-interaction fields, striking differences between hCA XII and the other three isoforms were observed. The field of hydrophobic probe (DRY) appeared significantly different in CA XII active site, comparing to other three isoforms studied. To the best of our knowledge such an observation was not reported in literature so far. Considering the selectivity of these carboxylates towards membrane-associated over cytosolic CA isoforms, the title compounds could be useful for the development of isoform-specific non-sulfonamide CA inhibitors.
- Cvijeti?, Ilija N.,Tan?, Muhammet,Jurani?, Ivan O.,Verbi?, Tatjana ?.,Supuran, Claudiu T.,Drakuli?, Branko J.
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p. 4649 - 4659
(2015/08/03)
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- Green photocatalytic organic transformations by polyoxometalates vs. mesoporous TiO2 nanoparticles: Selective aerobic oxidation of alcohols
-
In this study, the catalytic activity of decatungstate (W10O324-) supported on mesoporous TiO2 nanoparticle assemblies (DT-MTA) was compared with that of homogeneous [Bu4N]4W10O32 catalysts under mild conditions. Our experiments showed that both catalytic systems achieve exceptionally high activity and selectivity under UV-visible light oxidation of various para-substituted aryl alcohols, using molecular oxygen as a "green" oxidant. The chemoselective transformation of aryl alcohols into the corresponding ketones was investigated with gas chromatography (GC) and NMR spectroscopy. Product analysis and kinetic results also indicated that these photooxidation reactions proceed via both electron transfer (ET) and hydrogen atom transfer (HAT) mechanisms over the DT-MTA catalyst, with the former one as the predominant, whereas a HAT route was adopted to account for the decatungstate homogeneous catalyzed reactions. This journal is
- Symeonidis, Theodoros S.,Tamiolakis, Ioannis,Armatas, Gerasimos S.,Lykakis, Ioannis N.
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p. 563 - 568
(2015/03/14)
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- Design, synthesis and pharmacology of 1,1-bistrifluoromethylcarbinol derivatives as liver X receptor β-selective agonists
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A novel series of 1,3-bistrifluoromethylcarbinol derivatives that act as liver X receptor (LXR) β-selective agonists was discovered. Structure-activity relationship studies led to the identification of molecule 62, which was more effective (Emax) and selective toward LXRβ than T0901317 and GW3965. Furthermore, 62 decreased LDL-C without elevating the plasma TG level and significantly suppressed the lipid-accumulation area in the aortic arch in a Bio F1B hamster fed a diet high in fat and cholesterol. We demonstrated that our LXRβ agonist would be potentially useful as a hypolipidemic and anti-atherosclerotic agent. In this manuscript, we report the design, synthesis and pharmacology of 1,3-bistrifluoromethylcarbinol derivatives.
- Koura, Minoru,Matsuda, Takayuki,Okuda, Ayumu,Watanabe, Yuichiro,Yamaguchi, Yuki,Kurobuchi, Sayaka,Matsumoto, Yuuki,Shibuya, Kimiyuki
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p. 2668 - 2674
(2015/06/08)
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- Simultaneous identification of Fenton degradation by-products of diclofenac, ibuprofen and ketoprofen in aquatic media by comprehensive two-dimensional gas chromatography coupled with mass spectrometry
-
Diclofenac, ibuprofen and ketoprofen are anti-inflammatory drugs intensively used both in human and animal treatment. Due to their high stability these compounds are partially removed by wastewater treatment plants and from this reason the development of some alternative treatments such as advanced oxidative processes are necessary. The main problems in the optimization of an advanced oxidative process rise from the difficulties which appear in the identification of degradation by-products necessary for the establishment of degradation pathway. In this paper a developed method for the simultaneous identification of Fenton degradation by-products of the three above mentioned pharmaceuticals is presented. The obtained results show the comprehensive two-dimensional gas chromatography coupled with mass spectrometry as a proper method for the analysis of the complex mixture of compounds resulted from the Fenton degradation process. Moreover, some compounds never mentioned in the scientific literature were identified. (Chemical Equation Presented).
- Beldean-Galea, Mihail Simion,Coman, Virginia,Copaciu, Florina,Thiébaut, Didier,Vial, Jér?me
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p. 1021 - 1027
(2015/07/15)
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- Tetra-n-butylammonium bromide: A simple but efficient organocatalyst for alcohol oxidation under mild conditions
-
A simple but efficient organocatalytic system with 5 mol% tetra-n-butylammonium bromide (TBAB) as the catalyst has been identified for alcohol oxidation for the first time. This organocatalytic system is compatible with a broad range of benzylic/allylic alcohols with various catalytically reactive groups. Besides, it shows excellent selectivity for secondary benzylic alcohols over aliphatic alcohols, and good selectivity over the primary benzylic alcohol site in 4-(1-hydroxyethyl)benzyl alcohol. Thus, the features of simplicity, high efficiency, selectivity and mildness of reaction conditions associated with this TBAB organocatalytic system suggest its potential for widespread use in synthetic chemistry.
- Ma, Xinyi,Li, Zhongfeng,Liu, Feijie,Cao, Shengli,Rao, Honghua
-
supporting information
p. 1741 - 1746
(2014/06/09)
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- Highly selective Wacker reaction of styrene derivatives: A green and efficient aerobic oxidative process promoted by benzoquinone/NaNO 2/HClO4 under mild conditions
-
A green and efficient catalytic redox system for the aerobic oxidative Wacker oxidation of styrene derivatives at room temperature using molecular oxygen as the terminal oxidant without copper chloride has been developed. The newly developed system exhibited excellent catalytic activity for the smooth transformation of terminal styrene derivatives to the desired methyl ketones with up to 96% yield and >99% selectivity. The Royal Society of Chemistry 2013.
- Zhang, Guofu,Xie, Xiaoqiang,Wang, Yong,Wen, Xin,Zhao, Yun,Ding, Chengrong
-
supporting information
p. 2947 - 2950
(2013/07/25)
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- Direct synthesis of water-tolerant alkyl indium reagents and their application in palladium-catalyzed couplings with aryl halides
-
A direct result: Alkyl indium reagents are synthesized by the insertion of indium into alkyl halide mediated by CuCl. The synthetic utility of these reagents is demonstrated by their palladium-catalyzed coupling with aryl halides (see scheme). The reagents are compatible with various functional groups, and this makes the protocol generally useful in organic synthesis. DMA=N,N-dimethylacetamide, TBS=tert-butyldimethylsilyl.
- Shen, Zhi-Liang,Goh, Kelvin Kau Kiat,Yang, Yong-Sheng,Lai, Yin-Chang,Wong, Colin Hong An,Cheong, Hao-Lun,Loh, Teck-Peng
-
supporting information; experimental part
p. 511 - 514
(2011/03/17)
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- Negishi cross-coupling of secondary alkylzinc halides with aryl/heteroaryl halides using Pd-PEPPSI-IPent
-
Pd-PEPPSI-IPent has proven to be an excellent catalyst for the Negishi cross-coupling reaction of secondary alkylzinc reagents with a wide variety of aryl/heteroaryl halides. Importantly, β-hydride elimination/migratory insertion of the organometallic leading to the production of isomeric coupling products has been significantly reduced using the highly-hindered Ipent ligand.
- Alimsiz, Seluk,Organ, Michael G.
-
supporting information; experimental part
p. 5181 - 5183
(2011/06/09)
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- Catalytic Friedel-Crafts acylation and benzoylation of aromatic compounds using activated hematite as a novel heterogeneous catalyst
-
Catalytic Friedel-Crafts acylation of benzene and unactivated benzenes such as chlorobenzene and nitrobenzene have been successfully carried out using activated hematite (α-Fe2O3) as a new, heterogeneous and green catalyst. Sonication of neat α-Fe2O3 in a water bath under air atmosphere at room temperature followed by heating at 200°C, dramatically increase the activity of α-Fe2O 3. With the catalyst loading as low as 5.0mol%, a wide variety of benzene derivatives were easily converted into the corresponding acylated products in a clean and high-yielding acylation reaction. It was found that the activated α-Fe2O3 could be efficiently recycled and reused several times by simple washing with ethyl acetate, this cannot be attained with most of the traditional catalysts. Copyright
- Sharghi, Hashem,Jokar, Mahboubeh,Doroodmand, Mohammad Mahdi,Khalifeh, Reza
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experimental part
p. 3031 - 3044
(2011/02/21)
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- Cross-coupling reactions through the intramolecular activation of Alkyl(triorgano)silanes
-
(Figure Presented) Cross-Si-ing the Jordan: Cross-coupling reactions of 2-(2-hydroxyprop-2-yl)phenylsubstituted alkylsilanes with a variety of aryl halides proceed in the presence of palladium and copper catalysts. The use of K3PO4 base allows for highly chemoselective alkyl coupling with both primary and secondary alkyl groups (Alk).
- Nakao, Yoshiaki,Takeda, Masahide,Matsumoto, Takuya,Hiyama, Tamejiro
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supporting information; scheme or table
p. 4447 - 4450
(2010/08/19)
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- Aerobic oxidation of benzylic halides to carbonyl compounds with molecular oxygen catalyzed by tempo/kno2 in aqueous media
-
Benzylic halides were successfully oxidized to the corresponding aldehydes and ketones in good to excellent yields in aqueous media with molecular oxygen as oxidant in the presence of catalytic amounts of TEMPO (2,2,6,6- tetramethylpiperidyl-1-oxy) and potassium nitrite (KNO2).
- Liu, Qifa,Lu, Ming,Yang, Fei,Wei, Wei,Sun, Feng,Yang, Zhenbang,Huang, Sufeng
-
scheme or table
p. 1106 - 1114
(2010/04/29)
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- Decatungstate catalyst supported on silica and γ-alumina: Efficient photocatalytic oxidation of benzyl alcohols
-
Four supported catalysts with the same tungsten loading were prepared by depositing decatungstate species W10O4-32, through wet impregnation, on the surface of γ-alumina and silica at different pH values. The prepared samples were characterized using BET measurements as well as XRD, UV-vis DR, and XP spectroscopies. Higher dispersion of W(VI) oxo-species was obtained in the silica-supported catalysts compared with the corresponding alumina-supported ones. Within the same support, the dispersion was higher when the impregnation pH is lower than the point of zero charge (pzc) of the support. The decatungstate anions were present mainly on the silica surface without any modification, whereas these underwent a partial depolymerization on their deposition on the γ-alumina surface. The extent of depolymerization was less in the sample prepared at pH above pzc. These findings were explained in terms of the mode of deposition of the W(VI) species from the solution onto the support surface. The photocatalytic activity of the aforementioned catalysts, concerning the photooxidation of 1-phenylethanol, depends on the fraction of the W10O4-32 supported species rather than on the W(VI) dispersion. Thus, extremely high conversions have been obtained over the silica-based catalysts and also over the γ-alumina-based catalyst prepared at relatively high pH. These catalysts also are very effective in the photooxidation of a series of secondary and primary benzyl alcohols, in which benzyl ketones and benzoic acids were formed as the only or major products, respectively. The easy separation of the solid catalyst from the reaction mixture, the high activity, selectivity, and stability as well as the retained activity in subsequent catalytic cycles, make these supported catalysts suitable for a small-scale synthesis. Based on product analysis and kinetic data on the heterogeneous oxidation of benzyl alcohols, we suggest that a hydrogen abstraction transfer (HAT) mechanism predominates with respect to an electron transfer (ET) one in these reactions.
- Tzirakis, Manolis D.,Lykakis, Ioannis N.,Panagiotou, George D.,Bourikas, Kyriakos,Lycourghiotis, Alexis,Kordulis, Christos,Orfanopoulos, Michael
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p. 178 - 189
(2008/09/18)
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- 9,10-Dicyanoanthracene photosensitized oxidation of aryl alkanols: Evidence for an electron transfer mechanism
-
9,10-Dicyanoanthracene (DCA) photosensitizes the oxidation of a series of para substituted aryl alkanols in oxygen-saturated acetonitrile. Product analysis and Hammett correlations support an electron transfer mechanism for the title reaction.
- Lykakis, Ioannis N.,Lestakis, Stellios,Orfanopoulos, Michael
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p. 6247 - 6251
(2007/10/03)
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- Resolution of methylarylmethanols via oxidation with Nocardia corallina
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Ten different racemates of methylarylmethanols were subjected to whole cells of Nocardia corallina B-276 to give, via enantioselective oxidations, the corresponding ketone and the enantiomerically enriched secondary alcohol in moderate yields and excellent e.e.s. The configuration of the resulting alcohol is (R). This procedure permits a very good separation of the racemates of meta- and para-monosubstituted methylarylmethanols.
- Perez, Herminia I.,Luna, Hector,Manjarrez, Norberto,Solis, Aida
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p. 1709 - 1712
(2007/10/03)
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- Tetrabutylammonium peroxydisulfate in organic synthesis; IV. An efficient, highly selective and oxidative deoximation by tetrabutylammonium peroxydisulfate
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Tetrabutylammonium peroxydisulfate has been proved out to be an efficient and highly chemoselective reagent for the conversion of oximes to the corresponding carbonyl compounds under mild conditions.
- Chen, Fener,Liu, Anchang,Yan, Qiongjiao,Liu, Mingxing,Zhang, Daoming,Shao, Lanying
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p. 1049 - 1056
(2007/10/03)
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- Wacker oxidation of alkenes using a fluorous biphasic system. A mild preparation of polyfunctional ketones
-
Various alkenes are oxidized to the corresponding ketones using t-BuOOH in the presence of a palladium(II) catalyst bearing perfluorinated ligands using a biphasic solvent system of benzene and bromoperfluorooctane.
- Betzemeier, Bodo,Lhermitte, Frederic,Knochel, Paul
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p. 6667 - 6670
(2007/10/03)
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- Chromium-Pillared Clay as a Catalyst for Benzylic Oxidation and Oxidative Deprotection of Benzyl Ethers and Benzylamines: A Simple and Convenient Procedure
-
A mild and efficient method for benzylic oxidation of arylmethylenes to the corresponding carbonyl compounds in good yields is described using a catalytic amount of chromium-pillared montmorillonite and equimolar quantities of tert-butyl hydroperoxide.The method is very selective toward monocarbonyl compounds of the substrates prone to form dicarbonyl compounds.The present heterogeneous catalyst is inert toward the branched hydrocarbone and has been put to practice to obtain p-isobutylacetophenone selectively from p-isobutylethylbenzene.Further, the method is extended successfully to the oxidative debenzylation reactions for the first time.A striking feature of the oxidative deprotection with the present method is the deprotection of a benzyl group from the substrates having any alkyne moiety.
- Choudary, Boyapati M.,Prasad, Annavajhula Durga,Bhuma, Vendantam,Swapna, Vinukonda
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p. 5841 - 5844
(2007/10/02)
-
- FLASH VACUUM THERMOLYSIS OF DISPIROALKADIENES
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The Flash Vacuum Thermolysis (FVT) of dispirotetradeca -4,13-diene (7a). dispirotrideca-4,12-diene (7b) and dispirodeca-4,9-diene (7e) at 500-750 deg C is reported.The complicated reaction mixture from 7a and 7b (Scheme 3) included at lower temperatures vinylspiroalkadienes 9, ethylidenespiroalkadiene 10b, β-ethylcycloalkabenzenes 11, while at higher temperatures, p-n-alkyl-(5) and p-sec-alkylstyrenes 14 and p-divinylbenzene (15) dominated.Product formation is explained by invoking diradicals 8,6 and 12 as well as the cyclophanes 1 and 13 as intermediates.For 7e, the product mixture was less complicated and consisted of p-ethylstyrene (5e), 15 and, unexpectedly,p-isopropylstyrene (14e) which contains one carbon more than the starting material.The analysis and interpretation of product formation largely confirms previously suggested reaction pathways and furnishes further interesting details.However, new and unexpected features are also encountered, especially in the fragmentations of 1 and 13 which may stimulate future investigations on the thermal behaviour of these relatively simple hydrocarbons.
- Kraakmann, P. A.,Nibbering, E. T. J.,Wolf, W. H. de,Bickelhaupt, F.
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p. 5109 - 5124
(2007/10/02)
-
- Enamines; 44. 2-Acyl-1,1-diamino-ethenes. A New Source of Methylketones, β-Keto Amides and β-Keto Esters
-
A general synthesis of 2-acyl-1,1-diamino-ethenes by reaction of 1,1-dimorpholino- and 1,1-dipiperidino-ethenes with aliphatic and aromatic acyl chlorides and their utilization as a source of methylketones, β-keto amides and β-keto esters is reported.
- Armati, Antonella,Ruggieri, Pietro De,Rossi, Elisabetta,Stradi, Riccardo
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p. 573 - 576
(2007/10/02)
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- Substituent effects on benzyl radical hyperfine coupling (hfc) constants. Part 3. Comparison of the α-hfc for substituted benzyl radicals with the β-hfc for substituted cumyl radicals
-
The electron spin resonance (esr) spectra of eighteen para-substituted cumyl radicals were analyzed.The relationship between the β-hyperfine coupling (β-hfc) constants of these cumyl radicals and the corresponding α-hfc constants of benzyl radicals was studied.Although there is a general trend for the α- and β-hfc values to vary in a similar manner, specific deviations from a linear correlation between these parameters were observed.These deviations were rationalized by considering charge effects on spin delocalization.The correlation coefficient for the linear regression analysis of these α- and β-hfc values was found to significantly improve when parameters reflecting charge effects on spin delocalization were included in an extended Hammett treatment of the spectral data.
- Arnold, Donald R.,Nicholas, A. Martin de P.,Snow, Miles S.
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p. 1150 - 1156
(2007/10/02)
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- A Facile Displacement of Tertiary Nitro Group by Hydrogen with Sodium Hydrogentelluride
-
Sodium hydrogentelluride is a useful reagent for replacement of a class of tertiary nitro group by hydrogen.
- Suzuki, Hitomi,Takaoka, Koji,Osuka, Atsuhiro
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p. 1067 - 1068
(2007/10/02)
-
