- Relay Catalysis by Achiral Borane and Chiral Phosphoric Acid in the Metal-Free Asymmetric Hydrogenation of Chromones
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A strategy of relay catalysis by achiral borane and chiral phosphoric acid was successfully developed for the asymmetric hydrogenation of chromones, giving the desired products in high yields with up to 95% ee. Achiral borane and chiral phosphoric acid are highly compatible in this reaction. The achiral borane acts as a Lewis acid for the first-step hydrogenation, and the chiral phosphoric acid acts as an effective chiral proton shuttle to control the enantioselectivity.
- Chen, Jingjing,Gao, Bochao,Feng, Xiangqing,Meng, Wei,Du, Haifeng
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supporting information
p. 8565 - 8569
(2021/11/13)
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- Photoredox/nickel-catalyzed hydroacylation of ethylene with aromatic acids
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We report a general, practical and scalable hydroacylation reaction of ethylene with aromatic carboxylic acids with the synergistic combination of nickel and photoredox catalysis. Under ambient temperature and pressure, feedstock chemicals such as ethylene can be converted into high-value-added aromatic ketones in moderate to good yields (up to 92%) with reaction time of 2-6 hours.
- Chen, Shuai,He, Hengchi,Li, Weipeng,Xie, Jin,Zhang, Lili,Zhu, Chengjian
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supporting information
p. 9064 - 9067
(2021/09/15)
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- Rhoda-Electrocatalyzed Bimetallic C?H Oxygenation by Weak O-Coordination
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Rhodium-electrocatalyzed arene C?H oxygenation by weakly O-coordinating amides and ketones have been established by bimetallic electrocatalysis. Likewise, diverse dihydrooxazinones were selectively accessed by the judicious choice of current, enabling twofold C?H functionalization. Detailed mechanistic studies by experiment, mass spectroscopy and cyclovoltammetric analysis provided support for an unprecedented electrooxidation-induced C?H activation by a bimetallic rhodium catalysis manifold.
- Tan, Xuefeng,Massignan, Leonardo,Hou, Xiaoyan,Frey, Johanna,Oliveira, Jo?o C. A.,Hussain, Masoom Nasiha,Ackermann, Lutz
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supporting information
p. 13264 - 13270
(2021/05/06)
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- C?H Oxygenation Reactions Enabled by Dual Catalysis with Electrogenerated Hypervalent Iodine Species and Ruthenium Complexes
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The catalytic generation of hypervalent iodine(III) reagents by anodic electrooxidation was orchestrated towards an unprecedented electrocatalytic C?H oxygenation of weakly coordinating aromatic amides and ketones. Thus, catalytic quantities of iodoarenes in concert with catalytic amounts of ruthenium(II) complexes set the stage for versatile C?H activations with ample scope and high functional group tolerance. Detailed mechanistic studies by experiment and computation substantiate the role of the iodoarene as the electrochemically relevant species towards C?H oxygenations with electricity as a sustainable oxidant and molecular hydrogen as the sole by-product. para-Selective C?H oxygenations likewise proved viable in the absence of directing groups.
- Massignan, Leonardo,Tan, Xuefeng,Meyer, Tjark H.,Kuniyil, Rositha,Messinis, Antonis M.,Ackermann, Lutz
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supporting information
p. 3184 - 3189
(2020/01/24)
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- The insertion of arynes into the O-H bond of aliphatic carboxylic acids
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The insertion of arynes into the O-H bond of aliphatic carboxylic acids promoted by sodium carboxylates is described. The reactions led to the formation of aryl carboxylates in good yields with good chemoselectivities under mild conditions.
- Wen, Chunxiao,Chen, Qian,He, Zhenwen,Yan, Xinxing,Zhang, Changyuan,Du, Zhiyun,Zhang, Kun
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supporting information
p. 5470 - 5473
(2015/09/15)
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- Lithiation of a silyl ether: Formation of an ortho-fries hydroxyketone
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A hydroxy-directed alkylation of an N,N-diethylarylamide using CIPE-assisted α-silyl carbanions (CIPE=complex-induced proximity effect) has been developed using a simple reagent combination of LDA (lithium diisopropylamide) and chlorosilane. A study of the mechanism, and the application of the procedure to an anionic Snieckus-Fries rearrangement for a highly efficient synthesis of the potent phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002, are reported.
- Lo, Hong-Jay,Lin, Chin-Yin,Tseng, Mei-Chun,Chein, Rong-Jie
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supporting information
p. 9026 - 9029
(2014/09/17)
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- Broadening the catalyst and reaction scope of regio- and chemoselective C-H oxygenation: A convenient and scalable approach to 2-acylphenols by intriguing Rh(ii) and Ru(ii) catalysis
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A unique Rh(ii) and Ru(ii) catalyzed C-H oxygenation of aryl ketones and other arenes has been developed for the facile synthesis of diverse functionalized phenols. The reaction demonstrates excellent reactivity, regio- and chemoselectivity, good functional group compatibility and high yields. The practicality of this method has been proved by gram-scale synthesis of a few different 2-acylphenols. Its utility has been well exemplified in further applications in heterocycle synthesis and direct modifications of drug Fenofibrate.
- Shan, Gang,Han, Xuesong,Lin, Yun,Yu, Shanyou,Rao, Yu
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supporting information
p. 2318 - 2322
(2013/04/10)
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- Synthesis of ortho-acylphenols through the palladium-catalyzed ketone-directed hydroxylation of arenes
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ortho-Acylphenols are an important structural motif found in a diversity of bioactive molecules ranging from natural products to drugs (Figure 1). Moreover, they also serve as versatile building blocks for the synthesis of various pharmaceuticals, such as warfarin, as well as agrichemicals, flavors, and fragrances. Classic approaches to the synthesis of o-acylphenols generally involve a two-step process: acylation of phenols followed by Fries rearrangement of the resulting phenyl esters (Scheme 1a). On the other hand, direct C-acylation of phenols has also been known under more forcing conditions. Although effective, these approaches are often complicated by the formation of undesired p-substituted products when bulky acyl groups need to be introduced, as well as the limited variety of ketones that can be generated.
- Mo, Fanyang,Trzepkowski, Louis J.,Dong, Guangbin
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supporting information
p. 13075 - 13079
(2013/02/25)
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- Pd-catalyzed C-H oxygenation with TFA/TFAA: Expedient access to oxygen-containing heterocycles and late-stage drug modification
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Functionalized phenols are valuable industrial chemicals related to pharmaceuticals, agrochemicals, and polymers. Therefore, the direct catalytic hydroxylation of arenes to produce phenols has attracted much attention. Although tremendous progress has been made in this field, there are still difficult substrates which remain unmet challenges for direct hydroxylation in terms of regio- and chemoselectivity, as well as the practicality of current methods (Scheme 1). For example, 2-hydroxy aromatic ketones are useful synthetic intermediates for the preparation of various oxygen-containing heterocycles such as benzofuranone, chromanone, benzoxazole, and dibenzooxazepine; they also serve as key building blocks for drugs such as celiprolol, acebutolol, and propafenone. Traditional strategies for accessing 2-hydroxy aromatic ketones have mainly involved the oxidation of benzylic alcohols, the hydrolysis of aromatic halides, Fries rearrangement of esters or the demethylation of methyl phenyl ether. These methods generally suffer from one limitation or another, such as tedious reaction procedures, harsh reaction conditions, low yields, or the formation of side products. Hence, direct transformation of readily available aromatic ketones into valuable 2-hydroxylated products by transition metal-catalyzed C-H functionalization is arguably a highly efficient and atom-economic method to access these compounds. Moreover, developing a more general strategy for the regio- and chemoselective C-H oxygenation of a variety of challenging arenes would be especially desirable for phenol synthesis (Scheme 1).
- Shan, Gang,Yang, Xinglin,Ma, Linlin,Rao, Yu
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supporting information
p. 13070 - 13074
(2013/02/26)
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- Low-energy collision-induced fragmentation of negative ions derived from ortho-, meta-, and para-hydroxyphenyl carbaldehydes, ketones, and related compounds
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Collision-induced dissociation (CID) mass spectra of anions derived from several hydroxyphenyl carbaldehydes and ketones were recorded and mechanistically rationalized. For example, the spectrum of m/z 121 ion of deprotonated ortho-hydroxybenzaldehyde shows an intense peak at m/z 93 for a loss of carbon monoxide attributable to an ortho-effect mediated by a charge-directed heterolytic fragmentation mechanism. In contrast, the m/z 121 ion derived from meta and para isomers undergoes a charge-remote homolytic cleavage to eliminate an ?H and form a distonic anion radical, which eventually loses CO to produce a peak at m/z 92. In fact, for the para isomer, this two-step homolytic mechanism is the most dominant fragmentation pathway. The spectrum of the meta isomer on the other hand, shows two predominant peaks at m/z 92 and 93 representing both homolytic and heterolytic fragmentations, respectively. 18O-isotope-labeling studies confirmed that the oxygen in the CO molecule that is eliminated from the anion of meta-hydroxybenzaldehyde originates from either the aldehydic or the phenolic group. In contrast, anions of ortho-hydroxybenzaldehyde and 2-hydroxy-1-naphthaldehyde, both of which show two consecutive CO eliminations, specifically lose the carbonyl oxygen first, followed by that of the phenolic group. Anions from 2-hydroxyphenyl alkyl ketones lose a ketene by a hydrogen transfer predominantly from the α position. Interestingly, a very significant charge-remote 1,4-elimination of a H2 molecule was observed from the anion derived from 2,4-dihydroxybenzaldehyde. For this mechanism to operate, a labile hydrogen atom should be available on the hydroxyl group adjacent to the carbaldehyde functionality. Copyright
- Attygalle, Athula B.,Ruzicka, Josef,Varughese, Deepu,Bialecki, Jason B.,Jafri, Sayed
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p. 1207 - 1217
(2008/03/11)
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- Oppenauer-type oxidation of secondary alcohols catalyzed by homogeneous water-soluble complexes
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The catalytic system composed of [Ir(COD)Cl]2, 2,2′-biquinoline-4,4′-dicarboxylic acid dipotassium salt (BQC), and sodium carbonate is highly efficient for the selective oxidation of benzylic, 1-heteroaromatic, aliphatic, and allylic secondary alcohols using catalyst:substrate ratios ranging from 0.4% to 2.5%. Sterically hindered allylic alcohols undergo selectively good conversions to the corresponding enones, while unhindered ones are completely isomerized to saturated ketones. Mercury tests indicate that the catalytic process is likely homogeneous. The mechanism proposed for this Oppenauer-type oxidation including the isomerization process is based on iridium-alkoxide species.
- Ajjou, Abdelaziz Nait,Pinet, Jean-Louis
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p. 702 - 710
(2007/10/03)
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- Non-metallocene compounds, method for the production thereof and use of the same for the polymerisation of olefins
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The invention relates to a method for producing special transition metal compounds, to novel transition metal compounds and to the use of the same for the polymerisation of olefins.
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- Fries rearrangement at atmospheric pressure using microwave irradiation
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A very safe, fast and practical Fries rearrangement with conventional AlCl3 catalyst, carried out in a modified domestic microwave oven at atmospheric pressure is reported.
- Khadilkar, Bhushan M.,Madyar, Virendra R.
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p. 1195 - 1200
(2007/10/03)
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- 4-derivatives coumarin-3-phosphonic acids and esters
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In the Arbuzov reactions of 2′-bromoacetoxyphenone with trimethyl phosphite the derivatives in position 4 of 3-phosphonocoumarinic acids and esters were obtained.
- Kostka, Krzysztof,Pastuszko, Slawomir,Kotynski, Andrzej,Budzisz, Elzbieta
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p. 199 - 209
(2007/10/03)
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- Alkylation of dianions derived from 2-(1-iminoalkyl) phenols: Synthesis of functionalized 2-acyl phenols
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A method has been developed for the almost exclusive C-alkylation of the 2-(l-liminoalkyl) phenols 1, important organic compounds with a range of employment, which allows the preparation of complex derivatives 4 with good yields starting from easily available materials. The operational simplicity of this method take advantages in providing a variety of alkylated 2-acyl phenols 5 by an easy hydrolysis of the 2-(1-iminoalkyl) phenols 4.
- Cimarelli, Cristina,Palmieri, Gianni
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p. 15711 - 15720
(2007/10/03)
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- Calcium metal in liquid ammonia for selective reduction of organic compounds
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Selective reduction of functional groups by use of dissolving calcium metal was performed, and the results are in comparison with those by lithium and sodium metals. Reduction with 2.0-2.2 equiv of calcium led chromone (1) to 4-chromanone (2, 75% yield), coumarin (4) to dihydrocoumarin (5, 76% yield) and 3-(2-hydroxyphenyl)-1-propanol (6, 6% yield), α-tetralone (7) to 1,2,3,4-tetrahydro-1-naphthol (8, 81% yield), and β-methoxystyrene (12) to methyl phenethyl ether (13, 85% yield). Performance of reductions on the same substrates by use of 4.0 equiv of lithium or sodium metal gave over-reduced products. Reduction of indole-3-carboxaldehyde (15) to 3-indolemethanol (16), 1-acetylnaphthalene (17) to 1-acetyl-3,4-dihydronaphthalene (18), and trans-4-phenyl-3-buten-2-one (19) to 4-phenyl-2-butanone (20) were accomplished by use of calcium, lithium, and sodium metals, among which calcium gave the highest yields (80-90%). Being a milder reducing agent than lithium and sodium, calcium metal in liquid ammonia offered a better selectivity.
- Hwu, Jih Ru,Wein,Leu, Yi-Jing
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p. 1493 - 1498
(2007/10/03)
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- PRODRUGS OF IMIDAZOLE CARBOXYLIC ACIDS AS ANGIOTENSIN II RECEPTOR ANTAGONISTS
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Prodrugs of imidazole carboxylic acids which are AII antagonists useful in treating hypertension, pharmaceutical compositions thereof and a method of treating hypertension using such prodrugs are disclosed.
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- β-Cyclodextrin Effects on the Photo-Fries Rearrangement of Aromatic Alkyl Esters
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The photolysis of phenyl propionate (1a) and phenyl valerate (1b) in water and in solutions containing β-cyclodextrin (CD) leads to the corresponding p-hydroxyphenyl alkyl ketone 2, o-hydroxyphenyl alkyl ketone 3, and phenol 4.When the reactions are carried out in the presence of oxygen there is a decrease in the total amount of rearrangement products, but the inhibition is less marked in the presence of CD.The / ratio for 1b increases when CD concentration changes from 0 to 10 mM.These changes are due to the increase in the quantum yield for the formation of 3 and a decrease in the quantum yield for 2 in the solutions containing CD.The / ratio for 1a decreases in the presence of CD although both quantum yields increase with CD concentrations.Under the conditions used in this study, the substrate reacted in the bulk solution and in the cavity of CD.The quantum yields for the formation of 3 and 4, ΦCD3 and ΦCD4, are higher for the included substrate than the corresponding values for the free substrate while ΦCD2 is higher than Φw2 for 1a but lower for 1b.This effect is attributed to the different orientation of the substrates in the cavity of CD.Besides, ΦCD4 also increases due to the availability of hydrogens bonded to secondary carbons in the cavity of the cyclodextrin.
- Veglia, Alicia V.,Rossi, Rita H. de
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p. 4941 - 4944
(2007/10/02)
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- BETA-ADRENERGIC BLOCKING AGENTS IN THE 1,2,3-THIADIAZOLE SERIES
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Novel 4-2,3 or 4(3-amino-2-hydroxypropoxy) phenyl!-and 5-2, 3 or 4(3-amino-2-hydroxypropoxy) phenyl!-1,2,3-thiadiazole derivatives which may be further substituted at the C-5 or C-4 position of the thiadiazole ring, respectively, by a lower alkyl, phenyl, trifluoromethyl, carboxy, alkoxycarbonyl, cyano or an aminocarbonyl group, and the pharmaceutically acceptable acid addition salts thereof and processes for the production of such compounds; 4-4(3-t-butylamino-2-hydroxypropoxy) phenyl!-1,2,3-thiadiazole and 5-4(3-t-butylamino-2-hydroxypropoxy) phenyl!-1,2,3-thiadiazole are representative of the class. These compounds possess cardiovascular activity and are useful for the treatment of abnormal heart conditions in mammals.
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