- ADDITIONS OF SUBSTITUTED PHENYLTHIYL RADICALS TO SUBSTITUTED α-METHYLSTYRENES. GROUND STATE AND TRANSITION STATE ELECTRONIC EFFECTS
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The radical addition of substituted thiophenols to α-methylstyrene and substituted α-methylstyrenes has been investigated at 70 deg C.Relative reactivities of pairs of thiophenols competing with individual alkenes can be utilized to obtain Hammett correlations.The interplay of substituent effects in alkene and thiyl radical leads to examples of non-linear rho values.Rationales for this behavior will be offered in terms of variable contributions from ground state and transition state electronic factors as well as in terms of possible mechanistic changes.
- Geers, Brian N.,Gleicher, Gerald Jay,Church, Daniel F.
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- Bifunctional catalyst Pd-Al-MCM-41 for efficient dimerization-hydrogenation of β-pinene in one pot
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A new type of bimetallic palladium and aluminum incorporated mobile crystalline materials (Pd-Al-MCM-41) as bifunctional catalysts has been hydrothermally synthesized. Characterization shows that these molecular materials exhibit an ordered mesoporous structure, high surface area and a good dispersion of palladium in the frame. The catalytic activity of the Pd-Al-MCM-41 for the dimerization-hydrogenation reaction system of β-pinene in one pot has been systematically studied. Pd0.5-Al30-MCM-41 (SiO2/Al2O3 = 30, 0.5 wt% palladium content) was found to be the best catalyst which gave a dimer yield of up to 64.7%. It is worth noting that palladium shows a good synergic catalytic effect with aluminum in the dimerization reaction and enhances the dimerization yield. Furthermore, the bifunctional catalyst displayed a good activity over 4 runs.
- Zhang, Song,Xu, Chao,Zhai, Guoqing,Zhao, Mingliang,Xian, Mo,Jia, Yuxiang,Yu, Zongjiang,Liu, Fusheng,Jian, Fangfang,Sun, Weizhi
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- Synthesis of N-Alkylpyridin-4-ones and Thiazolo[3,2- a]pyridin-5-ones through Pummerer-Type Reactions
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N-Alkylated 4-pyridones were obtained through a one-pot procedure involving either normal or interrupted Pummerer reactions between triflic anhydride-activated sulfoxides and 4-fluoropyridine derivatives, followed by hydrolysis. On the other hand, triflic anhydride-activated benzyl 6-fluoro-2-pyridyl sulfoxide could react with alkenes or alkynes to afford thiazolo[3,2-a]pyridin-5-ones, via the pyridinium salt intermediates.
- Huang, Jingjia,Hu, Gang,An, Shaoyu,Chen, Dongding,Li, Minglei,Li, Pingfan
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- Effect of iron content on selectivity in isomerization of α-pinene oxide to campholenic aldehyde over Fe-MMM-2 and Fe-VSB-5
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Isomerization of α-pinene oxide to campholenic aldehyde (CA) was investigated over Fe-containing mesoporous mesophase materials (Fe-MMM-2) and microporous nickel phosphate molecular sieves (Fe-VSB-5). Activity and selectivity of reaction towards CA over Fe-containing materials was found to depend on iron content in materials that affects oligomeric state of Fe and amount of Lewis acid sites. In the presence of Fe-VSB-5 selectivity towards CA increased with increase in iron content in structure, while that decreased in the presence of Fe-MMM-2. This phenomenon is related to change in agglomeration of iron species in Fe-MMM-2 structure. The high selectivity towards CA in the presence of Fe-VSB-5 was suggested to arise from unique structure of these materials, which favours shape selectivity.
- Timofeeva,Panchenko,Hasan, Zubair,Khan, Nazmul Abedin,Mel'Gunov,Abel,Matrosova,Volcho,Jhung, Sung Hwa
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- Cu/Ni-Catalyzed Cyanomethylation of Alkenes with Acetonitrile for the Synthesis of β,γ-Unsaturated Nitriles
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We have developed a protocol for the Cu/Ni-catalyzed cyanomethylation of alkenes with acetonitrile for the synthesis of β,γ-unsaturated nitriles. This is the first example of a direct coupling of the alkene sp2 C - H bond and the acetonitrile sp3 C - H bond for the preparation of β,γ-unsaturated nitriles. Acetonitrile, an inexpensive and stable solvent, is demonstrated to be a useful cyanomethyl source. The combination of copper and nickel catalysts resulted in a high reaction efficiency.
- Jian, Hong,Shen, Zengming,Zhang, Saisai
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- Thermal and Photochemical Nitration of Aromatic Hydrocarbons with Nitrogen Dioxide
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Aromatic hydrocarbons (ArH) are readily nitrated by nitrogen dioxide (NO2) in dichloromethane at room temperature and below (in the dark).The red colors, transiently observed, arise from the metastable precursor complex NO3(1-), which is formed in the prior disproportionation of nitrogen dioxide induced by the aromatic donor (eq 7).The deliberate irradiation of the diagnostic (red) charge-transfer absorption band (hνCT) of NO3(1-) at low temperatures results directly in aromatic nitration, even at -78 deg C, where the thermal nitration is too slow to complete.The mechanism of the photochemical (charge-transfer) nitration is established by time-resolved laser spectroscopy to proceed via the aromatic cation radical (ArH.+) formed spontaneously upon the charge-transfer excitation of NO3(1-) in Scheme 1.The related thermal activation of NO3(1-) derives from the adiabatic electron transfer that produces the same radical pair as the reactive intermediate in Scheme 3.The close relationship between the thermal/photochemical nitrations with nitrogen dioxide and those conventionally carried out with nitric acid (in the presence of nitrous acid) is delineated by Scheme 4.
- Bosch, E.,Kochi, J. K.
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- The selective conversion of D-limonene to p,α-dimethylstyrene
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Reaction conditions to facilitate the conversion of D-limonene selectively to p,α-dimethylstyrene (DMS) are described, in order to subsequently produce polymeric materials from biomass sourced from food waste. Limonene was dehydrogenated with several palladium catalysts and different solvents and bases, with copper chloride as oxidant at temperatures of 70-120 °C. Reaction conditions were identified using Pd(OAc)2 for the selective formation of only DMS from limonene in 2-5 hours, enabling the facile separation of DMS from unreacted starting material by vacuum distillation.
- Sanchez-Vazquez,Sheppard,Evans,Hailes
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- Desaturation of alkylbenzenes by cytochrome P450BM3 (CYP102A1)
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A study was conducted to investigate the desaturation of alkylbenezenes by cytochrome P450BM3 (CYP102A1). It was observed during the study that oxidation of alkylbenzenes with CYP102A1 involves a gamut of P450 activity types that are terminal, sub-terminal benzylic and aromatic hydroxylation; terminal and sub-terminal desaturation; and epoxidation of the olefins. It was also found that the desaturation of cumene by CYP102A1 is sensitive to α-deuteration and insensitive to β-deuteration. Intramolecular deuterium isotope study revealed that the first abstraction in the desaturation of valproic acid and ezlopitant by microsomal P450s take place from activated carbon atoms. The increased β-hydroxylation percentages show that the β-carbon lies closer to the ferryl oxygen in the KT5.
- Whitehouse, Christopher J.C.,Bell, Stephen G.,Wong, Luet-Lok
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- The Convenient Way for Obtaining Geranial by Acid-Catalyzed Kinetic Resolution of Citral
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A new simple method has been developed for isolation of geranial from citral, which is a mixture of two isomeric aldehydes, geranial and neral. The storage of citral in the presence of K10 montmorillonite clay has been demonstrated to result in an almost complete conversion of neral to dimeric and oligomeric products, with most geranial remaining unconverted. This enables isolation of geranial with the yield of up to 94%, based on the amount of geranial originally present in citral.
- Il'Ina, Irina V.,Volcho, Konstantin P.,Korchagina, Dina V.,Salakhutdinov, Nariman F.
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- Investigations into the mechanism of action of nitrobenzene as a mild dehydrogenating agent under acid-catalysed conditions
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Protonated nitrobenzene can be used to dehydrogenate a range of hydrocarbons, which already possess at least one double bond. Kinetic and spectroscopic results, together with known electrode potentials, yield approximate limits within which protonated nitrobenzenes can be expected to effect dehydrogenation of hydroaromatic compounds. A high yielding synthesis of benzo[j]fluoranthene is described.
- Cristiano, M. Lurdes S.,Gago, David J.P.,Gonsalves, Antonio M. A. Rocha,Johnstone, Robert A.W.,McCarron, Moya,Varejao, Jorge M.T.B.
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- Photoinduced Hydroarylation and Cyclization of Alkenes with Luminescent Platinum(II) Complexes
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Photoinduced hydroarylation of alkenes is an appealing synthetic strategy for arene functionalization. Herein, we demonstrated that aryl radicals generated from electron-deficient aryl chlorides/bromides could be trapped by an array of terminal/internal aryl alkenes in the presence of [Pt(O^N^C^N)] under visible-light (410 nm) irradiation, affording anti-Markovnikov hydroarylated compounds in up to 95 % yield. Besides, a protocol for [Pt(O^N^C^N)]-catalyzed intramolecular photocyclization of acrylanilides to give structurally diverse 3,4-dihydroquinolinones has been developed.
- Cheng, Hanchao,Lam, Tsz-Lung,Liu, Yungen,Tang, Zhou,Che, Chi-Ming
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p. 1383 - 1389
(2020/11/30)
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- 1,3-Difunctionalization of β-alkyl nitroalkenes via combination of Lewis base catalysis and radical oxidation
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Upon treatment with a Lewis base catalyst, β-alkyl-substituted nitroalkenes could be readily converted into allylic nitro compounds. Examples of either C-1 or C-3 functionalization methods have been reported through nitro-elimination, giving alkene products. In this work, successful 1,3-difunctionalization was achieved through a synergetic Lewis base catalysis and TBHP radical oxidation, giving vinylic alkoxyamines in good to excellent yields. This work further extended the general synthetic application of β-alkyl nitroalkenes.
- Wang, Ye,Zheng, Lei,Shi, Xiaodong,Chen, Yunfeng
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supporting information
p. 886 - 889
(2021/02/01)
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- Visible-Light-Induced Meerwein Fluoroarylation of Styrenes
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An unprecedented approach for assembling a broad range of 1,2-diarylethane derivatives with fluorine-containing fully substituted carbon centers was developed. The protocol features straightforward operation, proceeds under metal-free condition, and accommodates a large variety of synthetically useful functionalities. The critical aspect to the success of this novel transformation lies in using aryldiazonium salts as both aryl radical progenitor and also as single electron acceptor which elegantly enables a radical-polar crossover manifold.
- Tang, Hai-Jun,Zhang, Bin,Xue, Fei,Feng, Chao
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supporting information
p. 4040 - 4044
(2021/05/26)
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- Enantioselective Hydrothiolation: Diverging Cyclopropenes through Ligand Control
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In this article, we advance Rh-catalyzed hydrothiolation through the divergent reactivity of cyclopropenes. Cyclopropenes undergo hydrothiolation to provide cyclopropyl sulfides or allylic sulfides. The choice of bisphosphine ligand dictates whether the pathway involves ring-retention or ring-opening. Mechanistic studies reveal the origin for this switchable selectivity. Our results suggest the two pathways share a common cyclopropyl-Rh(III) intermediate. Electron-rich Josiphos ligands promote direct reductive elimination from this intermediate to afford cyclopropyl sulfides in high enantio- A nd diastereoselectivities. Alternatively, atropisomeric ligands (such as DTBM-BINAP) enable ring-opening from the cyclopropyl-Rh(III) intermediate to generate allylic sulfides with high enantio- A nd regiocontrol.
- Dong, Vy M.,Kuker, Erin L.,Lu, Alexander,Nie, Shaozhen
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supporting information
p. 6176 - 6184
(2021/05/07)
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- Palladium-Catalyzed Markovnikov Hydroaminocarbonylation of 1,1-Disubstituted and 1,1,2-Trisubstituted Alkenes for Formation of Amides with Quaternary Carbon
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Hydroaminocarbonylation of alkenes is one of the most promising yet challenging methods for the synthesis of amides. Herein, we reported the development of a novel and effective Pd-catalyzed Markovnikov hydroaminocarbonylation of 1,1-disubstituted or 1,1,2-trisubstituted alkenes with aniline hydrochloride salts to afford amides bearing an α quaternary carbon. The reaction makes use of readily available starting materials, tolerates a wide range of functional groups, and provides a facile and straightforward approach to a diverse array of amides bearing an α quaternary carbon. Mechanistic investigations suggested that the reaction proceeded through a palladium hydride pathway. The hydropalladation and CO insertion are reversible, and the aminolysis is probably the rate-limiting step.
- Yang, Hui-Yi,Yao, Ya-Hong,Chen, Ming,Ren, Zhi-Hui,Guan, Zheng-Hui
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supporting information
p. 7298 - 7305
(2021/05/26)
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- Ni-Catalyzed Reductive Allylation of α-Chloroboronates to Access Homoallylic Boronates
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The transition-metal-catalyzed allylation reaction is an efficient strategy for the construction of new carbon-carbon bonds alongside allyl or homoallylic functionalization. Herein we describe a Ni-catalyzed reductive allylation of α-chloroboronates to efficiently render the corresponding homoallylic boronates, which could be readily converted into valuable homoallylic alcohols or amines or 1,4-diboronates. This reaction features a broad substrate scope with good functional group compatibility that is complementary to the existing methods for the preparation of homoallylic boronates.
- Lou, Yixian,Qiu, Jian,Yang, Kai,Zhang, Feng,Wang, Chenglan,Song, Qiuling
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supporting information
p. 4564 - 4569
(2021/06/28)
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- MnBr2 catalyzed regiospecific oxidative Mizoroki-Heck type reaction
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Herein, we report an unprecedented regiospecific oxidative Mizoroki-Heck type reaction for the synthesis of ɑ-difluoromethyl homoallylic alcohols. The reaction shows broad substrate scopes and high functional group tolerance. Late-stage functionalization of complex biologically active molecules demonstrates the synthetic potential of this transformation. Mechanistic study supports the involvement of MnBr2 catalyzed radical 1,2-silyl transfer.
- Chen, Xiang,Chen, Yi-Hung,Liu, Shanshan,Shen, Xiao,Zhu, Zhihong
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supporting information
(2021/11/27)
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- Mesoporous tin phosphate as an effective catalyst for fast cyclodehydration of bio-based citral into p-cymene
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Effective synthesis of aromatic compounds from renewable biomass is highly important yet challenging. p-Cymene is an attractive aromatic compound with various promising applications in the manufacture of fine chemicals. In this study, a novel and effective catalytic system based on mesoporous tin phosphate (M-SnPO) with Lewis-Br?nsted dual acidity was developed for the fast synthesis of p-cymene from the cyclodehydration of bio-based citral. Up to 78.5% yield of p-cymene was achieved from the cyclodehydration of citral at 180 °C within only 0.5 h, superior to the results reported for benchmark homogeneous acid catalysts. Characterization of as-prepared M-SnPO catalyst via various techniques indicates that the synergic effect of Lewis and Br?nsted acidic sites, large pore-sized structure, and high surface area are responsible for its remarkable catalytic performance. In addition, the effectiveness of the M-SnPO catalyst could be almost sustained over multiple cycles without significant loss. The work herein is the first example of developing a Lewis-Br?nsted dual acidic heterogeneous catalyst for the fast synthesis of p-cymene from the cyclodehydration of citral.
- He, Jian,Li, Hu,Wu, Hongguo,Yang, Song,Yu, Zhaozhuo
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- Experimental and Computational Studies of Palladium-Catalyzed Spirocyclization via a Narasaka-Heck/C(sp3or sp2)-H Activation Cascade Reaction
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The first synthesis of highly strained spirocyclobutane-pyrrolines via a palladium-catalyzed tandem Narasaka-Heck/C(sp3 or sp2)-H activation reaction is reported here. The key step in this transformation is the activation of a δ-C-H bond via an in situ generated σ-alkyl-Pd(II) species to form a five-membered spiro-palladacycle intermediate. The concerted metalation-deprotonation (CMD) process, rate-determining step, and energy barrier of the entire reaction were explored by density functional theory (DFT) calculations. Moreover, a series of control experiments was conducted to probe the rate-determining step and reversibility of the C(sp3)-H activation step.
- Wei, Wan-Xu,Li, Yuke,Wen, Ya-Ting,Li, Ming,Li, Xue-Song,Wang, Cui-Tian,Liu, Hong-Chao,Xia, Yu,Zhang, Bo-Sheng,Jiao, Rui-Qiang,Liang, Yong-Min
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supporting information
p. 7868 - 7875
(2021/05/27)
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- 3 -trifluoromethyl -5 - aryl -1, 6 -dihydropyridazine compound and preparation method thereof (by machine translation)
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The invention relates to 3 - trifluoromethyl -5 - aryl -1, 6 -dihydropyridazine compound, and the structural formula of the compound is as follows. Ar refers to Ar. . . One of the following. , The invention also discloses a preparation method of the compound. To the invention, the oxidation/cyclization reaction of 4 - aryl substituted trifluoromethylhomoallylhydrazine is promoted by copper acetate, 3 - trifluoromethyl -5 - aryl -1 and 6 -dihydropyridazine compound with obvious aggregation-induced emission effect are obtained. (by machine translation)
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Paragraph 0036-0037; 0042-0043
(2020/08/25)
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- Additions of Aldehyde-Derived Radicals and Nucleophilic N-Alkylindoles to Styrenes by Photoredox Catalysis
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The consecutive addition of acyl radicals and N-alkylindole nucleophiles to styrenes was established, as well as some additional radical-nucleophile combinations. Both aryl and aliphatic aldehydes give reasonable yields. The reaction proceeds best for α-substituted styrenes, effectively creating a quaternary all-carbon center. Some iridium-based photoredox systems are catalytically active; furthermore, a base is needed in this transformation. Radicals are formed by reductive perester cleavage and hydrogen atom transfer.
- Klussmann, Martin,Lux, Marcel
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supporting information
(2020/04/30)
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- Aqueous ZnCl2 Complex Catalyzed Prins Reaction of Silyl Glyoxylates: Access to Functionalized Tertiary α-Silyl Alcohols
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An efficient Prins reaction of silyl glyoxylates in the presence of an aqueous ZnCl2 complex as a catalyst was developed, providing functionalized tertiary α-silyl alcohols in high yields under mild conditions. A preliminary investigation indicated that the aqueous ZnCl2 complex acted as a dual functional catalyst of Br?nsted and Lewis acid to activate the carbonyl groups of silyl glyoxylates via a dual-activation model.
- Han, Man-Yi,Pan, Hong,Li, Pinhua,Wang, Lei
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p. 5825 - 5837
(2020/05/22)
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- Synthesis of Tertiary Benzylic Nitriles via Nickel-Catalyzed Markovnikov Hydrocyanation of α-Substituted Styrenes
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The Markovnikov hydrocyanation of α-substituted styrenes enables the synthesis of tertiary benzylic nitriles under nickel catalysis. The Lewis-acid-free transformation features an unprecedented functional groups tolerance, including the-OH and-NH2 groups. A broad range of tertiary benzylic nitriles were obtained in good to excellent yields. In addition, an asymmetric version of this reaction was preliminarily investigated.
- Xing, Yidan,Yu, Rongrong,Fang, Xianjie
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supporting information
p. 1008 - 1012
(2020/02/04)
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- Palladium/Acid Relay Catalyzed Tandem Heck Coupling/6-Endo Cyclization between ortho-Halogenated Benzoates and Unactivated Terminal Alkenes for the Synthesis of 1-Isochromanones
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We report a unique and expeditious route to synthesize 1-isochromanone derivatives through palladium catalyzed tandem Heck coupling/6-endo hydroacyloxylation cyclization between readily available ortho-halogenated benzoates and unactivated alkenes. Various 2-bromo or 2-iodo benzoates can be coupled efficiently with a broad range of alkenes to afford functionalized 1-isochromanones in high yields. Significantly, this cost-efficient and easy-to-handle synthetic methodology will have great prospect application in the synthetic and medicinal chemistry. (Figure presented.).
- Wen, Zhen-Kang,Ge, Xiao-Min,Zhao, Ze-Kai,Chao, Jian-Bin
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supporting information
p. 983 - 988
(2019/01/30)
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- A convenient access to allylic triflones with allenes and triflyl chloride in the presence of (EtO)2P(O)H
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A simple method for the preparation of allylic triflones from allenes and triflyl chloride in the presence of (EtO)2P(O)H has been developed. The features of this reaction are catalyst-free and simple starting substrates. This method tolerates diverse functional groups and substituted allylic triflones are obtained in moderate to good yields.
- Ni, Jixiang,Jiang, Yong,An, Zhenyu,Lan, Jingfeng,Yan, Rulong
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supporting information
p. 7343 - 7345
(2019/06/27)
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- Highly Enantioselective Iridium-Catalyzed Hydrogenation of 2-Aryl Allyl Phthalimides
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The iridium-catalyzed asymmetric hydrogenation of 2-aryl allyl phthalimides to afford enantioenriched β-aryl-β-methyl amines is presented. Recently developed Ir-MaxPHOX catalysts are used for this enantioselective transformation. The mild reaction conditions and the feasible removal of the phthalimido group makes this catalytic method easily scalable and of great interest to afford chiral amines. The importance of this new methodology is exemplified by the formal synthesis of (R)-Lorcaserin, OTS514, and enantiomerically enriched 3-methyl indolines.
- Cabré, Albert,Romagnoli, Elia,Martínez-Balart, Pol,Verdaguer, Xavier,Riera, Antoni
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supporting information
p. 9709 - 9713
(2019/11/19)
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- Copper-Catalyzed Enantio- and Diastereoselective Addition of Silicon Nucleophiles to 3,3-Disubstituted Cyclopropenes
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A highly stereocontrolled syn-addition of silicon nucleophiles across cyclopropenes with two different geminal substituents at C3 is reported. Diastereomeric ratios are excellent throughout (d.r.≥98:2) and enantiomeric excesses usually higher than 90 %, even reaching 99 %. This copper-catalyzed C?Si bond formation closes the gap of the direct synthesis of α-chiral cyclopropylsilanes.
- Zhang, Liangliang,Oestreich, Martin
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supporting information
p. 14304 - 14307
(2019/11/13)
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- Regioselective Diboron-Mediated Semireduction of Terminal Allenes
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A method for the regioselective reduction of the terminal double bond of 1,1-disubstituted allenes has been developed. In the presence of a palladium catalyst, tetrahydroxydiboron and stoichiometric water, allene semireduction proceeds in high yield to afford Z-alkenes selectively.
- Gates, Ashley M.,Santos, Webster L.
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supporting information
p. 4619 - 4624
(2019/12/11)
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- Catalyst-Free Enantiospecific Olefination with In Situ Generated Organocerium Species
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Described is the in situ formation of triorganocerium reagents and their application in catalyst-free Zweifel olefinations. These unique cerium species were generated through novel exchange reactions of organohalides with n-Bu3Ce reagents. The adequate electronegativity of cerium allowed for compensating the disadvantages of both usually functional-group-sensitive organolithium species and less reactive organomagnesium reagents. Exchange reactions were performed on aryl and alkenyl bromides, enabling enantiospecific transformations of chiral boron pinacol esters. Finally, these new organocerium species were engaged in selective 1,2-additions onto enolisable and sterically hindered ketones.
- Music, Arif,Hoarau, Clément,Hilgert, Nicolas,Zischka, Florian,Didier, Dorian
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supporting information
p. 1188 - 1192
(2019/01/04)
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- Iridium-Catalyzed Isomerization of N-Sulfonyl Aziridines to Allyl Amines
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The Crabtree's reagent catalyzes the isomerization of N-sulfonyl 2,2-disubstituted aziridines to allyl amines. The selectivity of allyl amine vs imine is very high (up to 99/1). The unprecedented isomerization takes place in mild conditions without activation of the catalyst by hydrogen. The mechanism has been studied computationally by DFT calculations; instead of the usual hydrogenation of COD, the catalytic species is formed by a loss of the pyridine ligand. Approaching of aziridine to this unsaturated species leads to a carbocation intermediate through a low energy barrier. A metal-mediated tautomerization involving sequentially γ-H elimination and N-H reductive elimination affords selectively the allyl amine. The readiness of the CγH bond to participate in the H elimination step accounts for the selectivity toward the allyl amine product.
- Cabré, Albert,Sciortino, Giuseppe,Ujaque, Gregori,Verdaguer, Xavier,Lledós, Agustí,Riera, Antoni
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supporting information
p. 5747 - 5751
(2018/09/21)
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- Regioselective Copper-Catalyzed Oxidative Coupling of α-Alkylated Styrenes with Tertiary Alkyl Radicals
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A radical-mediated oxidative cross-coupling of readily accessible α-alkylated styrenes with 1,3-dicarbonyl compounds utilizing a combination of Cu(OAc)2 and air as a catalytic system is described. Rather than requiring α-halocarbonyl compounds, this efficient approach enables direct installation of tertiary functionalized alkyl motifs to olefins with simple carbonyl derivatives. The novel protocol is characterized with high allylic selectivities via a competing β-H elimination. Both radical-clock and -trapping experiments provided clear-cut evidence for the intermediacy of an α-keto carbon-centered radical.
- Wang, Cong,Liu, Rui-Hua,Tian, Ming-Qing,Hu, Xu-Hong,Loh, Teck-Peng
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supporting information
p. 4032 - 4035
(2018/07/15)
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- Rhodium-Catalyzed Enantioconvergent Isomerization of Homoallylic and Bishomoallylic Secondary Alcohols
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We present herein an unprecedented enantioselective isomerization of homoallylic and bishomoallylic secondary alcohols, catalyzed by a commercially available rhodium-complex and a base. This catalytic redox-neutral process provides an effective access to chiral ketones in high efficiency and enantioselectivity, without the use of any stoichiometric reagent or generation of any waste. For the reaction of homoallylic alcohols, this system achieved not only a stereoconvergent access to chiral ketones bearing a β-stereocenter (up to 95%, 86% ee) but also a concomitant oxidative kinetic resolution of the alcohol substrates (S > 20). In the case of bishomoallylic alcohols, an intriguing ligand-induced divergent reactivity was observed. A terminal-to-internal alkene isomerization promoted by Rh/L7 followed by redox isomerization using Rh/BINAP system produced chiral ketones bearing a γ-stereocenter with high yield and enantioselectivity. Mechanistic studies provided strong support for the redox-isomerization pathway with chain walking of the key alkyl-Rh intermediate.
- Huang, Rui-Zhi,Lau, Kai Kiat,Li, Zhaofeng,Liu, Tang-Lin,Zhao, Yu
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supporting information
p. 14647 - 14654
(2018/11/06)
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- Catalytic Hydrodefluorination of C?F Bonds by an Air-Stable PIII Lewis Acid
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Catalytic hydrodefluorination (HDF) of unactivated fluoroalkanes or CF3-substituted aryl species is performed using the PIII Lewis acids, [(bipy)PPh]2+ (12+) and [(terpy)PPh]2+ (22+) under
- Chitnis, Saurabh S.,Krischer, Felix,Stephan, Douglas W.
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p. 6543 - 6546
(2018/04/26)
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- Asymmetric carbonyl-ene reaction of trifluoropyruvate catalyzed by Pd(II)-SunPhos complex
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An efficient asymmetric carbonyl-ene reaction of trifluoropyruvate catalyzed by chiral Pd(II)/(S)-SunPhos complex was developed. A series of optically active homoallylic alcohols containing a CF3 group were obtained with high yields and excellent ee under mild conditions. Particularly, the reaction of isobutylene and trifluoropyruvate gave the desired product (90% yield, 98% ee) with catalyst loading as low as 0.01 mol% in dichloroethane/toluene.
- Jiang, Lili,Hu, Bei,Xie, Xiaomin,Zhang, Zhaoguo
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supporting information
p. 6901 - 6905
(2017/10/31)
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- Palladium-Catalyzed Direct Intramolecular C-N Bond Formation: Access to Multisubstituted Dihydropyrroles
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A palladium-catalyzed intramolecular amination of alkenes with retention of olefin functionalization was achieved under mild reaction conditions. In the presence of palladium catalyst, the tosyl-protected amine can directly couple with a double bond to provide versatile dihydropyrrole derivatives in moderate to excellent yields.
- Jiang, Bing,Meng, Fei-Fan,Liang, Qiu-Ju,Xu, Yun-He,Loh, Teck-Peng
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supporting information
p. 914 - 917
(2017/02/26)
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- Water-Enabled Catalytic Asymmetric Michael Reactions of Unreactive Nitroalkenes: One-Pot Synthesis of Chiral GABA-Analogs with All-Carbon Quaternary Stereogenic Centers
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Water enables new catalytic reactions for otherwise unreactive substrate systems. Under the “on water” reaction conditions, extremely unreactive β,β-disubstituted nitroalkenes smoothly underwent enantioselective Michael addition reactions with dithiomalonates using a chiral squaramide catalyst, affording both enantiomers of highly enantioenriched Michael adducts with all-carbon-substituted quaternary centers. The developed “on water” protocol was successfully applied for the scalable one-pot syntheses of chiral GABA analogs with all-carbon quaternary stereogenic centers at the β-position, which might show highly interesting pharmaceutical properties.
- Sim, Jae Hun,Song, Choong Eui
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supporting information
p. 1835 - 1839
(2017/02/05)
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- Chelation versus Non-Chelation Control in the Stereoselective Alkenyl sp2 C?H Bond Functionalization Reaction
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A hydroxy group chelation-assisted stereospecific oxidative cross-coupling reaction between alkenes was developed under mild reaction conditions. In the presence of palladium catalyst, the alkenes tethered with hydroxy functionality can couple efficiently with electron-deficient alkenes to form the corresponding multi-substituted olefin products. The hydroxy group on the substrate could play dual roles in reaction, acting as the directing group for alkenyl C?H bond activation and controlling the stereoselectivity of the products.
- Liang, Qiu-Ju,Yang, Chao,Meng, Fei-Fan,Jiang, Bing,Xu, Yun-He,Loh, Teck-Peng
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supporting information
p. 5091 - 5095
(2017/04/24)
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- Visible-Light Photocatalytic Bicyclization of 1,7-Enynes toward Functionalized Sulfone-Containing Benzo[a]fluoren-5-ones
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A new visible-light photocatalytic arylsulfonylation and bicyclization of C(sp3)-tethered 1,7-enynes with sulfinic acids has been developed, delivering functionalized sulfone-containing benzo[a]fluoren-5-ones with generally good yields. This Eosin Y-catalyzed approach makes use of visible light as a safe and eco-friendly energy source to drive cascade cyclization reactions, resulting in continuous multiple bond-forming events including C–S and C–C bonds to efficiently construct polycyclic-linked alkyl aryl sulfones. (Figure presented.).
- Huang, Min-Hua,Zhu, Yi-Long,Hao, Wen-Juan,Wang, Ai-Fang,Wang, De-Cai,Liu, Feng,Wei, Ping,Tu, Shu-Jiang,Jiang, Bo
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supporting information
p. 2229 - 2234
(2017/07/07)
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- Towards nitrile-substituted cyclopropanes-a slow-release protocol for safe and scalable applications of diazo acetonitrile
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Diazo acetonitrile has long been neglected despite its high value in organic synthesis due to a high risk of explosions. Herein, we report our efforts towards the transient and safe generation of this diazo compound, its applications in iron catalyzed cyclopropanation and cyclopropenation reactions and the gram-scale synthesis of cyclopropyl nitriles.
- Hock, Katharina J.,Spitzner, Robin,Koenigs, Rene M.
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supporting information
p. 2118 - 2122
(2017/07/24)
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- Asymmetric Nitrone Synthesis via Ligand-Enabled Copper-Catalyzed Cope-Type Hydroamination of Cyclopropene with Oxime
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We report realization of the first enantioselective Cope-type hydroamination of oximes for asymmetric nitrone synthesis. The ligand promoted asymmetric cyclopropene "hydronitronylation" process employs a Cu-based catalytic system and readily available starting materials, operates under mild conditions and displays broad scope and exceptionally high enantio- and diastereocontrol. Preliminary mechanistic studies corroborate a CuI-catalytic profile featuring an olefin metalla-retro-Cope aminocupration process as the key C-N bond forming event. This conceptually novel reactivity enables the first example of highly enantioselective catalytic nitrone formation process and will likely spur further developments that may significantly expedite chiral nitrone synthesis.
- Li, Zhanyu,Zhao, Jinbo,Sun, Baozhen,Zhou, Tingting,Liu, Mingzhu,Liu, Shuang,Zhang, Mengru,Zhang, Qian
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supporting information
p. 11702 - 11705
(2017/09/07)
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- A Metal-Free Oxidative Dehydrogenative Diels–Alder Reaction for Selective Functionalization of Alkylbenzenes
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Functionalization of C(sp3)?H bonds under metal-free reaction conditions is a great challenge due to poor bond reactivity. A novel metal-free oxidative dehydrogenative Diels–Alder reaction of alkylbenzene derivatives with alkenes through C(sp3)?H bond functionalization is described. The developed oxidative method provides a straightforward approach to biologically relevant 1,4-phenanthraquinone and isoindole derivatives from readily available starting materials. Furthermore, the synthesis of nitrostyrenes from enylbenzene derivatives by selective C(sp3)?H bond functionalization has been demonstrated.
- Manna, Srimanta,Antonchick, Andrey P.
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supporting information
p. 7825 - 7829
(2017/06/06)
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- Rapid access to cyclopentadiene derivatives through gold-catalyzed cycloisomerization of ynamides with cyclopropenes by preferential activation of alkenes over alkynes
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In this communication, gold-catalyzed intermolecular cycloisomerization of cyclopropenes and ynamides is investigated. The current transformation displayed an activation priority of double bonds over triple bonds by the cationic gold catalyst, giving the corresponding cyclopentadienes in good to excellent yields. Additionally, this protocol can be expanded to a one-pot two-step procedure for the synthesis of substituted cyclopentanones.
- Cheng, Xing,Zhu, Lei,Lin, Meijun,Chen, Jianxin,Huang, Xueliang
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supporting information
p. 3745 - 3748
(2017/04/03)
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- Iodine-Catalyzed Facile Approach to Sulfones Employing TosMIC as a Sulfonylating Agent
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A novel iodine-catalyzed functionalization of a variety of olefins and alkynes and direct decarboxylative functionalization of cinnamic and propiolic acids with TosMIC to provide access to various vinyl, allyl, and β-iodo vinylsulfones is described. This simple, efficient, and environmentally benign approach employing inexpensive molecular iodine as a catalyst demonstrates a versatile protocol for the synthesis of highly valuable sulfones, rendering it attractive to both synthetic and medicinal chemistry.
- Kadari, Lingaswamy,Palakodety, Radha Krishna,Yallapragada, Lakshmi Prapurna
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supporting information
p. 2580 - 2583
(2017/05/24)
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- Organic base-catalysed solvent-tuned chemoselective carbotrifluoromethylation and oxytrifluoromethylation of unactivated alkenes
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An unprecedented and efficient organic base-catalysed highly chemoselective carbo- and oxytrifluoromethylation of unactivated alkenes with Togni's reagent was developed. The switchable chemoselectivity was tuned by simply changing the organic base catalyst and solvent. Mechanistic studies indicated that a radical cyclization pathway for carbotrifluoromethylation in DMSO and a carbocation pathway for oxytrifluoromethylation in DCE were probably involved.
- Yang, Ning-Yuan,Li, Zhong-Liang,Ye, Liu,Tan, Bin,Liu, Xin-Yuan
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supporting information
p. 9052 - 9055
(2016/07/21)
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- Iodothiocyanation/Nitration of Allenes with Potassium Thiocyanate/Silver Nitrite and Iodine
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Direct strategies for the iodothiocyanation and iodonitration of allenes have been developed. In this process, potassium thiocyanate/silver nitrite and molecular iodine are used as the source of SCN, ONO2and iodine to provide the desired products in moderate to good yields with high stereoselectivity. (Figure presented.).
- Yang, Xiaodong,She, Yue,Chong, Ya,Zhai, Huichun,Zhu, He,Chen, Baohua,Huang, Guosheng,Yan, Rulong
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supporting information
p. 3130 - 3134
(2016/10/09)
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- Synthesis of Terephthalic Acid by p-Cymene Oxidation using Oxygen: Toward a More Sustainable Production of Bio-Polyethylene Terephthalate
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The synthesis of terephthalic acid from biomass remains an unsolved challenge. In this study, we conducted the selective oxidation of p-cymene (synthesized from biodegradable terpenes, limonene, or eucalyptol) into terephthalic acid over a Mn–Fe mixed-oxide heterogeneous catalyst. The impact of various process parameters (oxidant, temperature, reaction time, catalyst amount, oxygen pressure) on the selectivity to terephthalic acid was evaluated, and some mechanistic aspects were elucidated. An unprecedented synthesis of biobased terephthalic acid (51 % yield) in the presence of O2 is reported.
- Nea?u, Florentina,Culic?, Geanina,Florea, Mihaela,Parvulescu, Vasile I.,Cavani, Fabrizio
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p. 3102 - 3112
(2016/11/17)
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- Direct Olefination of Alcohols with Sulfones by Using Heterogeneous Platinum Catalysts
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Carbon-supported Pt nanoparticles (Pt/C) were found to be effective heterogeneous catalysts for the direct Julia olefination of alcohols in the presence of sulfones and KOtBu under oxidant-free conditions. Primary alcohols, including aryl, aliphatic, allyl, and heterocyclic alcohols, underwent olefination with dimethyl sulfone and aryl alkyl sulfones to give terminal and internal olefins, respectively. Secondary alcohols underwent methylenation with dimethyl sulfone. Under 2.5 bar H2, the same reaction system was effective for the transformation of alcohol OH groups to alkyl groups. Structural and mechanistic studies of the terminal olefination system suggested that Pt0 sites on the Pt metal particles are responsible for the rate-limiting dehydrogenation of alcohols and that KOtBu may deprotonate the sulfone reagent. The Pt/C catalyst was reusable after the olefination, and this method showed a higher turnover number (TON) and a wider substrate scope than previously reported methods, which demonstrates the high catalytic efficiency of the present method. Olefination of alcohols: The first heterogeneous catalytic terminal and internal olefination of primary alcohols and methylenation of secondary alcohols with sulfones, a reusable carbon-supported Pt catalyst, and KOtBu is reported (see scheme).
- Hakim Siddiki,Touchy, Abeda Sultana,Kon, Kenichi,Shimizu, Ken-Ichi
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p. 6111 - 6119
(2016/04/26)
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- Iron-Catalyzed Cross-Coupling of Alkenyl Acetates
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Stable C-O linkages are generally unreactive in cross-coupling reactions which mostly employ more electrophilic halides or activated esters (triflates, tosylates). Acetates are cheap and easily accessible electrophiles but have not been used in cross-couplings because the strong C-O bond and high propensity to engage in unwanted acetylation and deprotonation. Reported herein is a selective iron-catalyzed cross-coupling of diverse alkenyl acetates, and it operates under mild reaction conditions (0 C, 2 h) with a ligand-free catalyst (1-2 mol%). Iron clad: Acetates are underutilized electrophiles in metal-catalyzed cross-coupling reactions because of the strong alkenyl C-O bond and their propensity to engage in unwanted reactions. Combination of a ligand-free low-valent Fe catalyst with nucleophilic organomagnesium reagents, low temperature, and short reaction times results in highly selective cross-couplings with alkenyl acetates.
- G?rtner, Dominik,Stein, André Luiz,Grupe, Sabine,Arp, Johannes,Von Wangelin, Axel Jacobi
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supporting information
p. 10545 - 10549
(2015/09/02)
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- Synthesis of 2,5-Diaryl-1,5-dienes from Allylic Bromides Using Visible-Light Photoredox Catalysis
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Visible-light photoreductive coupling of 2-arylallyl bromides in the presence of the photocatalyst Ru(bpy)3(PF6)2, a Hantzsch ester, and i-Pr2NEt gives 2,5-diaryl-1,5-dienes in high yield. This method avoids the use of stoichiometric metal reductants and is compatible with the presence of halogen, alkyl, electron-donating, and electron-withdrawing substituents on the aromatic ring.
- Pratsch, Gerald,Overman, Larry E.
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p. 11388 - 11397
(2015/12/01)
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- Iridium-Catalyzed Enantioselective Hydrogenation of β,β-Disubstituted Nitroalkenes
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A highly efficient, iridium-catalyzed, enantioselective hydrogenation of β,β-disubstituted nitroalkenes has been developed. Using a complex consisting of iridium and (S,S)-f-spiroPhos as the catalyst, a variety of β,β-disubstituted nitroalkenes were successfully hydrogenated to the corresponding chiral nitroalkanes with excellent enantioselectivities (up to 98% ee) and high turnover numbers (TON=1000).
- Liu, Man,Kong, Duanyang,Li, Meina,Zi, Guofu,Hou, Guohua
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supporting information
p. 3875 - 3879
(2016/01/25)
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- DICARBOXYLIC ACID MONOMERS AND METHODS OF MAKING AND USING THE SAME
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Disclosed herein are phenylindane dicarboxylic acid (PIDA) monomers, polymer compositions comprising the PIDA monomers, and methods of preparing PIDA monomers. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present disclosure.
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Paragraph 0297; 0298; 0299
(2015/12/07)
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- A rhodium(I)-catalysed formal intramolecular C-C/C-H bond metathesis
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Phenylcyclobutanes underwent skeletal reorganisation in the presence of Wilkinson's catalyst to afford indanes through a cascade process involving chelation-assisted C-C bond cleavage and intramolecular C-H bond cleavage.
- Matsuda, Takanori,Yuihara, Itaru
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supporting information
p. 7393 - 7396
(2015/04/27)
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- Catalytic enantioselective iodoaminocyclization of hydrazones
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The first catalytic enantioselective iodoaminocyclization of β,γ-unsaturated hydrazones has been developed with the help of a trans-1,2-diaminocyclohexane-derived bifunctional thiourea catalyst and allows for the direct access to δ2-pyrazolines containing a quaternary stereogenic center in high yield with good enantioselectivity (up to 95% yield and 95:5 er).
- Tripathi, Chandra Bhushan,Mukherjee, Santanu
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supporting information
p. 3368 - 3371
(2014/07/08)
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- Direct catalytic olefination of alcohols with sulfones
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The synthesis of terminal as well as internal olefins was achieved by the one-step olefination of alcohols with sulfones catalyzed by a ruthenium pincer complex. Furthermore performing the reaction with dimethyl sulfone under mild hydrogen pressure provides a direct route for the replacement of alcohol hydroxy groups by methyl groups in one step.
- Srimani, Dipankar,Leitus, Gregory,Ben-David, Yehoshoa,Milstein, David
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supporting information
p. 11092 - 11095
(2015/03/30)
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