- Manganese- and Borane-Mediated Synthesis of Isobenzofuranones from Aromatic Esters and Oxiranes via C-H Bond Activation
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A manganese- and borane-mediated synthesis of isobenzofuranones from esters and oxiranes is developed. The reaction proceeded at aromatic, heteroaromatic, and olefinic C-H bonds with high functional group tolerance. This is the first example of a manganese-catalyzed C-H transformation using an oxygen-directing group. Triphenylborane played an important role in this reaction to cooperatively promote the annulation reaction. Kinetic isotope effect experiments revealed that C-H bond activation of the aromatic rings was the rate-determining step.
- Sueki, Shunsuke,Wang, Zijia,Kuninobu, Yoichiro
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- Synthesis of 1,2-phenylenedimethanols by base-promoted reduction of isobenzofuran-1(3H)-ones with silane
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An efficient method for preparation of substituted 1,2-phenylenedimethanols and aliphatic 1,4-diols that are valuable intermediates in organic synthesis, has been developed by the base-promoted reduction of isobenzofuran-1(3H)-ones and γ-lactones with silane under mild conditions. Compared with traditional procedures using stoichiometric amounts of metal hydrides and alkyl reductants, the present method avoids the use of sensitive reagents and is operationally simple and a broad variety of functional groups are tolerated.
- Liu, Bin,Zhou, Xigeng
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supporting information
p. 725 - 728
(2018/12/11)
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- Titanocene(III) chloride mediated radical induced synthesis of isobenzofuranones via allylation of aldehydes followed by in situ lactonization
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Titanocene(III) chloride mediated radical induced synthesis of isobenzofuranones has been accomplished via allylation of aldehydes followed by in situ lactonization in good yield. The radical initiator titanocene(III) chloride (Cp2TiCl) has been prepared from commercially available Cp2TiCl2 and Zn dust in THF under argon.
- Mukherjee, Shirshendu,Roy, Subhas Chandra
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- Mechanistic analysis of a copper-catalyzed C-H oxidative cyclization of carboxylic acids
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We recently reported that carboxylic acids can be oxidized to lactone products by potassium persulfate and catalytic copper acetate. Here, we unravel the mechanism for this C-H functionalization reaction using desorption electrospray ionization, online electrospray ionization, and tandem mass spectrometry. Our findings suggest that electron transfer from a transient benzylic radical intermediate reduces Cu(ii) to Cu(i), which is then re-oxidized to Cu(ii) in the catalytic cycle. The resulting benzylic carbocation is trapped by the pendant carboxylate group to give the lactone product. Formation of the putative benzylic carbocation is supported by Hammett analysis. The proposed mechanism for this copper-catalyzed oxidative cyclization process differs from earlier reports of analogous reactions, which posit a substrate carboxylate radical as the reactive oxidant.
- Banerjee, Shibdas,Sathyamoorthi, Shyam,Du Bois,Zare, Richard N.
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p. 7003 - 7008
(2017/10/05)
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- Domino [Pd]-Catalysis: One-Pot Synthesis of Isobenzofuran-1(3H)-ones
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An efficient domino [Pd]-catalysis for the synthesis of isobenzofuran-1(3H)-ones is presented. The strategy shows broad substrate scope and is amenable to o-bromobenzyl tertiary/secondary/primary alcohols. Significantly, the method was applied to the synthesis of antiplatelet drug n-butyl phthalide and cytotoxic agonist 3a-[4′-methoxylbenzyl]-5,7-dimethoxyphthalide.
- Mahendar, Lodi,Satyanarayana, Gedu
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p. 7685 - 7691
(2016/09/09)
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- Formation of 2-arylindane-1,3-diones and 3-alkylphthalides from methyl o-[α-phenylsulfonyl]toluate
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2-Aryl-1,3-indanedione and phthalide derivatives have attracted considerable interest due to their anticoagulant, parasiticidal and a range of biological activities. The synthesis of 2-aryl-1,3-indanedione by the condensation of the title sulfone with aryl aldehydes through an interesting pathway and a previously unreported approach to 3-alkylphthalide from C-alkylated derivatives of 1 under microwave and conventional heating conditions are described.
- Thirumamagal,Narayanasamy, Sureshbabu
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p. 512 - 515
(2008/04/13)
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- Highly efficient cyclization of o-iodobenzoates with aldehydes catalyzed by cobalt bidentate phosphine complexes: A novel entry to chiral phthalides
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Methyl 2-iodobenzoates 1a-c undergo cyclization reactions with various aromatic aldehydes 2a-m (RC6CHO: R = H 2a, 4-CH3, 2b, 4tBu 2c, 4-OMe 2d, 3-OMe 2e, 4-C1 2f, 4-CF3 2g, 4-CN 2h, 4-Ph 2i; benzo [d][1,3]dioxole-5-carbaldehyde (2j), 1napthaldehyde (2k), benzofuran-2- carbaldehyde (21), and isonicotinaldehyde (2m)) in the presence of [CoI2(dppe)] (dppe = l,2-bis(diphenylphosphino)ethane) and Zn powder in dry THF at 75 °C for 24 h to give the corresponding phthalide derivatives 3a-m and 3q-t in good to excellent yields. Under similar reaction conditions, less reactive aliphatic aldehydes, heptanal (2n), butyraldehyde (2o), and 2-phenylacetaldehyde (2p) also underwent cyclization reactions with la to provide 3n-p, respectively, in fair to good yields. The catalytic reaction can be further extended to cinnamyl aldehyde (2q) with la to give the corresponding phthalide derivative 3u. This synthetic method is compatible with a variety of functional groups on the aryl ring of 2. The high efficiency of the cobalt catalyst containing a dppe (dppe = l,2-bis(diphenylphosphino)ethane) ligand encouraged us to investigate the asymmetric version of the present catalytic reaction by employing bidentate chiral ligands. Thus, aromatic aldehydes 2a-c, 2f, and 2 g undergo cyclization with 2-iodobenzoate (la) smoothly in the presence of [CoI2{(S,S)- dipamp}] ((S,S)-dipamp = (1S,2S)-(+)-bis[2-methoxyphenyl]phenylphosphino)ethane) and zinc powder in THF at 75 °C for 24 h, giving the corresponding (S)-phthalides 4a-e in 8189 % yields with 70-98 % ee. A possible mechanism for the present catalytic reaction is proposed.
- Chang, Hong-Tai,Jeganmohan, Masilamani,Cheng, Chien-Hong
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p. 4356 - 4363
(2008/02/05)
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- Direct lactone formation by using hypervalent iodine(III) reagents with KBr via selective C-H abstraction protocol
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We have developed a new and reliable method for the direct construction of biologically important aryl lactones and phthalides from carboxylic and benzoic acids, using a combination of hypervalent iodine(III) reagents with KBr.
- Dohi, Toshifumi,Takenaga, Naoko,Goto, Akihiro,Maruyama, Akinobu,Kita, Yasuyuki
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p. 3129 - 3132
(2008/02/09)
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- A new entry for the preparation of substituted aromatic carbonyl compounds mediated by Samarium(II) iodide
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A new route to substituted aromatic lactones and lactams via SMI2-promoted desulfurization is described. Direct replacement of the phenylthio substituent by hydroxyalkylated groups featuring the novel accessible process for the construction of continuous quaternary carbon centers could be accomplished when the same type of reactions was undertaken with carbonyl compounds in the presence of SmI2.
- Yoda, Hidemi,Kohata, Naoki,Takabe, Kunihiko
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p. 1087 - 1094
(2007/10/03)
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- Thionation of ω-hydroxy amides with Lawesson's reagent: Synthesis of thioenamides and sulfur-containing heterocycles
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The thionation of ω-hydroxy amides with Lawesson's reagent [LR: 2,4- bis(p-methoxyphenyl)-1,3,2,4-dithiaphosphetane-2,4-disulfide] is described. The treatment of 3-hydroxy amides 1 with LR exclusively gave thioenamides 2 in fair yields. The treatment of 4-hydroxy amides 5 with LR yielded sulfur- containing heterocycles such as tetrahydrothiophene-2-imines 6 and tetrahydrothiophene-2-thione 7a through cyclization of intermediates, 4- mercapto amides 8. The 5-hydroxy amides 13 also reacted with LR to afford tetrahydrothiopyrane-2-thione 14 as the the sole product.
- Nishio, Takehiko,Sekiguchi, Hiroshi
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p. 5017 - 5026
(2007/10/03)
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- Palladium-catalysed heteroannulation with terminal alkynes: Synthesis of phthalides
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The palladium-copper-catalysed heteroannulation of o-iodobenzoic acid 3 with terminal alkynes 4-18 leads to the synthesis of (Z)-3-alkylidenephthalides 19-33 as the major products. In certain cases, the formation of isocoumarins 34-37 is also observed.
- Kundu, Nitya G.,Pal, Manojit,Nandi, Bidisha
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p. 561 - 568
(2007/10/03)
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- Regenerative role of the red phosphorus in the couple 'HIaq/Pred'
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The synthesis of ortho-substituted benzoic acid 3 from benzalphthalide 1 in the presence of 'hydriodic acid-red phosphorus' (HIaq/Pred) occurs via the formation of benzylphthalide 2 as reaction intermediate. Its preparation is optimized by use of the 'supported reaction in dry media' process (Silica/HIaq) under microwave irradiation for 8 min. The role of the red phosphorus in the reduction reaction is elucidated: it intervenes in a catalytic cycle by an oxido-reductive disproportionation with the liberated iodine, affording either hypophosphorous acid in aqueous media, or P2I4 in anhydrous media with concomitant regeneration of HI. Thus, the presence of Pred in the couple 'HIaq/Pred' allows recycling of the hydriodic acid and enhances its reducing efficiency.
- Albouy, Dominique,Etemad-Moghadam, Guita,Vinatoru, Mircea,Koenig, Max
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p. 295 - 299
(2007/10/03)
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- Intramolecular Generation of Oxonium Ylides from Functionalized Arylcarbenes
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Arylcarbenes carrying alkoxyalkyl groups in the ortho position have been generated by flash pyrolysis and photolysis of appropriate tosylhydrazone sodium salts.In the gas phase and in a aprotic solvents, interaction of the carbenes with the lone electron pairs of oxygen competes efficiently with insertion into C-H bonds.Both five- and six-membered cyclic oxonium ylides have been generated.The ylides 23, 37, 61b, and 74 undergo 1,2 shifts of benzyl groups with ease, even if ring contraction to highly strained benzocyclobutenes is involved (23, 74).The oxonium ylides37 and 61b strongly prefer the nonconcerted Stevens rearrangement to the sigmatropic Sommelet rearrangement, in contrast to analogous ammonium ylides.Alkyl shifts occur to a very minor extent, if at all.Evidence is presented that alcohols intercept both the carbenes and the oxonium ylides.Protonation of the ylides leads to cyclic oxonium ions, which undergo nucleophilic cleavage of the C-O bonds.Acid catalyzed decomposition of the appropriate diazo compounds gives rise to six-membered, but not to five-membered, cyclic oxonium ions, thus confirming the different intramolecular reactivities of arylcarbenes and benzyl cations.The efficiency of carbene interception increases with increasing acidity of the medium, suggesting nucleophilic behavior (protonation) of the arylcarbenes.
- Kirmse, Wolfgang,Kund, Klaus
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p. 1465 - 1473
(2007/10/02)
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