- Heterocyclization involving benzylic C(sp3)-H functionalization enabled by visible light photoredox catalysis
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A general and efficient method for heterocyclization involving benzylic C(sp3)-H functionalization enabled by visible light photoredox catalysis to access a wide range of structurally diverse oxygen as well as nitrogen heterocycles up to a gram scale is reported. The potential application of this new methodology is demonstrated by the total synthesis of (-)-codonopsinine and (+)-centrolobine. Herein it is proposed that selectfluor, unlike a fluorinating reagent, acts as an oxidative quencher and a hydrogen radical acceptor.
- Pandey, Ganesh,Laha, Ramkrishna,Mondal, Pradip Kumar
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p. 9689 - 9692
(2019/08/15)
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- Aryl Boronic Acid Catalysed Dehydrative Substitution of Benzylic Alcohols for C?O Bond Formation
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A combination of pentafluorophenylboronic acid and oxalic acid catalyses the dehydrative substitution of benzylic alcohols with a second alcohol to form new C?O bonds. This method has been applied to the intermolecular substitution of benzylic alcohols to form symmetrical ethers, intramolecular cyclisations of diols to form aryl-substituted tetrahydrofuran and tetrahydropyran derivatives, and intermolecular crossed-etherification reactions between two different alcohols. Mechanistic control experiments have identified a potential catalytic intermediate formed between the aryl boronic acid and oxalic acid.
- Estopi?á-Durán, Susana,Donnelly, Liam J.,Mclean, Euan B.,Hockin, Bryony M.,Slawin, Alexandra M. Z.,Taylor, James E.
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p. 3950 - 3956
(2019/02/16)
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- A Re2O7catalyzed cycloetherification of monoallylic diols
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A Re2O7catalyzed cycloetherification of monoallylic diols is described. The reaction features short reaction time, mild reaction conditions and exclusive E selectivity. A wide range of monoallylic alcohols with alkyl or aryl substituents on olefin smoothly undergo ring closure to deliver corresponding oxa-heterocycles. The reaction is also operationally simple and not sensitive to air and moisture.
- Wan, Xiaolong,Hu, Jiadong,Xu, Dongyang,Shang, Yang,Zhen, Yanxia,Hu, Chenchen,Xiao, Fan,He, Yu-Peng,Lai, Yisheng,Xie, Weiqing
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p. 1090 - 1093
(2017/03/02)
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- Cyclic ether synthesis from diols using trimethyl phosphate
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Cyclic ethers have been effectively synthesized via the intramolecular cyclization of diols using trimethyl phosphate and NaH. The present cyclization could proceed at room temperature to produce 5-7 membered cyclic ethers in good to excellent yields. Substrates possessing a chiral secondary hydroxy group were transformed into the corresponding chiral cyclic ethers along with the retention of their stereochemistries.
- Asai, Shota,Kato, Maho,Monguchi, Yasunari,Sajiki, Hironao,Sawama, Yoshinari
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supporting information
p. 4787 - 4790
(2017/07/06)
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- Mn-catalyzed three-component reactions of imines/nitriles, grignard reagents, and tetrahydrofuran: An expedient access to 1,5-amino/keto alcohols
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An expedient Mn-catalyzed three-component synthesis of 1,5-amino/keto alcohols from Grignard reagents, imines/nitriles, and tetrahydrofuran (THF) is described, which deviates from the classic Grignard addition to imines/nitriles in THF solvent. THF is split and sewn in an unprecedented manner in the reaction, leading to the formation of two geminal C-C bonds via C-H and C-O cleavage. Mechanistic experiments and DFT calculations reveal radical and organo-Mn intermediates in the catalytic cycle and the α-arylative ring-opening of THF as the key reaction step.
- He, Ruoyu,Jin, Xiqing,Chen, Hui,Huang, Zhi-Tang,Zheng, Qi-Yu,Wang, Congyang
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p. 6558 - 6561
(2014/05/20)
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- Ligand-controlled, norbornene-mediated, regio- and diastereoselective rhodium-catalyzed intramolecular alkene hydrosilylation reactions
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Ligand-controlled, norbornene-mediated, regio- and diastereoselective rhodium-catalyzed intramolecular alkene hydrosilylation of homoallyl silyl ethers (1) exploiting either BINAP or 1,6-bis(diphenylphosphino)hexane (dpph) has been developed. This method
- Hua, Yuanda,Nguyen, Hiep H.,Scaggs, William R.,Jeon, Junha
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supporting information
p. 3412 - 3415
(2013/07/26)
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- Boronic acid catalysis as a mild and versatile strategy for direct carbo- and heterocyclizations of free allylic alcohols
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BAC to the future: Boronic acid catalysis (BAC) was applied to the direct activation of alcohols leading to the preparation of carbocycles (see scheme), benzofurans, tetrahydrofurans, pyrrolidines, pyrans, piperidines, and various polycyclic compounds. The reactions proceed under mild conditions that circumvent the use of reactive leaving groups like halides. Copyright
- Zheng, Hongchao,Ghanbari, Sina,Nakamura, Shinji,Hall, Dennis G.
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supporting information; experimental part
p. 6187 - 6190
(2012/08/13)
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- Gold-catalysed cyclic ether formation from diols
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Gold(I) and (III) salts have been found to be highly effective at the catalysis of ether formation from alcohols. Intramolecular ether formation of a 1,5-diol was also achieved, with a stereoselectivity that indicates that an SN1 mechanism predominates. In an attempt to form a seven-membered ring, a stable 14-membered dimer product was also formed. Attempts to control the diastereoselectivity of the reaction using a chiral anionic counterion did not give products with a high de.
- Jiang, Xiaolu,London, Emma K.,Morris, David J.,Clarkson, Guy J.,Wills, Martin
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experimental part
p. 9828 - 9834
(2011/02/23)
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- Systematic investigations on the reduction of 4-aryl-4-oxoesters to 1-aryl-1,4-butanediols with methanolic sodium borohydride
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4-Aryl-4-oxoesters undergo facile reduction of both the keto and the ester groups with methanolic NaBH4 at room temperature to yield the corresponding 1-aryl-1,4-butanediols whereas 4-alkyl-4-oxoesters furnish the corresponding 1,4-butanolides via selective reduction of the keto moiety. Results of a detailed and systematic investigation of the reaction are described.
- Chaudhuri, Subrata Kumar,Saha, Manabendra,Saha, Amit,Bhar, Sanjay
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supporting information; experimental part
p. 748 - 755
(2011/01/03)
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- Application of a one-pot lipase resolution strategy for the synthesis of chiral γ- and δ-lactones
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A successful one-pot reduction of γ-ketoesters, δ-ketoesters and lactones to the corresponding 1,4- and 1,5-diols followed by a lipase catalyzed kinetic resolution coupled with hydrolysis to afford optically active diols is described. The synthetic utility of this one-pot method was illustrated by the oxidation of these chiral diols to respective chiral γ-butyrolactone and δ-lactones. Lipase from Pseudomonas cepacia, immobilized on ceramic afforded the product with high enantiomeric excess in good yields under mild reaction conditions. This approach has been used to develop a convenient enantioselective route for several γ- and δ-lactones using achiral and corresponding racemic starting material.
- Kamal, Ahmed,Sandbhor, Mahendra,Shaik, Ahmad Ali
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p. 1575 - 1580
(2007/10/03)
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- Process for the production of cyclic sulfonium salts
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A process for the production of a 5-7 membered ring cyclic sulfonium salt compound, including a 5-7 membered ring cyclic sulfonium salt compound having a non-nucleophilic anion, is described. Members of the latter group are potentially useful as initiators for cationic polymerizations. The process comprises reacting a 1.4-, 1.5-, or 1.6-diol compound or a 5-7 membered ring cyclic ether compound with a mercapto compound and a strong protonic acid yielding the cyclic sulfonium salt compound. Some compounds described are also novel compounds per se.
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- γ-Lithioalkoxides via Reductive Lithiation of Oxetanes by Aromatic Radical Anions
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Oxetanes are cleaved at 0 deg C in tetrahydrofuran by lithium 4,4'-di-tert-butylbiphenylide, giving lithium γ-lithioalkoxides which can provide 2-substituted tetrahydrofurans by trapping with aldehydes and ketones followed by acid cyclization of the resulting 1,4-diols; the cuprates of these dianions undergo conjugate addition and nucleophilic substitution reactions.
- Mudryk, Boguslaw,Cohen, Theodore
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p. 5657 - 5659
(2007/10/02)
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- Ring Transformation of 2-Furylcarbamates to 5-Hydroxy-3-pyrrolin-2-ones. Effects of Substitution in the Benzene Ring on the N-Carbobenzyloxy-5-hydroxy-5-phenyl-3-pyrroline-2-one -- cis-γ-Ketoamide Equilibrium
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In the ring transformation of 2-furylcarbamates (2) to 5-hydroxy-3-pyrrolin-2-ones (3) by irradiation in the presence of oxygen, there is an equilibrium between N-carbobenzyloxy-5-hydroxy-5-phenyl-3-pyrrolin-2-one (3-A) and cis-γ-ketoamide (3-B); this equ
- Yakushijin, Kenichi,Kozuka, Masamichi,Morishita, Takayuki,Furukawa, Hiroshi
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p. 2420 - 2430
(2007/10/02)
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