- Photoreductive Removal of O-Benzyl Groups from Oxyarene N-Heterocycles Assisted by O-Pyridine-pyridone Tautomerism
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Facile photoreductive protocols have been developed to remove benzyl O-protective groups from oxyarene N-heterocycles at positions capable for 2-/4-O-pyridine-2-/4-pyridone tautomerism. Blue light irradiation, a [Ru] or [Ir] photocatalyst, and ascorbic acid in a water-acetonitrile solution debenzylates a variety of aryl N-heterocycles cleanly and selectively. Ascorbic acid has two functions in the reaction. On the one hand, it protonates the N-heterocycles that reduces their reduction potentials notably and on the other hand it acts as a sacrificial reductant. Reduction potentials and free energy barriers calculated at the CPCM-B3LYP/6-31+G? level can predict the reactivities of the studied substrates.
- Todorov, Aleksandar R.,Wirtanen, Tom,Helaja, Juho
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p. 13756 - 13767
(2017/12/26)
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- Selectivity of N-versus O-alkylation in Mitsunobu reactions with various quinolinols and isoquinolinols
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Reacting quinolinols and isoquinolinols under Mitsunobu conditions can give rise to N-alkylated products in addition to the normally desired O-alkylated structures. An in-depth study of how the solvent, reagent equivalents, position of the quinoline/isoqu
- Hartung, Ryan E.,Wall, Mark C.,Lebreton, Sylvain,Smrcina, Martin,Patek, Marcel
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p. 1305 - 1313
(2017/07/18)
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- Tetrabutyl ammonium bromide-mediated benzylation of phenols in water under mild condition
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Benzylation of phenol was successfully achieved in water under room temperature mediated by tetrabutylammonium bromide (TBAB) for only 2 h affording the corresponding benzyl phenyl ether with good to excellent yields. This protocol is very efficient, simple, avoiding catalysts, easy to work-up after reaction, and especially 'green'.
- Wang, Hailei,Ma, Yuping,Tian, Heng,Yu, Ajuan,Chang, Junbiao,Wu, Yangjie
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p. 2669 - 2673
(2014/04/03)
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- Cesium fluoride-Celite: A solid base for efficient syntheses of aromatic esters and ethers
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Coupling reactions of a number of aromatic and heteroaromatic phenols with alkyl, acyl or benzoyl halides in acetonitrile with cesium fluoride-Celite are described, demonstrating that this reagent provides an efficient, convenient and practical method for the syntheses of aromatic esters and ethers.
- Shah, Syed Tasadaque Ali,Khan, Khalid Mohammed,Hussain, Hidayat,Anwar, Muhammad Usman,Fecker, Miriam,Voelter, Wolfgang
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p. 6652 - 6656
(2007/10/03)
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- An efficient approach towards syntheses of ethers and esters using CsF-Celite as a solid base
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The coupling reactions of a number of alcohols and phenols with alkyl, acyl or benzoyl halides in acetonitrile with cesium fluoride-Celite are described. It has been found that CsF-Celite combinations provide an efficient, convenient and practical method for syntheses of both, ethers and esters.
- Shah, Syed Tasadaque A,Khan, Khalid M,Heinrich, Angelica M,Choudhary, M.Iqbal,Voelter
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p. 8603 - 8606
(2007/10/03)
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- Kinetics of Benzylation of Hydroxypyridines & Hydroxyquinolines in Dimethyl Sulphoxide - Water & Isopropanol - Water Mixtures
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The kinetics of benzylation of hydroxypyridines and hydroxyquinolines have been investigated in DMSO-water and isopropanol-water mixtures.A formal comparison of rate of benzylation of phenols and naphthols has also been made.DMSO, being a dipolar aprotic solvent facilitates O-alkylation of phenols and naphthols and a considerable rate increase has been observed in DMSO-water, giving the O-alkylated products in more than 90percent yield in both the cases.However, in the case of benzylation of hydroxypyridine in DMSO-water, O-alkylated product formed is only 65percent and the magnitude of rate increase, compared to phenols and naphthols, is much less, under similar conditions.But the rate of benzylation of 8-hydroxyquinoline in DMSO-water is retarded considerably and the rate is even slower than the rate of N-benzylation of quinoline, indicating only O-benzylation of 8-hydroxyquinoline in DMSO-water is unique and is mainly due to greater ground state solvation of substrate by DMSO, a factor which has been considered insignificant in all the other cases.
- Rajasekar, N.,Srinivasan, V. S.,Venkatasubramanian, N.
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p. 800 - 802
(2007/10/02)
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