TiCl4, Dioxane—A Facile and Efficient System for De-O-Benzylation, De-O-Allylation, and De-O-Xylylation of Phenolic Ethers

Rajakumar, Perumal; Murali, Venghatraghavan

doi:10.1081/scc-120026311

Cited by 13 publications

(5 citation statements)

References 26 publications

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“…It was not possible to use non-nucleophilic tertiary nitrogen bases such as triethylamine for the known reactivity of the trialkyl amines with TiCl 4 [ 39 , 40 ]. The reaction was designed in dichloromethane excluding ethereal solvents such as THF because, in the presence of TiCl 4 , O-heterocycle ring opening reaction occurs [ 41 , 42 ]. Therefore the amidation reaction was carried out in dichloromethane under reflux by treating benzoic acid (1 mmol) with pyridine (1 mmol) and TiCl 4 (1.5 mmol), then aniline was added (1 mmol).…”

Section: Resultsmentioning

confidence: 99%

Formation of amides: one-pot condensation of carboxylic acids and amines mediated by TiCl4

Leggio

Bagalà

Belsito

et al. 2017

Chemistry Central Journal

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A general procedure for the synthesis of amides via the direct condensation of carboxylic acids and amines in the presence of TiCl4 is reported. The amidation reaction was performed in pyridine at 85 °C with a wide range of substrates providing the corresponding amide products in moderate to excellent yields and high purity. The reaction proceeds with low yields when both the carboxylic acid and the amine are sterically hindered. The process takes place with nearly complete preservation of the stereochemical integrity of chiral substrates.Electronic supplementary materialThe online version of this article (doi:10.1186/s13065-017-0318-9) contains supplementary material, which is available to authorized users.

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Section: Resultsmentioning

confidence: 99%

Formation of amides: one-pot condensation of carboxylic acids and amines mediated by TiCl4

Leggio

Bagalà

Belsito

et al. 2017

Chemistry Central Journal

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“…Since the allyl group had to be preserved for later incorporation of a spacer moiety, the benzyl groups had to be removed by other alternative routes than hydrogenolysis. Gratifyingly, treatment of peracetate 34 with TiCl 4 lead to smooth cleavage of the benzylic protecting groups [27]. For ease of purification, resulting diol was acetylated to eventually give the hexa- O -acetyl compound 39 in 89% combined yield.…”

Section: Synthesis Of Ara4n-(1→8)-ko Related To Burkholderia Lpsmentioning

confidence: 99%

Synthesis of lipid A and inner-core lipopolysaccharide (LPS) ligands containing 4-amino-4-deoxy-L-arabinose units

Zamyatina

Hollaus

Blaukopf

et al. 2011

Pure and Applied Chemistry

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Attachment of 4-amino-4-deoxy-L-arabinose to phosphates or sugar hydroxyl groups of lipopolysaccharide contributes to bacterial resistance against common antibiotics. For a detailed study of antigenic properties and binding interactions, Ara4N-containing inner core ligands related to Burkholderia and Proteus LPS have been synthesized in good yields. Glycosylation at position 8 of allyl glycosides of oct-2-ulosonic acids (Ko, Kdo) has been accomplished using an Nphenyltrifluoroacetimidate 4-azido-4-deoxy-L-arabinosyl glycosyl donor followed by azide reduction and global deprotection. The β-L-Ara4N-(1→8)-α-Kdo disaccharide was further extended into the branched β-L-Ara4N-(1→8)[α-Kdo-(2→4)]-α-Kdo trisaccharide via a regioselective glycosylation of a protected triol intermediate. Synthesis of Ara4N-modified lipid A -part structure occurring in the LPS of Burkholderia, Pseudomonas and Klebsiellla strains was accomplished using the H-phosphonate approach. The stereocontrolled assembly of the phosphodiester linkage connecting glycosidic centres of two aminosugars was elaborated employing an anomeric H-phosphonate of cyclic silyl-ether protected 4-azido-4-deoxy-β-Larabinose which was coupled to the hemiacetal of the lipid A GlcN-disaccharide backbone. Conditions for global deprotection which warrant the integrity of "double anomeric" phosphodiester linkage were successfully developed. Introduction of thiol-terminated spacer at the synthetic ligands allows both coupling to BSA and immobilization on gold nanoparticles as well as generation of glycoarrays.

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“…The p -methylbenzyl (MBn) group is an uncommon analogue of the benzyl protecting group family. It has been used for the protection of phenols and carbohydrates, and its deprotection proceeds similar to that of the Bn group under hydrogenolysis − ,, and with the use of a Lewis acid. , Additionally, a trifluoroacetic acid (TFA) cocktail (2% each of H 2 O, ethanedithiol, and triisopropylsilane in TFA) enables its removal, indicating that it is weaker than the Bn group (Scheme a). Further, results suggesting potential oxidative removal of the MBn group have been reported (Scheme b,c), − highlighting the possibilities for deprotection of this group using multiple approaches.…”

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confidence: 99%

p-Methylbenzyl Group: Oxidative Removal and Orthogonal Alcohol Deprotection

et al. 2019

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We describe the practical removal of pmethylbenzyl (MBn) protections of alcohols by treatment with 2,3-dichloro-5,6-dicyano-p-benzoquinone. When a molecule bears benzyl and MBn groups, the oxidant selectively removes the latter groups. Further, the MBn groups tolerate ceric ammonium nitrate, resulting in chemoselective removal of the p-methoxybenzyl group in the presence of the MBn groups. These orthogonal alcohol deprotections would provide novel synthetic strategies of organic compounds.

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TiCl₄, Dioxane—A Facile and Efficient System for De-O-Benzylation, De-O-Allylation, and De-O-Xylylation of Phenolic Ethers

Cited by 13 publications

References 26 publications

Formation of amides: one-pot condensation of carboxylic acids and amines mediated by TiCl4

Formation of amides: one-pot condensation of carboxylic acids and amines mediated by TiCl4

Synthesis of lipid A and inner-core lipopolysaccharide (LPS) ligands containing 4-amino-4-deoxy-L-arabinose units

p-Methylbenzyl Group: Oxidative Removal and Orthogonal Alcohol Deprotection

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