Expanding the scope of methyl xanthate esters - From Barton-McCombie reaction auxiliary to versatile protective group

Thorsheim, Karin; Manner, Sophie; Ellervik, Ulf

doi:10.1016/j.tet.2017.09.022

Cited by 4 publications

(4 citation statements)

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“…Thermodynamic parameters such as the free energy change (ΔG0), enthalpy change (ΔS0), and entropy change (ΔH0) can be estimated using thermodynamic equations [20,26]. The distribution coefficient Kd (L/g) was determined by the following equation:Kd=qece…”

Section: Resultsmentioning

confidence: 99%

Adsorption of Pb2+ from Aqueous Solutions Using Novel Functionalized Corncobs via Atom Transfer Radical Polymerization

Chen

Zhao

2019

Polymers

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The present study developed novel functionalized corncobs introducing brushes with dense and active carboxyl groups (–COOH), named MC-g-PAA, for the highly efficient adsorption of Pb2+ from aqueous solutions. MC-g-PAA were synthesized via atom transfer radical polymerization (ATRP) and characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The amount of Pb2+ adsorbed on MC-g-PAA by hydrolysis with t-BuOK was 2.28 times greater than that with NaOH, attributed to the larger steric effect of t-BuOK, which reduced the hydrolysis of the bromo-ester groups. The influence of different parameters including the solid/liquid ratio, working solution pH, sorption temperature, and initial concentration and sorption time on the adsorption of Pb2+ were investigated in detail in batch experiments. Thermodynamic studies have shown that the adsorption process was spontaneous, endothermic, and accompanied by an increase in randomness. A better fit for the isotherm data was obtained using the Langmuir model than for the other four models and the maximum amount (qmax) of Pb2+ adsorbed on MC-g-PAA was 342.47 mg/g, which is 21.11 times greater when compared with that of pristine corncobs (16.22 mg/g). The adsorption of Pb2+ on MC-g-PAA was very fast and followed the pseudo-second-order kinetic equation with a correlation coefficient of 0.99999. This monolayer adsorption process was dominated by chemical adsorption, and may proceed according to complexation and electrostatic interactions between Pb2+ and the carboxylate groups. This study indicated that MC-g-PAA could be successfully used as an adsorbent for the removal of Pb2+ from aqueous solutions due to its excellent efficiency.

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Section: Resultsmentioning

confidence: 99%

Adsorption of Pb2+ from Aqueous Solutions Using Novel Functionalized Corncobs via Atom Transfer Radical Polymerization

Chen

Zhao

2019

Polymers

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“…In the synthesis toward the 4-deoxy-4-fluoro analogue 1c , the xanthate group was used as a protective group that facilitated fluorination, similar to the fluorination of 36 . Thus, fluorination of 40 gave the corresponding fluoro analogue 61 in 22% yield together with recovered 40 (47%).…”

Section: Resultsmentioning

confidence: 99%

“…The most common procedure for deoxygenation of a secondary alcohol is the Barton–McCombie method. , Deoxygenation of methyl xanthates is normally performed using a hydride source in combination with a radical initiator. For environmental reasons, hypophosphorous acid with AIBN and Et 3 N was used in these deoxygenations, rather than the more common organic tin hydrides …”

Section: Resultsmentioning

confidence: 99%

“…In the synthesis toward the 4-deoxy-4-fluoro analogue 1c, the xanthate group was used as a protective group 39 Epimerizations. Previous work involving inversions of different positions of naphthoxylosides have involved the Lattrell−Dax reaction with nitrite on positions 3 and 4, triflate displacement with CsOAc on position 2, 9 and Swern oxidation−reduction sequences.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Synthesis of Double-Modified Xyloside Analogues for Probing the β4GalT7 Active Site

et al. 2018

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Monosubstituted naphthoxylosides have been shown to function as substrates for, and inhibitors of, the enzyme β4GalT7, a key enzyme in the biosynthetic pathway leading to glycosaminoglycans and proteoglycans. In this article, we explore the synthesis of 16 xyloside analogues, modified at two different positions, as well as their function as inhibitors of and/or substrates for the enzyme. Seemingly simple compounds turned out to require complex synthetic pathways. A meta-analysis of the synthetic work shows that, regardless of the abundance of methods available for carbohydrate synthesis, even simple modifications can turn out to be problematic, and double modifications present additional challenges due to conformational, steric, and stereoelectronic effects.

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Phenacyl Xanthates: A Photoremovable Protecting Group for Alcohols under Visible Light

Yang

2019

Asian J Org Chem

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The utility of phenacyl xanthates for the protection of hydroxyl groups is reported herein. Phenacyl xanthates are readily prepared via a one‐pot procedure, which employs the commercially available, inexpensive 2‐bromoacetophenone and carbon disulphide. The introduction of phenylcarboxymethyl dithiocarbonates could be achieved in good to excellent yield in the presence of ester group or ketal group. The hydroxyl group can be released in the presence of ethidine under irradiation of visible light without photocatalyst. The phenacyl xanthates could be selectively removed without affecting a series of common protecting groups, such as benzoate, tetrahydropyran and ketal groups. Finally, a plausible mechanism of photocleavage of phenacyl xanthates has been discussed.

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Expanding the scope of methyl xanthate esters - From Barton-McCombie reaction auxiliary to versatile protective group

Cited by 4 publications

References 39 publications

Adsorption of Pb2+ from Aqueous Solutions Using Novel Functionalized Corncobs via Atom Transfer Radical Polymerization

Adsorption of Pb2+ from Aqueous Solutions Using Novel Functionalized Corncobs via Atom Transfer Radical Polymerization

Synthesis of Double-Modified Xyloside Analogues for Probing the β4GalT7 Active Site

Phenacyl Xanthates: A Photoremovable Protecting Group for Alcohols under Visible Light

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