- Sulfonic Acid Functionalized Ordered Mesoporous Silica and their Application as Highly Efficient and Selective Heterogeneous Catalysts in the Formation of 1,2-Monoacetone-D-glucose
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A series of sulfonic acid functionalized ordered mesoporous silica (OMS), designated as RSO3H-OMS (R=alkyl or aryl; OMS=MCM-41, IITM-56 or SBA-15), were prepared by post-synthesis grafting method. These catalysts, in general, exhibit strong acidic sites and, therefore, yield diacetone-D-glucose as main product in the D-glucose acetonation reaction. On the other hand, the functionalized catalyst can also be tuned in such a way to generate significant amount of weak-to-moderate acidic sites, which are in turn responsible for the formation of 1,2-monoacetone-D-glucose, hitherto not reported so far. These functionalized materials also show promise as they are water tolerant catalyst as well as exhibit varying acidic strengths, which allow greater flexibility for the desired product. In addition, the uniform mesopores with high surface area permit bulkier molecules to enter the active sites, thus the catalyst offers larger pliability in terms of yield and reusability. We report here, for the first time, RSO3H-SBA-15, with sizable amount of weak-to-moderate acidic sites, as a robust heterogeneous catalyst for the formation of the targeted molecule, 1,2-monoacetone-D-glucose.
- Krishna, Nunna V.,Anuradha, Sankaran,Ganesh, Reddi,Kumar, Velisoju V.,Selvam, Parasuraman
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- Tetranuclear zinc cluster: A dual purpose catalyst for per-: O -acetylation and de- O -acetylation of carbohydrates
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The trifluoroacetic acid adduct of tetranuclear zinc cluster Zn4(OCOCF3)6O catalysis in per-O-acetylation and de-O-acetylation of carbohydrates at 70 °C can be tuned by adjusting the reaction medium. Per-O-acetylation of hexopyranoses with a near stoichiometric amount of acetic anhydride in toluene resulted in the exclusive formation of pyranosyl products as an anomeric mixture, whereas de-O-acetylation of acetates occurred in methanol in high yields. In the latter, methanol acts as both nucleophile and solvent, and the reaction conditions were compatible to acid- and base-sensitive groups and amino acid derivatives.
- Lin, Ting-Wei,Adak, Avijit K.,Lin, Hong-Jyune,Das, Anindya,Hsiao, Wei-Chen,Kuan, Ting-Chun,Lin, Chun-Cheng
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p. 58749 - 58754
(2016/07/07)
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- Indium(III) triflate: A highly efficient catalyst for reactions of sugars
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Indium(III) trifluoromethanesulfonate has been found to be extremely efficient in catalyzing acyl transfer reactions of various carbohydrates and their derivatives. Selective acetolyses of certain benzyl ethers/isopropylidene acetals of sugars have been possible using In(OTf)3 in Ac2O (neat). Reaction of the per-O-acetate of 2-deoxy-2-phthalimido-D-glucose with benzyl mercaptan in the presence of In(OTf)3 led to the formation of the corresponding thioglycoside in high yield. Facile formation and hydrolysis of the isopropylidene and benzylidene acetals of various carbohydrates have also been achieved very efficiently in the presence of In(OTf)3. The results show great promise for In(OTf)3 in synthetic carbohydrate chemistry.
- Giri, Santosh Kumar,Verma, Monika,Kartha, K. P. Ravindranathan
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experimental part
p. 464 - 478
(2009/04/06)
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- Deprotection of acetals and ketals in a colloidal suspension generated by sodium tetrakis(3,5-trifluoromethylphenyl)borate in water
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Deprotection of acetals and ketals can be achieved by using sodium tetrakis(3,5-trifluoromethylphenyl)borate (NaBArF4) as the catalyst in water at 30°C. For example, a quantitative conversion of 2-phenyl-1,3-dioxolane into benzaldehyde was accomplished within five minutes by using this sodium salt (0.1 mol%) in water. Georg Thieme Verlag Stuttgart.
- Chang, Chih-Ching,Liao, Bei-Sih,Liu, Shiuh-Tzung
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p. 283 - 287
(2007/10/03)
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- Nafion-H mediated selective deprotection of terminal isopropylidene acetals and trityl ethers. Application in the synthesis of a substituted piperidone
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A facile chemoselective hydrolysis of terminal isopropylidene acetals has been achieved in good to excellent yields within 2-4 h using Nafion-H in methanol at ambient temperature. This procedure has been employed to synthesize a substituted piperidone der
- Rawal, Girish K.,Rani, Shikha,Kumar, Amit,Vankar, Yashwant D.
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p. 9117 - 9120
(2007/10/03)
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- Mild and chemoselective catalytic deprotection of ketals and acetals using cerium(IV) ammonium nitrate
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Cerium(IV) ammonium nitrate (CAN) is a powerful, though mild, reagent for the efficient and selective removal of a range of ketals and acetals. This novel deprotection method requires only catalytic amounts of CAN and tolerates a variety of functional and protecting groups. Mechanistic insights suggest that the Ce(IV) salts act as unique Lewis acids and not as redox active species.
- Ates, Ali,Gautier, Arnaud,Leroy, Bernard,Plancher, Jean-Marc,Quesnel, Yannick,Vanherck, Jean-Christophe,Markó, István E.
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p. 8989 - 8999
(2007/10/03)
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- Regioselective mono-oxidation of Non-protected carbohydrates by brominolysis of the tin intermediates
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Most of the glycosides examined were smoothly oxidized by the bis-tributyltin oxide-bromine method without protection of the other hydroxyl groups to the mono-oxo derivatives in high yield and with high regioselectivity.The regioselectivity (position of oxidation) can be predicted from two independent rules: anomeric control (the oxidation takes place at C-3 for the glycosides which have an equatorial glycosidic linkage and at C-4 for those which have an axial glycosidic linkage) and axial oxidation for cis-1,2 glycols.Keywords - carbohydrate; glycoside; oxidation; regioselective oxidation; bis-tributyltin oxide-bromine; dibutyltin oxide-bromine; brominolysis; oxo-glycoside; 13C-NMR.
- Tsuda, Yoshisuke,Hanajima, Makiko,Matsuhira, Naohisa,Okuno, Yukihiro,Kanemitsu, Kimihiro
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p. 2344 - 2350
(2007/10/02)
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- ESTERS OF ARYLPROPIONIC ACIDS WITH 1,2:5,6-DI-O-ISOPROPYLIDENE- AND 1,2-O-ISOPROLYLIDENE-α-D-GLUCOFURANOSE
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On fractional crystallization of 3-O-(2-(2-fluoro-4-biphenylyl)propionyl-, 3-O-(2-(4-isobutylphenyl)propionyl)- and 3-O-(2-(6-methoxy-2-naphthyl)propionyl)-1,2:5,6-di-O-isopropylidene-α-D-glucofuranoses V - VII optically pure R-diastereoisomers were isolated.The derivatives of 1,2-O-isopropylidene-α-D-glucofuranose obtained on partial deacetylation of esters V - VII were separated chromatographically to R and S-diastereoisomers.Their hydrolysis or transesterification afforded optically pure arylpropionic acids or their methyl esters, respectively.Kinetic resolutionof the acids gives rise to esters V - VII enriched in R-diastereoisomer.
- Svoboda, Jiri,Capek, Karel,Palecek, Jaroslav
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p. 766 - 774
(2007/10/02)
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- THE SYNTHESIS OF SOME SEVEN-CARBON SUGARS via THE OSMYLATION OF OLEFINIC SUGARS
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The stereochemical outcome of the catalytic osmylation of 6,7-dideoxy-1,2:3,4-di-O-isopropylidene-α-D-galacto-hept-6-enopyranose (10), 5,6-dideoxy-1,2-O-isopropylidene-α-D-xylo-hex-5-enofuranose, (E)- and (Z)-3-O-benzyl-5,6-dideoxy-1,2-O-isopropylidene-α-D-xylo-hept-5-enofuranose (20 and 27, respectively), methyl (Z)-3-O-benzyl-5,6-dideoxy-1,2-O-isopropylidene-α-D-xylo-hept-5-enofuranuronate (26), (E)-3-O-benzyl-5,6-dideoxy-1,2-O-isopropylidene-α-D-ribo-hept-5-enofuranose, benzyl (E)- and (Z)-5,6-dideoxy-2,3-O-isopropylidene-α-D-lyxo-hept-5-enofuranoside (46 and 50, respectively), and methyluronate (49) has been examined.Such oxidations led to satisfactory syntheses of L-glycero-D-gluco-heptose and the corresponding heptitol (from 20), L-glycero-D-gulo-heptitol (from 26), D-glycero-D-gluco-heptitol (from 27), D-glycero-D-galacto-heptitol (from 10 and 46), (meso)-glycero-gulo-heptitol (from 49), and D-glycero-D-manno-heptitol (from 50).
- Brimacombe, John S.,Kabir, Abul K. M. S.
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