- Regioselective mono and multiple alkylation of diols and polyols catalyzed by organotin and its applications on the synthesis of value-added carbohydrate intermediates
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A catalytic amount of dibutyltin dichloride was used to develop regioselective alkylation of diols and multiple alkylation of polyols. Alkyl groups, including allyl, alkynyl and long-chain alkyl groups, were successfully introduced to one or two hydroxyl
- Xu, Hengfu,Ren, Bo,Zhao, Wei,Xin, Xiaoting,Lu, Yuchao,Pei, Yuxin,Dong, Hai,Pei, Zhichao
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- Regio/site-selective alkylation of substrates containing a: Cis -, 1,2- or 1,3-diol with ferric chloride and dipivaloylmethane as the catalytic system
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In this study, we reported the regio/site-selective alkylation of substrates containing a cis-, 1,2- or 1,3-diol with FeCl3 as a key catalyst. A catalytic system consisting of FeCl3 (0.01-0.1 equiv.) and dipivaloylmethane (FeCl3/dipivaloylmethane = 1/2) was used to catalyze the alkylation in the presence of a base. The produced selectivities and isolated yields were similar to those obtained by methods using the same amount of FeL3 (L = acylacetone ligand) as the catalyst in most cases. The previously reported FeL3 catalysts for alkylation are not commercially available and have to be synthesized prior to use. In contrast, FeCl3 and dipivaloylmethane (Hdipm) are very common and inexpensive nontoxic reagents in the lab, thereby making the method much greener and easier to handle. Mechanism studies confirmed for the first time that FeCl3 initially reacts with two equivalents of Hdipm to form [Fe(dipm)3] in the presence of a base in acetonitrile, followed by the formation of a five or six-membered ring intermediate between [Fe(dipm)3] and two hydroxyl groups of the substrate. A subsequent reaction between the cyclic intermediate and the alkylating agent results in selective alkylation of the substrate.
- Lv, Jian,Liu, Yu,Zhu, Jia-Jia,Zou, Dapeng,Dong, Hai
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supporting information
p. 1139 - 1144
(2020/03/11)
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- An Iron(III) Catalyst with Unusually Broad Substrate Scope in Regioselective Alkylation of Diols and Polyols
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In this study, [Fe(dibm)3] (dibm=diisobutyrylmethane) is shown to have unusually broad scope as a catalyst for the selective monoalkylation of a diverse set of 1,2- and 1,3-diol-containing structures. The mechanism is proposed to proceed via a cyclic dioxolane-type intermediate, formed between the iron(III) species and two adjacent hydroxyl groups. This approach represents the first transition-metal catalysts that are able to replace stoichiometric amounts of organotin reagents in regioselective alkylation. The reactions generally lead to very high regioselectivities and high yields, on par with, or better than, previous methods used for regioselective alkylation.
- Ren, Bo,Ramstr?m, Olof,Zhang, Qiang,Ge, Jiantao,Dong, Hai
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p. 2481 - 2486
(2016/02/12)
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- Dimethyltin Dichloride Catalyzed Regioselective Alkylation of cis-1,2-Diols at Room Temperature
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Here, we have developed a mild and general method for the regioselective installation of benzyl, allyl, para-methoxybenzyl and naphthyl groups on cis-1,2-diols. The optimized method operates at room temperature using dimethyltin dichloride as catalyst and
- Saikam, Varma,Dara, Saidulu,Yadav, Mahipal,Singh, Parvinder Pal,Vishwakarma, Ram A.
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p. 11916 - 11925
(2016/01/09)
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- Tin-mediated regioselective benzylation and allylation of polyols: Applicability of a catalytic approach under solvent-free conditions
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The first catalytic version of the stannylene-mediated benzylation and allylation of polyols is reported. The methodology is based on a simple solvent-free protocol that significantly advances, in terms of both experimental ease and synthetic scope, the a
- Giordano, Maddalena,Iadonisi, Alfonso
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p. 213 - 222
(2014/01/17)
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- Facile synthesis of the heptasaccharide repeating unit of O-deacetylated GXM of C. neoformans serotype B
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A heptasaccharide, β-d-Xylp-(1→2)-α-d-Manp-(1→3)- [β-d-Xylp-(1→2)]-α-d-Manp-(1→3)-[β-d-GlcpA-(1→2)] [β-d-Xylp-(1→4)]-α-d-Manp, the repeating unit of the exopolysaccharide from Cryptococcus neoformans serovar B, was synthesized as its methyl glycoside. Thu
- Zhao, Wei,Kong, Fanzuo
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p. 121 - 130
(2007/10/03)
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- Analysis of the binding specificities of oligomannoside-binding proteins using methylated monosaccharides
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The binding specificities of the closely related lectins from Canavalia ensiformis and Dioclea grandiflora were examined using specifically O-alkylated mono- and disaccharides. Both lectins accept any substitution at the monosaccharide C2 hydroxyl group. The binding energy of C2-alkylated ligands-concanavalin A complexes increases by 1 kcal mol-1 for the C2-O-ethyl ligand, while the binding energies of the corresponding complexes with the Dioclea lectin are identical. Both lectins accept methyl, but not ethyl, substitution of the C3 hydroxyl, in contrast to earlier reports. The results are interpreted in terms of existing models of the concanavalin A binding site. While the results are consistent with a model of the concanavalin A extended binding site that places the non-reducing terminus of all disaccharides in the monosaccharide binding site, they point to the dangers of interpreting the binding behavior of unnatural saccharide ligands on the basis of crystallographic data obtained with native ligands.
- Chervenak, Mary C.,Toone, Eric J.
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p. 1963 - 1977
(2007/10/03)
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- SYNTHETIC STUDIES ON NOGALAMYCIN: STEREOSPECIFIC C-5 ALKYLATION OF A SUGAR DERIVATIVE VIA CLAISEN REARRANGEMENT AND A NEW ROUTE TO 1,1,4-TRIALKOXYBUTA-1,3-DIENES.
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Claisen rearrangement of the 4-methoxybutadienylether of the allylic alcohol 13 which was made in 15 steps from D-glucose, afforded one major aldehyde 17 or 18 in good yield.All attempts to oxidize to an acid were unsuccessful.The model compound 24 and compound 13, were converted respectively to the α, β-unsaturated esters 25 and 26.Compound 25 was further transformed into 1,1,4-trialkoxybuta-1,3-diene 27 which was found unreactive towards quinones.
- Vatele, J.-M.
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p. 4443 - 4450
(2007/10/02)
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