- 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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- Nucleophilic reactivity of ethers against terminal epoxides in the presence of BF3: A mechanistic study
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In the presence of BF3, a series of symmetrical and unsymmetrical ethers reacted with epichlorohydrin and 2-[(benzyloxy)methyl] oxirane, two terminal epoxides, to afford 1-alkoxy-3-chloropropan-2-ol and 1-alkoxy-3-(benzyloxy)propan-2-ol. The cleavage of unsymmetrical ethers occurred via an SN2 or SN1 mechanism. Secondary epoxides did not give similar ring-opening products. Copyright
- Kose, Aytekin,Altundas, Ramazan,Secen, Hasan,Kara, Yunus
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p. 1325 - 1330
(2013/08/23)
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- Erbium(III) triflate is a highly efficient catalyst for the synthesis of β-alkoxy alcohols, 1,2-diols and β-hydroxy sulfides by ring opening of epoxides
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Chemo- and stereoselectivity in the ring-opening reaction of epoxides with erbium(III) triflate are described. Epoxides can be cleaved under neutral conditions with alcohols and thiols in the presence of catalytic amounts of Lewis acid, affording the corresponding β-alkoxy alcohols and β-hydroxy sulfides in high yields. In water, epoxide ring opening occurs to produce the corresponding diols in good yields.
- Dalpozzo, Renato,Nardi, Monica,Oliverio, Manuela,Paonessa, Rosina,Procopio, Antonio
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experimental part
p. 3433 - 3438
(2010/02/28)
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- Highly efficient cleavage of epoxides catalyzed by B(C6F5)3
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A highly effective protocol for ring opening of epoxides with allyl and propargyl alcohols, aniline and thiophenol in the presence of catalytic amounts of B(C6F5)3 has been developed. Benzyl, tetrahydropyranyl, tert-butyld
- Chandrasekhar,Raji Reddy,Nagendra Babu,Chandrashekar
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p. 3801 - 3803
(2007/10/03)
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- Original synthesis of linear, branched and cyclic oligoglycerol standards
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A variety of authentic standards of linear, branched and cyclic oligomers of glycerol, with well-defined structures and degrees of polymerisation from 2 to 5, have been efficiently synthesised. Linear oligomers were obtained by means of a convergent approach based on regioselective opening of bis(epoxides) with solketal; branched compounds were synthesised using oxidative cleavage of the corresponding anhydrohexitols as the key step. A 6-exo-trig halocyclisation reaction involving heteroatom-tethered unsaturated alcohols permitted an efficient synthesis of the precursors of selected cyclic dimers; larger cyclic oligomers were prepared by two one-pot Williamson reactions using a ditriflate derived from diglycerol. All these methodologies permitted further scaling up.
- Cassel, Stephanie,Debaig, Catherine,Benvegnu, Thierry,Chaimbault, Patrick,Lafosse, Michel,Plusquellec, Daniel,Rollin, Patrick
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p. 875 - 896
(2007/10/03)
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- The reaction between epichlorohydrin and polysaccharides: Part 2, synthesis of some model substances, with cyclic substituents
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Eight derivatives of methyl α-D-glucopyranoside, in which the substituents are part of cyclic structures, have been prepared as model substances for possible structural elements formed on reaction of polysaccharides with epichlorohydrin.The substances were converted into the permethylated alditol-1-d acetates and characterised by CIMS and EIMS. Keywords: Cross-linked polysaccharides; Epichlorohydrin
- Holmberg, Lars,Lindberg, Bengt,Lindqvist, Bengt
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