- Dehydrative Glycosylation Enabled by a Comproportionation Reaction of 2-Aryl-1,3-dithiane 1-Oxide?
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A new dehydrative glycosylation reaction has been established by capitalizing on the comproportionation reaction of 2-aryl-1,3-dithiane 1-oxides promoted by triflic anhydride (Tf2O). By wedding the high potency of thiophilic promoter system with the step efficiency of dehydrative glycosylation, this reagent underwent facile intermolecular oxothio acetalization with C1-hemiacetal donor to install a temporary leaving group, rendering a transient electrophilic center at the remote site to the anomeric position. The sulfenyl triflate tethered at the terminus concomitantly activated the sulfide intramolecularly to afford the oxocarbenium ion, thereby facilitating the title glycosylation. Aside from accommodating broad range functional groups and inactive hemiacetal substrates, the present activation protocol also proved expedient for 1,3-diol protection. Most importantly, this method further provided a fresh perspective for the application of sulfur chemistry to carbohydrate chemistry.
- Cai, Lei,Zeng, Jing,Li, Ting,Xiao, Ying,Ma, Xiang,Xiao, Xiong,Zhang, Qin,Meng, Lingkui,Wan, Qian
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supporting information
p. 43 - 49
(2019/11/28)
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- Cosmetic/sunscreen compositions containing dibenzoylmethane compounds and dithiolane compound photostabilizers therefor
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Cosmetic/sunscreen compositions contain a combination of at least one dibenzoylmethane sunscreen compound and a photostabilizing amount of at least one dithiolane compound of formula (I) below:
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- Depigmenting keratin materials utilizing dithiolane compounds
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A cosmetic regime or regimen for depigmenting, lightening and/or bleaching keratin materials, especially the skin, entails topically applying thereon a cosmetic composition containing a dithiolane compound of formula (I): in which: Y is O, NR1 or SR1 is a hydrogen atom; a C1-C20 alkyl radical or an optionally substituted phenyl radical;R is a hydrogen atom; or a C1-C20 alkyl radical, or an optionally substituted phenyl radical, or a C1-C8 alkyl radical containing an optionally substituted phenyl substituent;n=0 or 1 or 2; and also the salts, chelates, solvates and optical isomers thereof.
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- A new approach to the reduction of sulfoxides to sulfides with 1,3-dithiane in the presence of electrophilic bromine as catalyst
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A new, mild, and novel method is described for the efficient deoxygenation of sulfoxides to their corresponding sulfides with 1,3-dithiane at room temperature in the presence of catalytic amounts of N-bromosuccinimide (NBS), 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TABCO), or Br2 as the source of electrophilic bromine.
- Iranpoor, Nasser,Firouzabadi, Habib,Shaterian, Hamid Reza
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p. 2826 - 2830
(2007/10/03)
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- Efficient hydrolysis of dithioacetals by the N-fluoro-2,4,6-trimethylpyridinium triflate-water system
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Dithioacetals including 1,3-dithianes and 1,3-dithiolanes are efficiently cleaved by the title reagent system to the parent carbonyl compounds. The cleavage of diprotected symmetrical α-diketones and p-phenylenediketones gives monoketones in good yields. Amide, 1,3-dioxolane, disulfide, ester, ether, hydroxy, nitrile, nitro, and sulfide functions are relatively stable under the cleavage conditions but thiols are oxidized to disulfides.
- Kiselyov,Strekowski,Semenov
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p. 2151 - 2158
(2007/10/02)
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- Degenerate intermolecular thiolate-disulfide interchange involving cyclic five-membered disulfides is faster by ~103 than that involving six- or seven-membered disulfides
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The rate constants for degenerate intermolecular thiolate-disulfide interchange involving 1,2-dithiolane (S(CH2)3S) are higher than those involving 1,2-dithiane (S(CH2)4S) by a factor of ~650 in mixtures of DMSO-d6 and D2O. The extrapolated rate constant for 1,2-dithiolane in DMSO-d6 is fast (k ~ 108 M-1 s-1). The rate constants for cyclic six- and seven-membered disulfides are similar to those for acyclic disulfides. Rate constants for self-exchange were measured by dynamic 1H NMR line-shape analysis. The evolutionary selection of lipoamide as the cofactor in 2-oxo acid dehydrogenases may reflect the fast rate of ring opening of the dithiolane ring by nucleophiles.
- Singh, Rajeeva,Whitesides, George M.
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p. 6304 - 6309
(2007/10/02)
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- A Convenient and Mild Dethioacetalization Method Using Fe(bpy)3(ClO4)3*3H2O
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Reactions of 1,3-dithianes, 1,3-dithiolanes, and benzenethioacetals with tris(2,2'-bipyridyl)iron(III) perchlorate, Fe(bpy)3(ClO4)3*3H2O, gave the parent carbonyl compounds in high yields, immediately.These reactions may proceed by one-electron abstraction from the sulfur atom of acetals by the iron(III) complex, and they provide a new convenient and mild dethioacetalization method.Keywords - dethioacetalization; 1,3-dithiane; 1,3-dithiolane; benzenethioacetal; tris(2,2'-bipyridyl)iron(III) perchlorate; one-elcetron abstraction
- Murase, Masayuki,Kotani, Eiichi,Tobinaga, Seisho
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p. 3595 - 3598
(2007/10/02)
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- ANODIC OXIDATION OF DIALKYL AND DIARYL DITHIOACETALS
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The mechanism of the anodic oxidation of dithioacetals is discussed, taking into account new results concerning both mixed electrolyses and oxidations in super-dried solvents.In the case of the oxidation of aryldithioacetals, the formation of the -S-S- linkage is involved with a bond cleavage followed by a dimerisation.On the other hand, in the case of aliphatic starting materials the mechanism looks more consistent with the existence of a dicationic intermediate which is scavenged by nucleophiles.
- Gourcy, Jean,Martigny, Patrick,Simonet, Jacques,Jeminet, Georges
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p. 1495 - 1502
(2007/10/02)
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- AN EFFECTIVE AND MILD ELECTROCATALYTIC PROCEDURE FOR THE REMOVAL OF 1,3-DITHIANE PROTECTING GROUPS
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The 1,3-dithiane protecting group can effectively be removed by indirect electrochemical oxidation under extremely mild conditions, if catalytic amounts of tris(p-tolyl) amine are used as homogeneous electron transfer agents.
- Platen, Martin,Steckhan, Eberhard
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p. 511 - 514
(2007/10/02)
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