- Visible-light-induced acetalization of aldehydes with alcohols
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In this work, we have achieved a simple and general method for acetalization of aldehydes by means of a photochemical reaction under low-energy visible light irradiation. A broad range of aromatic, heteroaromatic, and aliphatic aldehydes have been protected under neutral conditions in good to excellent yields using a catalytic amount of Eosin Y as the photocatalyst. Our visible light mediated acetalization strategies are successful for more challenging acid-sensitive aldehydes and sterically hindered aldehydes. Notably, this protocol is chemoselective to aldehydes, while ketones remain intact.
- Yi, Hong,Niu, Linbin,Wang, Shengchun,Liu, Tianyi,Singh, Atul K.,Lei, Aiwen
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supporting information
p. 122 - 125
(2017/11/27)
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- Acetalization of aldehydes and ketones over H4[SiW 12O40] and H4[SiW12O 40]/SiO2
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H4[SiW12O40] (H-SiW12) is demonstrated to be able to efficiently catalyze the acetalization of aldehydes and ketones with ethylene glycol and 1,3-propanediol. Nevertheless, the possible leaching and the recycling of H-SiW12 are two major disadvantages that largely restrict its further application in industry. Moreover, H 4[SiW12O40] tends to deactivate strong proton sites due to the small surface area of 10 m2 g-1. Due to interactions with surface silanol groups, the proton sites of polyoxometalates (POMs) on SiO2 are less susceptible to deactivation. As such, immobilization of H4[SiW12O40] onto SiO 2 leads to the heterogeneous catalyst H4[SiW 12O40]/SiO2 (H-SiW12/SiO 2), which can catalyze the acetalization of aldehydes and ketones with ethylene glycol and 1,3-propanediol selectively and efficiently without the need of a drying agent. The acetalization process can proceed smoothly at a relatively low temperature under solvent-free conditions. The catalyst of H 4[SiW12O40]/SiO2 can be recycled at least ten times without an obvious decrease in its catalytic activity. As far as we know, the TONs of the H-SiW12/SiO2-catalyzed acetalization of cyclohexanone with ethylene glycol, and benzaldehyde with 1,3-propanediol are the highest reported so far.
- Zhao, Shen,Jia, Yueqing,Song, Yu-Fei
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p. 2618 - 2625
(2014/07/22)
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- Driving an equilibrium acetalization to completion in the presence of water
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Formation of an acetal from a carbonyl substrate by condensation with an alcohol is a classical reversible equilibrium reaction in which the water formed must be removed to drive the reaction to completion. A new method has been developed for acetalization of carbonyl substrates by diols in the presence of water. Complexation of poly(4-styrenesulfonic acid) with poly(4-vinylpyridine) generates a catalytic membrane of polymeric acid at the interface between two parallel laminar flows in a microchannel of a microflow reactor. The catalytic membrane provides a permeable barrier between the organic layer and water-containing layer in the reaction, and permits discharge of water to the outlet of the microreactor to complete the acetalization. Condensation of a variety of carbonyl substrates with diols proceeded in the presence of water in the microflow device to give the corresponding acetals in yields of up to 97% for residence times of 19 to 38 s. the Partner Organisations 2014.
- Minakawa, Maki,Yamada, Yoichi M. A.,Uozumi, Yasuhiro
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p. 36864 - 36867
(2014/11/08)
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- Acetalization of carbonyl compounds catalyzed by bismuth triflate under solvent-free conditions
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Carbonyl compounds were converted to the corresponding 1,3-dioxolanes and 1,3-dioxanes with ethylene glycol and 1,3-propandiol in the presence of bismuth triflate under solvent-free conditions. In addition, high chemoselective protection of aldehydes in the presence of ketones has been achieved.
- Aliyan, Hamid,Fazaeli, Razieh,Massah, Ahmad Reza,Momeni, Ahmad Reza,Naghash, Hamid Javaherian,Moeinifard, Behzad
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experimental part
p. 873 - 876
(2012/04/05)
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- An efficient procedure for protection of carbonyls in Br?nsted acidic ionic liquid [Hmim]BF4
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Protection of carbonyls as acetals or ketals using Br?nsted acidic ionic liquid [Hmim]BF4 as catalyst as well as solvent was investigated. Satisfactory results were obtained for the protection of carbonyls as cycloacetals or ketals with diols. The product can be separated conveniently from the reaction system, and the ionic liquid can be reused after removal of water.
- Wu, Hai-Hong,Yang, Fan,Cui, Peng,Tang, Jie,He, Ming-Yuan
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p. 4963 - 4965
(2007/10/03)
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- An efficient procedure for the preparation of cyclic ketals and thioketals catalyzed by zirconium sulfophenyl phosphonate
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A convenient method for the preparation of cyclic ketals and thioketals using zirconium sulfophenyl phosphonate as catalyst is described.
- Curini,Epifano,Marcotullio,Rosati
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p. 1182 - 1184
(2007/10/03)
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- Selective Catalytic Transesterification, Transthiolesterification, and Protection of Carbonyl Compounds over Natural Kaolinitic Clay
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Transesterification and transthiolesterification of β-keto esters with variety of alcohols and thiols and selective protection of carbonyl functions with various protecting groups catalyzed by natural kaolinitic clay are described. The clay has been found to be an efficient catalyst in transesterifying long chain alcohols, unsaturated alcohols, and phenols to give their corresponding β-keto esters in high yields. For the first time, transthiolesterification of β-keto esters with a variety of thiols has been achieved under catalytic conditions. Clay also catalyzes selective transesterification of β-keto esters by primary alcohols in the presence of secondary and tertiary alcohols giving corresponding β-keto esters. A systematic study involving the reactivity of different nucleophiles (alcohols, amines, and thiols) toward β-keto esters is also described. Sterically hindered carbonyl groups as well as α,β-unsaturated carbonyl groups underwent protection without the deconjugation of the double bond. Chemoselective protection of aldehydes in the presence of ketones has also been achieved over natural kaolinitic clay.
- Ponde, Datta E.,Deshpande, Vishnu H.,Bulbule, Vivek J.,Sudalai, Ammugam,Gajare, Anil S.
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p. 1058 - 1063
(2007/10/03)
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- Preparation of Biologically Active Hydroxyketones and Analogues system through Masked Lithium ω-Enolates Generated by a Naphthalene-catalyzed lithiation
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The reaction of ω-chloroacetal 1 with lithium and a catalytic amount of naphthalene (4 molpercent) in THF at -78 deg C leads to intermediate 3, which by reaction with different electrophiles tCHO, PhCHO, Et2CO, (CH2)5CO, CH3(CH2)nCON(OMe)Me (n = 5, 6)> and final hydrolysis with water affords functionalized acetals 2.Acidic treatment of compounds 2 provides functionalized aldehydes 4.Titanium (IV) mediated chemoselective addition of n-butyllithium to ketoaldehydes 4f,g affords after hydrolysis, hydroksyketones 5f, g.Naphthalene-catalyzed lithiation of chloroacetal 6 followed by reaction with n-butanal yields, after hydrolysis, hydroxyacetal 7, which after transformation into the THP-protected dithiane 9 gives hydroxyketone 10, after successive deprotonation, alkylation and final full deprotection.Hydroxyketones 5g and 10 are interesting natural products. - Key words: hydroxyketones; lithiation; naphthalene; natural products
- Alonso, Emma,Ramon, Diego J.,Yus, Miguel
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- Natural kaolinitic clay: A remarkable reusable solid catalyst for the selective functional protection of aldehydes and ketones
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Natural kaolinitic clay possessing transition metals such as Fe and Ti in its lattice has been found to catalyze efficiently the chemoselective acetalization and thioacetalization of variety of carbonyl compounds with ethane - 1,2 - diol and ethane - 1,2 - dithiol respectively.
- Ponde, Datta,Borate,Sudalai,Ravindranathan,Deshpande
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p. 4605 - 4608
(2007/10/03)
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- BROMINATION OF DIMETHYLACETALS WITH Br2-CHLOROTRIMETHYLSILANE-NaBr
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α-Bromodimethylacetals are obtained in excellent yields by treating dimethylacetals with Br2-NaBr-chlorotrimethylsilane in CH3OH/CH3CN (2:1). The method is suitable for large scale preparation.
- Bellesia, Franco,Boni, Monica,Ghelfi, Franco,Pagnoni, Ugo Maria
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p. 629 - 632
(2007/10/02)
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- Distannoxane-catalyzed acetilization of carbonyls
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1,3-Disubstituted tetrabutyldistannoxanes catalyze acetilization of carbonyl compounds under mild conditions. Thorough investigations of factors influencing this reaction are given. A variety of synthetically useful carbonyl compounds are efficiently converted to acetals. In particular, acetilization of cyclic α,β-unsaturated ketones is readily achieved which have met with only limited success so far.
- Otera, Junzo,Dan-oh, Nobuhisa,Nozaki, Hitosi
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p. 1449 - 1456
(2007/10/02)
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- N-(arylmethyl)-2-(or -4)-cyanopyridinium hexafluoroantimonates as new useful catalysts for acetalization of carbonyl compounds
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Carbonyl compounds 1 were converted to the corresponding 1,3-dioxolanes 2 and 1,3-dioxanes 4 with ethylene glycol and 2,2-dimethyl-1,3-propandiol, respectively, in the presence of 1-3 mol% of N-(benzyl, 4-methylbenzyl or 4-methoxybenzyl)-2(or -4)cyanopyridinium hexafluoroantimonates 3. The catalyst 3d was also effective for the tetrahydropyranylation.
- Lee,Lee,Takata,Endo
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p. 368 - 370
(2007/10/02)
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- Percutaneous absorption enhancers, compositions containing same and method of use
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Novel 1,3-dioxolanes (1,3-dioxyacyclopentanes) are provided along with new 1,3-dioxolanes (1,3-dioxacyclopentanes) compositions which are useful in enhancing the absorption of therapeutic agents through the skin of humans and animals. The method for enhancing skin penetration of therapeutic agents using 1,3-dioxacycloalkanes is also described. The preferred compounds are 1,3-dioxolanes (1,3-dioxacyclopentanes) and 1,3-dioxanes (1,3-dioxacyclohexanes). The preferred compounds have the formula: STR1 wherein R, R0, R1, R2, R3, R4, R5 and R6 are each independently selected from hydrogen and C1 to C18 aliphatic groups, preferably alkyl, alkenyl, and the halo, hydroxy, carboxy, carboxamide and carboalkoxy substituted forms thereof, with at least one of said R's an alkyl or alkenyl group of C4 to C18 and n=0 or 1; the total number of carbon atoms in all of said R groups being no more than 40, and preferably less than 20 and not more than 1 thereof containing 18 or more carbon atoms.
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- Acetals and Ethers. 11. Solubility of Alkyl-Substituted 1,3-Dioxolanes and 1,3-Dioxanes in Water
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2-Alkyl-1,3-dioxolanes, 2-alkyl-4-methyl-1,3-dioxolanes, and 2-alkyl-1,3-dioxanes (alkyl: n-C3H7, ...,n-C6H13) were synthesized and their solubilities in E10-4 M aqueous sodium bicarbonate solution at 293.2 K determined.The standard free energies for transfer from aqueous solution to pure liquid phase, ΔGto, were calculated from the solubility data and the contributions of given fragments of molecules to the free energy estimated.The fve-membered 1,3-dioxolane and six-membered 1,3-dioxane rings given fragments of molecules to the free energy contribution ΔGto, related to the cyclic fragments of the molecules, are +2.84 +/- 0.20 and +2.26 +/- 0.36 kJ mol-1, respectively.Their hydrophilicity is, however, much weaker than hat of the hydroxy group in normal alcohols.The 1,3-dioxolane ring bearing a methyl group at the C-4 atom has a markedly weaker hydrophilic character.
- Sokolowski, Adam,Burczyk, Bogdan,Oles, Jan
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p. 807 - 809
(2007/10/02)
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