- 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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- Acid-free, organocatalytic acetalization
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The acid-free, organocatalytic acetalization of various aldehydes and ketones with N,N′-bis[3,5-bis(trifluoromethyl)phenyl]thiourea is presented. The neutral, double hydrogen bonding thiourea catalyst can be used at very low loadings of 0.01-1 mol% at room temperature to furnish the respective acetals in 65-99% yield at turnover frequencies around 600 h-1. Acid-labile TBDMS-protected as well as unsaturated aldehydes can be converted efficiently into their acetals utilizing this very mild and highly practical method.
- Kotke, Mike,Schreiner, Peter R.
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p. 434 - 439
(2007/10/03)
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- Process for producing alicyclic aldehydes
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In the production of an alicyclic aldehyde, a starting aromatic aldehyde is converted into an aromatic acetal for protecting the formyl group. The aromatic ring of the aromatic acetal is then hydrogenated to convert the aromatic acetal into an alicyclic acetal, which is then hydrolyzed to cleave the acetal protecting group to obtain the aimed alicyclic aldehyde.
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Page/Page column 4-5
(2008/06/13)
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- Highly shape-selective, biomimetic, and efficient deprotection of carbonyl compounds masked as ethylene acetals or dioxolanes produced from 1,2-ethanediol
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A simple, mild, efficient, and organic solvent-free biochemical approach for the deprotection of carbonyl compounds protected as 1,3-dioxolanes through the use of cyclodextrins as catalysts has been developed. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Ji, Hong-Bing
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p. 3659 - 3662
(2007/10/03)
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- Acetonyltriphenylphosphonium bromide and its polymer-supported analogues as catalysts for the protection of carbonyl compounds as acetals or thioacetals
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Both acetonyltriphenylphosphonium bromide (ATPB) and poly-p-styryldiphenylacetonylphosphonium bromide (PATPB) are excellent catalysts in the protection of aldehydes as acetals or thioacetals. In general, ATPB is highly selective as ketones do not give good yields of ketals with this catalyst.
- Hon, Yung-Son,Lee, Chia-Fu,Chen, Rong-Jiunn,Huang, Yi-Fen
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p. 2829 - 2842
(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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- AN EFFICIENT SbCl3-METAL SYSTEM FOR ALLYLATION, REDUCTION AND ACETALIZATION OF ALDEHYDES
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SbCl3-Fe or SbCl3-Al could induce allylation of aldehydes with allylic halides at room temperature to give high yields of the corresponding homoallylic alcohols with high regio- and chemoselectivity.SbCl3-Al or SbCl3-Zn in DMF-H2O was found to be an efficient reduction system for conversion of aldehydes to alcohols at room temperature in excellent yields.While alcohol was used as solvent instead of DMF-H2O, the acetalization product was obtained in almost quantitative yield.Catalytic amount of SbCl3 was effective for this purpose.This acetalization method could also be applied to ketone.
- Wang, Wei-Bo,Shi, Li-Lan,Huang, Yao-Zeng
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p. 3315 - 3320
(2007/10/02)
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- SILICON IN SYTHESIS-17 CHLROMETHYL(TRIMETHYLSILYL)LITHIUM-A NEW REAGENT FOR THE DIRECT CONVERSION OF ALDEHYDES AND KETONES INTO α,β-EPOXYTRIMETHYLSILANES
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Treatment of chloromethyltrimethylsilane 1 with sec-BuLi at -78 deg produces chloromethyl(trimethylsilyl)lithium 4.Treatment of 4 with a wide range of aldehydes and ketones gives α,β-epoxytrimethylsilanes 5-28, which on acidic hydrolysis give homologated aldehydes.
- Burford, Clifford,Cooke, Frank,Roy, Glenn,Magnus, Philip
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p. 867 - 876
(2007/10/02)
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