1,2-ethanediol aldehydes

The most commonly used protected derivatives of aldehydes and ketones are 1,3-dioxolanes and 1,3-oxathiolanes. They are obtained from the carbonyl compounds and 1,2-ethanediol or 2-mercaptoethanol, respectively, in aprotic solvents and in the presence of catalysts, e.g. BF, (L.F. Fieser, 1954 G.E. Wilson, Jr., 1968), and water scavengers, e.g. orthoesters (P. Doyle. 1965). Acid-catalyzed exchange dioxolanation with dioxolanes of low boiling ketones, e.g. acetone, which are distilled during the reaction, can also be applied (H. J. Dauben, Jr., 1954). Selective monoketalization of diketones is often used with good success (C. Mercier, 1973). Even from diketones with two keto groups of very similar reactivity monoketals may be obtained by repeated acid-catalyzed equilibration (W.S. Johnson, 1962 A.G. Hortmann, 1969). Most aldehydes are easily converted into acetals. The ketalization of ketones is more difficult for sterical reasons and often requires long reaction times at elevated temperatures. a, -Unsaturated ketones react more slowly than saturated ketones. 2-Mercaptoethanol is more reactive than 1,2-ethanediol (J. Romo, 1951 C. Djerassi, 1952 G.E. Wilson, Jr., 1968). 

Diols that bear two hydroxyl groups m a 1 2 or 1 3 relationship to each other yield cyclic acetals on reaction with either aldehydes or ketones The five membered cyclic acetals derived from ethylene glycol (12 ethanediol) are the most commonly encoun tered examples Often the position of equilibrium is made more favorable by removing the water formed m the reaction by azeotropic distillation with benzene or toluene... 

The addition of doubly deprotonated HYTRA to achiral4 5 as well as to enantiomerically pure aldehydes enables one to obtain non-racemic (3-hydroxycarboxylic acids. Thus, the method provides a practical solution for the stereoselective aldoi addition of a-unsubstituted enolates, a long-standing synthetic problem.7 As opposed to some other chiral acetate reagents,7 both enantiomers of HYTRA are readily available. Furthermore, the chiral auxiliary reagent, 1,1,2-triphenyl-1,2-ethanediol, can be recovered easily. Aldol additions of HYTRA have been used in syntheses of natural products and biological active compounds, and some of those applications are given in Table I. (The chiral center, introduced by a stereoselective aldol addition with HYTRA, is marked by an asterisk.)... 

Synonyms AI3-18303 2-Butenal CCRIS 909 Crotenaldehyde Crotonal Crotonic aldehyde EINECS 224-030-0 1,2-Ethanediol dipropanoate Ethylene glycol dipropionate Ethylene dipropionate Ethylene propionate p-Methylacrolein NC1-C56279 NSC 56354 Propylene aldehyde RCRA waste number U053 Topanel UN 1143. 

Ethanediol (ethylene glycol) [5g] Commercial products are pure enough for most purposes. In order to remove water of 2000 ppm, the ethanediol is dehydrated with sodium sulfate anhydride and distilled twice at reduced pressure in a dry nitrogen atmosphere in order to avoid oxidation to aldehyde. 

P-Hydroxy carboxylic acids (12,3).2 This acetate on double deprotonation with LDA undergoes diastereoselective aldol reactions with aldehydes. The adducts are easily hydrolyzed to optically active P-hydroxycarboxylic acids with release of (R)-(+)-1,1,2-triphenyl-1,2-ethanediol, the precursor to 1. Optically pure acids can be obtained by crystallization of the salt with an optically active amine such as (S)-(—)-1 -pheny lethylamine. 

Aldehydes and ketones are usually protected by converting them to acetals by reaction with an alcohol in the presence of acid (see Section 18.9). Although many different alcohols could be used, ethylene glycol (1,2-ethanediol) or 1,3-propanediol is most often... 

Periodic acid is a versatile oxidant since, depending on pH, the redox potential for the periodate-iodate couple varies from 0.7 V in aqueous basic media to 1.6 V in aqueous acidic media.Based on this observation, Villemin and Ricard devised an oxidative cleavage of glycols, in which mcjo-l,2-diphenyl-1,2-ethanediol was oxidized by periodic acid on alumina to benzaldehyde in 82% yield in aqueous ethanol (90% ethanol) at room temperature in 26 h. The same supported oxidant converted aromatics into quinones. In the presence of transition metal complexes (Mn ), a-arylalkenes suffer oxidative cleavage to aldehydes. For example, tran.r-stilbene gives benzaldehyde at room temperature. 

SYNS ALDEHYDE CROTONIQUE (FRENCH) trans-2-BUTENAL (E)-2-BUTENAL CROTONAL CROTONALDEHYDE CROTONIC ALDEHYDE 1,2-ETHANEDIOL DIPROPANOATE (9C1) ETHYLENE GLYCOL DIPROPIONATE (SCI) ETHYLENE PROPIONATE p-METHYL ACROLEIN NCI-C56279 PROPYLENE ALDEHYDE RCR.Y WASTE NUMBER U053 TOPANEL... 

Bis(o-nitrophenyl)ethanediol (50) has been proposed as a practical photolabile protecting group for ketones and aldehydes which is superior to the monosub-stituted o-nitrophenylethanediol. The presence of a single stereocentre in the latter leads to the formation of two diastereomers when it is used with another chiral molecule, thus complicating NMR signal patterns, and often making purification difficult. In addition, the obvious alternative of ketal formation from two molecules of o-nitrobenzyl alcohol instead of a diol is usually impractical. On the other hand (50) is easily accessible as a pure enantiomer, and the ketals which it forms with aldehydes and ketones are smoothly deprotected in neutral conditions by irradiation at 350 nm. 

R)-(+)-1,1,2-TriphenyM, 2-ethanediol is available from methyl3 and ethyl4 (R)-(-)-mandelate by treatment with phenylmagnesium bromide. The synthesis of (R)-(+)-2-hydroxy-1,2,2-triphenylethyl acetate [(R)-HVTRA] has been reported previously by the submitters.5 6 (S)-(-)-2-Hydroxy-1,2,2-triphenylethyl acetate is available according to this procedure starting from the enantiomeric methyl (S)-(+)-mandelate or (S)-(+)-mandelic acid, respectively, both of which are commercially available. Doubly deprotonated HYTRA can be used to introduce an acetate moiety into achiral as well as chiral aldehydes in an enantioselective manner. 

Formation of spiro orthoesters such as 4 is achieved in high yield by reaction of cyclic ketene monothioacetals such as 3 with ethanediol and camphorsulfonic acid <04SL2013>. A variety of substituted epoxy ketones 5 rearrange to the benzodioxoles 6 upon treatment with Bu.,N CN in CHjClj or K1 in acetone <04T3825>. Condensation of phenacyl carbonates 7 with aromatic aldehydes in the presence of MgCClO ), 2,2 -bipyridyl, A-methylmorpholine and molecular sieves gives the trans dioxolanones 8 <04SL1195>. 

It is true that, for instance, one does not find under the keyword aldehyde the preparation of benzaldehyde (a) from toluene by way of benzyl chloride or benzaldehyde dichloride, (b) from benzene and hydrogen cyanide-hydrogen chloride (Gattermann-Koch) or from bromobenzene by way of phenyl-magnesium bromide and formic ester (Grignard), and (c) from stilbene and ozone or from 1,2-diphenyl-1,2-ethanediol and lead tetraacetate but such a collection of syntheses is to be found in the systematic textbooks and reference works of organic chemistry, and the compass of the large reactions remains nevertheless substantially intact in our treatment. 

A look at several examples is instructive. Stefan and Bolton (1998) determined that advanced oxidation of 1,4-dioxane leads to the transformation products of mono- and di-formate esters of 1,2-ethanediol, various organic acids (e.g., formic, acetic, glycohc, and oxaUc acids), and aldehydes (e.g.. 

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