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Aldehydes and Glyoxals

The rather labile Schiff base interaction can be chemically stabilized by reduction. The addition of sodium borohydride or sodium cyanoborohydride to a reaction medium containing an aldehyde compound and an amine-containing molecule will result in reduction of the Schiff [Pg.173]

Although both borohydride and cyanoborohydride have been used for reductive amination purposes, borohydride will reduce the reactive aldehyde groups to hydroxyls at the same time it converts any Schiff bases present to secondary amines. [Pg.141]


Periodic acid oxidation will also act on a-hydroxy aldehydes and ketones, a-diketones, a-keto aldehydes, and glyoxal. If the two neighboring hydroxyl groups are on an aromatic ring, the carbon-carbon bond is not cleave but the reactant is still oxidized. Thus, catechol is oxidized to the corresponding quinone. [Pg.438]

Dioxane under these conditions forms a mixture of ethylene glycol, glycolic aldehyde, and glyoxal, isolated as 2,4-dinitrophenylhydrazones (79AJC2787). [Pg.55]

An aqueous solution of fuchsin (/7-rosaniline hydrochloride) decolorized with sodium hydrogen sulfite or with sodium sulfite becomes red-violet to blue if aldehydes are added to it. The reappearance of this color is not caused by simple oxidation to fuchsin, but represents a specific reaction of the aldehydic group —CHO. However, unsaturated aldehydes and certain aromatic aldehydes (vanillin, p-aminobenzaldehyde, p-dimethylaminobenz-aldehyde) and glyoxal do not react. According to more recent views (15), both amino groups of the fuchsinleukosulfonic acid (VI) react with the... [Pg.217]

Carbon—nitrogen double bonds in imines, hydrazones, oximes, nitrones, azines, and substituted diazomethanes can be cleaved, yielding mainly ketones, aldehydes and/or carboxyHc acids. Ozonation of acetylene gives primarily glyoxal. With substituted compounds, carboxyHc acids and dicarbonyl compounds are obtained for instance, stearoHc acid yields mainly azelaic acid, and a smaH amount of 9,10-diketostearic acid. [Pg.493]

A variation involves the reaction of benzylamines with glyoxal hemiacetal (168). Cyclization of the intermediate (35) with sulfuric acid produces the same isoquinoline as that obtained from the Schiff base derived from an aromatic aldehyde and aminoacetal. This method has proved especially useful for the synthesis of 1-substituted isoquinolines. [Pg.397]

Aromatic aldehydes 1 can undergo a condensation reaction to form a-hydroxy ketones 2 (also called benzoins) upon treatment with cyanide anions.This reaction, which is called benzoin condensation, works by that particular procedure with certain aromatic aldehydes and with glyoxals (RCOCHO). [Pg.37]

Preparation of the key tropine is achieved by any one of several variations on the method first developed by Robinson, which involves reaction of a primary amine with dihydroxyacetone and glyoxal. Reduction of the carbonyl group in the product (86) followed by acylation affords the aminoester (88). Transesterification with ester aldehyde 89... [Pg.160]

The coupling of enals and glyoxals was realized by hydrogen-mediated reaction with the cationic Rh complex and PI13P [35]. The intermediate aldehyde enolates derived via Rh-catalyzed hydrogenation were trapped with glyoxals to form (l-hydroxy-y-kclo-aldchydes, which were treated sequentially with hydrazine to give pyridazines in a one-pot transformation to provide, for example, a 62% yield of 72 (Scheme 21). [Pg.127]

Nature has designed the active sites in the enzymes GO and glyoxal oxidase in order to perform a hydrogen-atom abstraction reaction from the a-carbon atom of an O-bound alcoholate (or aldehyde) in the rds. The essence of this chemistry is depicted in Fig. 8. [Pg.198]

The extent of oxidation, when determined by the reaction of the product with phenylhydrazine, is 85%. Hydrolysis of the oxidized xylan should produce approximately equimolar quantities of D-glyceraldehyde and glyoxal. Experimental determination of glyceraldehyde indicates 67 % of the theoretical when the oxidized xylan is distilled with sulfuric acid and the evolved methylglyoxal measured as the phenylosazone. Glyoxal is isolated in 63% yield, when separated as the phenylosazone or as the dioxime. Aldehyde groups in the oxidized xylan may be further... [Pg.297]

Carnosine may help suppress some features of aging at cellular and whole organism levels, possibly by inhibiting the reactivity of ROS and deleterious aldehydes including formation of AGEs (Hipkiss et ah, 2002). It is theoretically possible that the dipeptide is beneficial towards those conditions where formation of protein AGEs plays important and most likely causal roles. Even in complication-free diabetics, the levels AGE precursors such as MG and glyoxal are elevated in their sera (Han et ah,... [Pg.111]

For preparative purposes, the reaction of thiocarbonyl ylides with carbonyl compounds can be considered as an alternative method for the synthesis of 1,3-oxathiolanes. Aromatic aldehydes, chloral, glyoxalates, mesoxalates, pyruvates as well as their 3,3,3-trifluoro analogues are good intercepting reagents for thioketone (5)-methylides (36,111,130,163). All of these [3 + 2] cycloadditions occur in a regioselective manner to produce products of type 123 and 124. [Pg.342]

The reaction of indolizines with aldehydes and ketones in the presence of acids yields coloured salts, two of which (43 and 44) are given here for illustration. The salts (45) and (46) have been obtained from the reaction of the pertinent indolizines with formaldehyde and glyoxal respectively. Polymethine dyes, some of which have found application in photography, have been prepared from indolizines and malondialdehyde derivatives or vinylogous dialdehydes (47) was prepared from 1,2-dimethylindolizine and /3-ethoxy-acrolein diethyl acetal (48). [Pg.456]

Lower sugars, a-hydroxy-aldehydes and -ketones and glyoxal undergo similar reactions to yield furans which are unsubstituted at position 3 (57CR(244)1047),... [Pg.685]

The proposed reaction mechanism for the destruction of aqueous solutions of TCE or PCE predicts the formation of stable oxidized polar organic compounds. These compounds consist of acids, aldehydes, and possibly halo-acetic acids. Three possible mechanisms have been proposed for the formation of by-products due to the irradiation of aqueous solutions containing TCE and PCE. The first is for the formation of formaldehyde, acetaldehyde, and glyoxal, which are formed at a concentration of approximately two orders of magnitude less than the influent solute concentration. Second, the formation of formic acid decreased with increasing radiation dose. The formic acid concentration was found to be higher for PCE than TCE. These results are most probably due to the slower reaction rate constants of PCE with e and OH, compared to TCE. The third possible reaction is the formation of haloacetic acids when TCE and OH react. The mechanism of decomposition of PCE by OH is shown in Equation (12.30) to Equation... [Pg.485]

Antecedent dehydration reactions can be complicated by acid-base reactions, for different protonated forms show different rates of dehydration. In all the systems studied so far — pyridine aldehydes (77, 78—80) quinazoline 81, 82) and glyoxalic acid (83) — either the dehydration of the conjugate base is faster than that of the conjugate acid, or the conjugate base is less hydrated. This is shown by the increase of current at pH > 2 in Fig. 22. The increase of current in acidic media corresponds... [Pg.38]

The enantioselective addition of allylstannanes to glyoxylates and glyoxals, and also simple aromatic and aliphatic aldehydes, catalysed by chiral (salen)Cr(III) complexes, has been studied.133 The reaction proceeded smoothly for the reactive 2-oxoaldehydes and allyltributy 1 tin in the presence of small amounts (1-2 mol%) of (salen)Cr(III)BF4 under mild, undemanding conditions. The stereochemical results have been rationalized on the basis of the proposed model. [Pg.298]


See other pages where Aldehydes and Glyoxals is mentioned: [Pg.173]    [Pg.161]    [Pg.234]    [Pg.141]    [Pg.15]    [Pg.15]    [Pg.384]    [Pg.173]    [Pg.161]    [Pg.234]    [Pg.141]    [Pg.15]    [Pg.15]    [Pg.384]    [Pg.209]    [Pg.311]    [Pg.17]    [Pg.131]    [Pg.159]    [Pg.120]    [Pg.173]    [Pg.95]    [Pg.112]    [Pg.152]    [Pg.1209]    [Pg.80]    [Pg.340]    [Pg.422]    [Pg.94]    [Pg.209]    [Pg.311]    [Pg.161]    [Pg.515]    [Pg.489]    [Pg.98]   


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Aldehydes glyoxal

Glyoxalate

Glyoxalic

Glyoxals

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