Acetaldehydes derivatives

Acenaphtheno[l,2-e][l,2,4]triazolo[4,3-h][l,2,4]triazine 747 was prepared (79AP147) by cyclizing 3-hydrazinoacenaphtheno[l,2-e][l,2,4]tria-zine 746 with formic acid. Reaction of 746 with sugars gave the hydrazones, which cyclized with iron(III) chloride to give 748 (93BCJ00). Similarly, the acetaldehyde derivative of 746 was cyclized to 748. The structure of 748 (R = Me) rather than 747 (R = Me) was deduced by unequivocal synthesis of the latter by condensation of acenaphthenequinone with 3,4-diamino[l,2,4]triazole (Scheme 155). 

From the mechanism given in problem 7-8 for the decomposition of acetaldehyde, derive a rate law or set of independent rate laws, as appropriate, if H2 and C2Hs are major products (in addition to CH4 and CO). 

The second category of aldehyde dehydrogenases are efficient catalysts of the oxidation of both aryl and alkyl aldehydes to the corresponding carboxylic acids. The most well known and common of such reactions is the oxidation of acetaldehyde, derived from alcohol, to acetic acid. 

The reaction of diethyl aminomethylenemalonate (13) with acetaldehyde derivatives in xylene in the presence of p-toluenesulfonic acid afforded 3-azapentadienes (1557) (70AP612). 

This technique may also be modified to prepare acetaldehyde derivatives by use of 2,4,4,6-tetramethyl-5,6-dihydro-l,3(4H)-oxazine1 2 3 4 5 6 7 and 2-carboethoxy acetaldehydes using 2-(carbo-ethoxymethyl)-4,4,6-trimethyl-5,6-dihydro-l,3(4H)-oxazine.3 Functionalized aldehydes and dialdehydes may also be obtained by suitable modification.8 Generally, the intermediates can be used without purification and the overall yields of the aldehydes range from 50-70%. 

C synthons, synthetic equivalents of which being the amino-acetaldehyde-derived metallated aminonitrile D bearing the chiral auxiliary (S,S)-53 and an a,P-unsaturated ester E, respectively. This should make it possible to open up a pathway to an enantioselective conjugate addition of an a-aminoacyl carbanion equivalent D to enoates in order to access the target 3-substituted 5-ainino-4-oxo esters. 

Ketols can also be formed enzymatically by cleavage of an aldehyde (step a, Fig. 14-3) followed by condensation with a second aldehyde (step c, in reverse). An enzyme utilizing these steps is transketolase (Eq. 17-15),132b which is essential in the pentose phosphate pathways of metabolism and in photosynthesis. a-Diketones can be cleaved (step d) to a carboxylic acid plus active aldehyde, which can react either via a or c in reverse. These and other combinations of steps are often observed as side reactions of such enzymes as pyruvate decarboxylase. A related thiamin-dependent reaction is that of pyruvate and acetyl-CoA to give the a-diketone, diacetyl, CH3COCOCH3.133 The reaction can be viewed as a displacement of the CoA anion from acetyl-CoA by attack of thiamin-bound active acetaldehyde derived from pyruvate (reverse of step d, Fig. 14-3 with release of CoA). 

Cyclocondensation of malonates and acetaldehyde derivative 227 in boiling ethanol in the presence of catalytic amounts of piperidine and acetic acid under nitrogen also afforded 6-oxo-6//-pyrido[l, 2-a]-pyrimidine-7-carboxylates 228 (91MIP3). 

It is worthy of note that - similarly to the proline catalyzed aldol reaction - the Mannich reaction can also be extended to an enantio- and diastereoselective process in which two stereogenic centers are formed in one step, although using non-chiral starting materials (Scheme 5.16) [22, 23, 26, 27, 28]. In these reactions substituted acetone or acetaldehyde derivatives, rather than acetone, serve as donor. In contrast with the anti diastereoselectivity observed for the aldol reaction (Section 6.2.1.2), the proline-catalyzed Mannich reaction furnishes products with syn diastereoselectivity [23]. A proline-derived catalyst, which led to the formation of anti Mannich products has, however, been found by the Barbas group [29]. 

The common name is acetaldehyde, derived from acetic acid.)... 

In at least one case, a substituted aminoacetal has been used. Wacker and Fritz31 reported the use of D-glucosamine [Eq. (14)] to form derivatives of tetrahydroisoquinoline. Carbons 1 and 2 of the sugar became carbons 3 and 4 of the isoquinoline, and the acetal oxygen became the 4-oxy substituent. This area of work has been retarded by the lack of readily available 2-aminoaldehyde acetals other than the simple acetaldehyde derivative. 

Do optically active 1-methyl-TIQs, as sketched in Fig. 32 for the synthesis of (7 )-salsolinol, originate from a Pictet-Spengler reaction of dopamine with acetaldehyde derive from ethanol, or are they the result of a Pictet-Spengler reaction of biogenic amines with pyruvic acid, as sketched in Fig. 33 Based on the accumulated data it seems reasonable to propose that optically active TIQs are formed by the pyruvic acid pathway, and that the pyruvic acids may be derived from an impaired glucose metabolism or an impaired amino acid metabolism. Whether the intermediate TIQ-1-carboxylic acids 91a,b are enzymatically decarboxylated to afford 64a,b in a different enantiomeric ratio, or whether optically active TIQs are formed by oxidative decarboxylation of TIQ 91 to DIQ 120, followed by an asymmetric reduction, remains open to question. 

However, in a recent publication, Shirinyan, Mnatsalianov, et al. (20) find that differences between the rates of vinyl acetate emulsion polymerisation observed with samples of similar polyvinyl alcohols manufactured by the same process In three different factories could be attributed to a condensation product of acetaldehyde derived from hydrolysis of residual vinyl acetate this gave rise to a conjugated ketone type ultra-violet spectrum and could be extracted from the polyvinyl alcohol under suitable conditions. This could be the uncontrolled factor which appears to have confounded nmuiy of the experiments reported here. Even more recently the same laboratory ( ) has reported that there Is an optimum sequence length of hydroxyl groups in the polyvinyl cdcohol-acetate block copolymer for polymerisation rate and dispersion stability. 

The methodologies outlined in Scheme 10.55 and similar approaches were applied to gain access to enantiomerically enriched A -hydroxylamines [137,138]. In the Abbott approach, treatment of acetaldehyde-derived mannofuranosyl nitrone 165b with metalated benzo[h]thio-phene selectively furnished addition product 171, which was further transformed to ( + )-(R)-zileuton 172 [137] (Scheme 10.56), a potent selective 5-lipoxygenase inhibitor [139,140]. 

Improvements to the basic commercial process also involve modifications to the purification stage and implementation of chemical treatment applications within that section, such as treatment with ozone, peroxides, or hydrogen [116-126]. These improvements are designed specifically to remove low levels of iodides, acetaldehyde, and acetaldehyde-derived impurities (i.e., crotonaldehyde and 2-ethylcrotonaldehyde) to reduce the concentration of these impurities in the final product. Removal of these impurities improves the acetic acid product quality [116-126]. 

GC/MS analysis of PFBOA-derivatives can be performed by either El or chemical ionization. Chemical ionization is performed in positive ion mode (PICI) using methane as a reagent gas. In this analysis, abundant protonated [M + H]+ ion of acetaldehyde-derivatives at m/z 240, diacetyl-mono derivatives at m/z 282 and of internal standard o-chlorobenzaldehyde derivatives at m/z 336, form, and an abundant formation of [M + H—18]+ ion of acetoin-derivatives at m/z 282, is observed. Mass spectra of acetaldehyde, diacetyl monooxime, acetoin and o-chlorobenzaldehyde PFB-derivatives recorded in the PICI analysis of a standard solution are reported in Figure 1.19. 

The incorporation of acetaldehyde derived bridges between anthocyanins and flavan-3-ols via acetaldehyde condensation reactions has been well described in fermented beverages such as red wine. The presence of acetaldehyde in alcoholic solutions is attributed to either oxidatative products of ethanol or microbial byproducts. In the case of cranbeny fruit and spray dried juice neither product was subjected to yeast fermentation. It becomes a concern then that die observed anthocyanin-pigments may be an arti ct of harvest, storage, juice processing or analytic techniques. 

Viitala K, Makkonen K, Israel Y, Lehtimaki T, Jaakkola O, Koivula T, Blake JE, Niemela O (2000) Autoimmune responses against oxidant stress and acetaldehyde-derived epitopes in human alcohol consumers. Alcohol Clin Exp Res, 24 1103-1109. 

In the mass spectrometric method it is usually most convenient to convert both the substrate and product to the same chemical species for isotopic analysis. This procedure, furthermore, eliminates the difficult corrections which would have to be applied for isotopic discrimination in the mass spectrometer. If the substrate or products contain the isotopes A and A9 in groups or substituents other than the reaction center, there may be complications from isotopic homogeneity. This has been pointed out previously.8 Recently Yankwich and Promislow70 have shown that there is a 1 per cent difference in the C18 content of the methyl and aldehyde carbons of acetaldehyde derived from the air oxidation of propane... 

Smith, J., Harris, T.M., Lloyd, R.S., Rizzo, C.J., and Stone, M.P. (2006) Stereospecific formation of interstrand carbinolamine DNA cross-links by crotonaldehyde- and acetaldehyde-derived a-CH3-y-OH-l,N2-propano-2 -deoxyguanosine adducts in the 5 -CpG-3 sequence. Chem. Res. Toxicol, 19, 195-208. 

Zhang, S., Villalta, P.W., Wang, M., and Hecht, S.S. (2006) Analysis of crotonaldehyde- and acetaldehyde-derived l,N2-propanodeoxyguanosine adducts in DNA from human tissues using liquid chromatography electrospray ionization tandem mass spectrometry. Chem. Res. Toxicol, 19, 1386-1392. 

Cheng, T.F., Hu, X., Gnatt, A., and Brooks, P.J. (2008) Differential blocking effects of the acetaldehyde-derived DNA lesion N2-ethyl-2 -deoxyguanosine on transcription by multisubunit and single subunit RNA polymerases. 

Early attempts to utilize acetaldehyde and monosubstituted acetaldehyde derivatives in the Darzens reaction were unsuccessful, presumably due to competitive base-catalyzed self-condensations of the aldehydes. It was subsequently reported Aat generation of the requisite bromo ester enolates with LHMDS at -78 °C provides a species which reacts with a variety of aldehydes and ketones to afford glycidic esters in good to excellent isolated yields (equation 25). ... 

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