Butanone 4- Hydroxy-2-, formation

The addition of phenyllithium to 3-hydroxy-l,3-diphenyl-1-butanone (4. R1 = R3 = C6HS R2 = H) leads to the predominant formation of either one or the other diastereomer, depending on the reaction temperature146. Thus, for this type of addition reaction there are at least two competing mechanisms which have quite different activation entropies147. 

In general, pyruvate decarboxylase (EC 4.1.1.1) catalyzes the decarboxylation of a 2-oxocar-boxylic acid to give the corresponding aldehyde6. Using pyruvic acid, the intermediately formed enzyme-substrate complex can add an acetyl unit to acetaldehyde already present in the reaction mixture, to give optically active acetoin (l-hydroxy-2-butanone)4 26. Although the formation of... 

Several products were also detected in base-degraded D-fructose solution acetoin (3-hydroxy-2-butanone 62), l-hydroxy-2-butanone, and 4-hydroxy-2-butanone. Three benzoquinones were found in the product mixture after sucrose had been heated at 110° in 5% NaOH these were 2-methylbenzoquinone, 2,3,5-trimethylbenzoquinone, and 2,5-dimethyl-benzoquinone (2,5-dimethyl-2,5-cyclohexadiene-l,4-dione 61). Compound 62 is of considerable interest, as 62 and butanedione (biacetyl 60) are involved in the formation of 61 and 2,5-dimethyl-l,4-benzenediol (63) by a reduction-oxidation pathway. This mechanism, shown in Scheme 10, will be discussed in a following section, as it has been proposed from results obtained from cellulose. 

From the base-catalyzed degradation of D-fructose (pH 8.0), Shaw and coworkers147 identified 18 compounds, none of which was (a) isomeric with the starting material, or (b) a simple dehydration product. Among the products, the hydroxy-2-butanones and 1-hydroxy-2-propanone (acetol) were shown to participate in forming the carbo-cyclic products identified, but the mechanism of their formation was not elucidated. Several furan derivatives were isolated, but no lactic acid was isolated. In a similar study but with weak acid,41 most of the products were formed by a combination of enolization and dehydration steps, with little fragmentation. 

As mentioned previously, the cyclization of phenethyl ketone oximes with [Bu4N]Re04 and CF3SO3H and the cyclic imine formation from 0-sulfonyl oximes both proceed by intramolecular S 2-type reaction on the nitrogen atom of the oximes (Scheme 33). ° In contrast, both of the E- and Z-isomers cyclized smoothly and only 8-hydroxyquinoline was obtained regioselectively without forming 6-hydroxy derivatives. These phenomena are not consistent with a nucleophilic substitution reaction, and the cyclization of 0-2,4-dinitrophenyloxime 80a seemed to proceed by another reaction pathway (Scheme 37). To check isomerization of the 0-2,4-dini-trophenyloxime 84, the Z-isomer was treated with NaH and m-cresol. The isomerization of (Z)-84 hardly occurred, but 4-phenylbutan-2-one azine (85) and 4-phenyl-2-butanone (86) were obtained in 27 and 11%... 

To test the volatile heterocyclic conq)ounds formation under low temperature condition, 0.01 mol of one of the following carbonyl compounds including a-hydroxyketones (3-hydroxy-2-butanone, 0.88 g l-hydroxy-2-propanone, 0.74 g l-hydroxy-2-butanone 0.88g) and a-dicarbonyls (2,3-butanedione, 0.86 g 2,3-pentanedione 1.00 g) and 0.02 mol of ammonium sulfide (20% wt/wt solution in water) were dissolved in 25 mL distilled water and reacted at 25°C for 2 hours. Immediately follow the reactions, the mixtures were cooled and extracted with methylene chloride three times, dried over anhydrous sodium sulfate, and then concentrated under a stream of N2 for further GC and GC/MS analyses. 

Proposed reaction mechanism of l-hydroxy-2-propanone or l-hydroxy-2-butanone with ammonium sulfide is shown in Figure 5. 2-Iminoalcohols, which were derived from the reaction of ammonia and a-hydroxyketones, were condensed with another molecule of a-hydroxyketone to form 2-(l-hydroxymethyl)-2,4-dialkyl-3-oxazolines. The substitution of -OH group with -SH group resulted in the formation of 2-(l-hydroxyemthyl)-2,4-dialkyl-3-thiazolines. No 2-(l-mercaptomethyl)-substituted isomers were found in either reaction. Upon heating, these intermediates were further converted to the corresponding oxazolines, oxazoles, thiazolines and thiazoles. 

An interesting end product, tetramethylpyrazine was also presented in the reaction mixture (27.3% of peak area of the total volatiles). Previous study of the model reaction of 2,3-butanedione and ammonium acetate did not yield any tetramethylpyrazine. It is probably due to the reducing environment provided by H2S which reduced 2,3-butanedione to 3-hydroxy-2-butanone. This explained that both 3-hydroxy-2-butanone and 3-mercapto-2-butanone were found in the reaction mixture. This study also supported the mechanism proposed by Elmore and Mottram 10) who observed that, during the reactions of hydroxyketones with aldehydes and ammonium sulfide, the formation of thiazoles was discouraged due to reducing environment provided by H2S derived from ammonium sulfide. It is also interesting to note that con aring to previous a-hydroxyketone series tetramethylpyrazine was present at trace levels whereas in the a-dicarbonyl series it was the major product under comparable tenq)erature conditions. The reason for this observed phenomenon is not obvious. It is possible that in the reaction system of acetoin and ammonium sulfide, the... 

It has been proved experimentally that gradual reduction of the primary and the secondary hydroxyl groups a-disposed to the carbonyl group is the major pathway operative with L-gZi/cero-tetrulose (20), occurring in two subsequent, two-electron steps, with formation of 1-deoxy-L-gZycero-tetrulose (21) and 4-hydroxy-2-butanone (22). Furthermore, it has been established that the carbonyl groups of L-gZycero-tetru-... 

Percent product distribution butanone 80.8 1.46, 2-hydroxy-2-methyl-butanal 4.6 0.1, l,2-dihydroxy-2-methyl-butane 14.3 0.3. The addition of OH at the double bond of 2-methyl-1-butene occurs to 10.5 % at the inner and to 89.5 % at the outer position. This results mainly in the formation of a tertiary hydroxyalkyl peroxy radical, which carries no abstractable hydrogen at the... 

Applying this protocol, enantioselective aldol reactions became feasible under reasonable conditions with fair chemical yields of P-hydroxy ketones 286 in up to 93% ee (Scheme 5.81) [142a]. For the unbranched aliphatic ketone butanone, the control of regiochemistry in favor of the formation of the less substituted enolate - without preceding kinetic deprotonation step - is remarkable. When applied to a-hydroxyacetophenone, nfi-configured aldol adducts 287 formed as the major diastereomers, the enantiomeric excess amounting to 90-95%. 

The formation of 2,3-dimethyl-N-vinylpyrrole from l-hydroxy-2-methyl-3-butanone oxime and 2-methyl-N-vinylpyrrole from 2-hydroxy-2-methyl-4-pentanone... 

The formation of 2-(2-propenyl)-N-vinylpyrrole from 2-methyl-l-hydroxy-3-butanone oxime and 2-methyl-l-vinyloxy-3-butanone oxime is apparently due to p-elimination of water or vinyl alcohol from the corresponding oximes or intermediate 2-hydroxy(vinyloxy)propyl-N-vinylpyrroles (Scheme 1.74). 

In the presence of a strong base such as LDA, the a-carbon of acetic acid esters can react with the carbonyl group of aldehydes or ketones to give j8-hydroxy esters, which may or may not be dehydrated to a,j8-unsaturated esters. This type of reaction has been exploited for the preparation of racemic [2- C]mevalonolactone (64) (Figure 6.25) and the benzofuran[l- C]acetamide PD 126,212 (67)". In the first case a-deprotonated trimethyl-silyl [2- C]acetate was treated with l-trimethylsilyloxy-3-butanone. Acidic work-up resulted in hydrolytic cleavage of the TMS groups and formation of the lactone system... 

Baker et al. (2004a) discussed formation of hydroxycarbonyls from alkanediols for example, l-hydroxy-2-butanone is formed in the oxidation of 1,2-butanediol. 

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