Propionaldehyde, reduction

Reduction. Because of a lack of discrimination between the double bond and carbonyl moieties, direct hydrogenation of acrolein leads to the production of mixtures containing propyl alcohol, C HgO [71-28-8] propionaldehyde, C H O [123-38-6J, and aHyl alcohol, C H O [107-18-16]. Both the... 

The vapor-phase reduction of acrolein with isopropyl alcohol in the presence of a mixed metal oxide catalyst yields aHyl alcohol in a one-pass yield of 90.4%, with a selectivity (60) to the alcohol of 96.4%. Acrolein may also be selectively reduced to yield propionaldehyde by treatment with a variety of reducing reagents. 

This procedure is representative of a new general method for the preparation of noncyclic acyloins by thiazol ium-catalyzed dimerization of aldehydes in the presence of weak bases (Table I). The advantages of this method over the classical reductive coupling of esters or the modern variation in which the intermediate enediolate is trapped by silylation, are the simplicity of the procedure, the inexpensive materials used, and the purity of the products obtained. For volatile aldehydes such as acetaldehyde and propionaldehyde the reaction Is conducted without solvent in a small, heated autoclave. With the exception of furoin the preparation of benzoins from aromatic aldehydes is best carried out with a different thiazolium catalyst bearing an N-methyl or N-ethyl substituent, instead of the N-benzyl group. Benzoins have usually been prepared by cyanide-catalyzed condensation of aromatic and heterocyclic aldehydes.Unsymnetrical acyloins may be obtained by thiazol1um-catalyzed cross-condensation of two different aldehydes. -1 The thiazolium ion-catalyzed cyclization of 1,5-dialdehydes to cyclic acyloins has been reported. 

An interesting reduction of aldehydes takes place on treatment with a reagent prepared from titanium trichloride and potassium [206] or magnesium [207] in tetrahydrofuran propionaldehyde gave a 60% yield of a mixture of 30% cis- and 30% /ronj-3-hexene [207]. 

Yoshida et al. [356] show the presence of O" and OJ on V2Os supported by Si02. With strong reduction, it is mainly O. It was proved that reaction of 02 with propene gives rise to aldehydes (propionaldehyde, acrolein and formaldehyde) at temperatures below 150°C. Yoshida et al. [357] confirm this and find that oxygen at room temperature is mainly adsorbed as molecular oxygen, only 10% is the sum of O and 02. O" is the oxygen species reactive towards carbon monoxide, 02 is not. 

Acrolein is a highly reactive compound because both the double bond and aldehydic moieties partidpate in a variety of reactions, including oxidation, reduction, reactions with alcohols yielding alkoxy propionaldehydes,... 

In the examples of reductions of XCH2CHO mentioned above, hydration occurs both as antecedent and interposed reactions. The change of the second reduction step with pH is similar to that observed for acetaldehyde, but not quantitatively identical. This indicates that the second dehydration step is preceded here by a proton transfer. The rate of the proton transfer involving the carbanion formed as a primary electrolysis product governs the height of the acetaldehyde wave 84, 85). In the reduction of cinnamaldehyde, where only the hydration is interposed between the reductions of cinnamaldehyde and of 3-phenyl-propionaldehyde 87), the pH-dependence of the more negative wave of cinnamaldehyde is quantitatively identical with the pH-dependence of... 

S)-Proline also catalyzed the Mannich-type reactions of unmodified aldehydes and N-PMP-protected imines to afford the corresponding enantiomerically enriched / -aminoaldehydes at 4 °C (Table 2.13) [71b]. The products were isolated after reduction with NaBH4, though oxidation to the / -amino acid is also possible. These reactions also provided the syn-isomer as the major diastereomer with high enantioselectivities, and proceeded well in other solvents (e.g., dioxane, THF, Et20). In the reaction of propionaldehyde and the N-PMP-imine of 4-nitrobenzaldehyde in DMF, the addition of water (up to 20%, v/v) did not affect the enantioselectivity. Similar results were obtained for the (S)-proline-catalyzed Mannich-type reactions with the glyoxylate imine where water did not reduce enantioselectivity [71b]. However, the enantioselectivity of the reaction of propionaldehyde and the N-PMP-imine of benzaldehyde in DMF was decreased by the addition of water or MeOH [71b]. 

Conditions Entries 1-3 To a mixture of ArCHO (0.5 mmol), 4-methoxyaniline (0.5 mmol), and (S)-proline (0.15 mmol) in DMF (3 mL), donor aldehyde (5.0 mmol) in DMF (2 mL) was slowly added (0.2 mL min-1) at —20 °C. The mixture was stirred at the same temperature for 4-10 h. The mixture was diluted with Et20 and reduction performed by addition of NaBH4 [71b]. Entries 4 and 5 After stirring a solution of ArCHO (1.0 mmol), 4-methoxyaniline (1.1 mmol), and (S)-proline (0.1 mmol) in N-methyl-2-pyrrolidinone (1.0 mL) for 2 h at rt, propionaldehyde (3.0 mmol) was added to the mixture at -20 °C, and stirring was continued for 20 h at the same temperature. The reaction was worked-up and reduction with NaBH4 performed without purification [82]. 

Method B After stirring a solution of ArCHO (1.0 mmol), 4-methoxyaniline (1.1 mmol), and (S)-proline (0.1 mmol) in N-methyl-2-pyrrolidinone (1.0 mL) for 2 h at r.t., propionaldehyde (3.0 mmol) was added to the mixture at — 20 °C, and stirring continued for 20 h at the same temperature. The reaction was worked-up and reduction with NaBH4 was performed without purification. 

The preparation of tertiary amines by reductive alkylation of ammonia appears to find only limited application. Triethylamine and tripropylamine were prepared by hydrogenation of acetaldehyde and propionaldehyde, respectively, in the presence of ammonia over platinum catalyst.38 A high yield (84.1% by GC) of trinonylamine was... 

Because of the current interest in anthracycline antibiotics, Sutherland et al. have extended the earlier studies to leuco-5-hydroxyquinizarins (3). When 3 is generated in situ by alkaline dithionite reduction, it reacts with propionaldehyde to give the... 

The reduction of a carboxyl group to an aldehyde group can be effected by a reductive desulfurization of the thiol ester with Raney nickel. The thiol esters are prepared by the reaction of the acyl chloride with an excess of ethyl mercaptan in pyridine or by reaction with lead mercaptide in dry ether. The hydrogenolysis is then carried out by refluxing an ethanol ic solution of the thiol ester with Raney nickel for 6 hours. By this new synthesis, propionaldehyde and benzaldehyde have been prepared in 73% and 62% yields, respectively. ... 

Reaction between the anion of 266 and propionaldehyde gave 267 as the single product. Reduction of267 by sodium borohydride to 268 was stereospecific, and hydrogenolysis of 268 provided (-l-)-/3-conhydrine (269)... 

Figure 14. Plot of logfcobs for the acid-catalyzed reduction of aldehydes and ketones by AcrH2 in the presence of HCIO4 (2.7 x 10 M) in MeCN at 333 K vs. logfcet for the acid-catalyzed electron transfer from [Ru(bpy),il + to the same series of substrates in the presence of HCIO4 (2.0 M) at 298 K. Numbers refer to the aldehydes and ketones (1, acetaldehyde 2, propionaldehyde 3, butyraldehyde ...

Among the reactions of acrolein which are important in determining its structural formula are those in which it is reduced to allyl alcohol and to propionaldehyde or oxidised to acrylic acid. Reduction is most conveniently carried out by means of aluminium amalgam, while atmospheric oxygen is sufficient to oxidise it. More powerful oxidants cause profound breakdown of the molecule thus nitric acid forms oxalic and glycollic acids and chromic acid mixture formic acid and carbon dioxide. 

Adkins and Krsek noted that certain a,/3-unsaturated carbonyl compounds undergo reduction rather than hydroforraylation. Thus crotonaldehyde and acrolein are reduced to n-butyraldehyde and propionaldehyde, respectively, and methyl vinyl ketone is reduced to methyl ethyl ketone. Orchin and co-workers found that if the reaction is carried out at a higher temperature (180-185°) the carbonyl group is reduced as well. Indeed application of the 0x0 reaction to an alcohol leads to homologation ... 

In seeking to synthesize methionine-a-C , Claus and Morgenthau explored the possibility of converting S-methylmercaptopropionitrile into 8-methylmercapto-propionaldehyde, but Stephen reduction and direct reduction with lithium aluminum... 

An aldol condensation (selectivity 100 1) between e reagent 106a (produced from optically active mandelic acid), known to induce (f ) chirality, and propionaldehyde, followed by desilylation and oxidative cleavage of the resulting a-hydroxy ketone gave the p-hydroxy acid 107 in 85% yield. Esterification, silylation, and a reduction-oxidation sequence then afforded a 75% overall yield... 

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