Acid To aldehyde

When the corresponding monobasic acid has a trivial name, the name of the aldehyde may be formed by changing the ending -ic acid or -oic acid to -aldehyde. Examples are... 

A completely different dipolar cycloaddition model has been proposed39 in order to rationalize the stereochemical outcome of the addition of doubly deprotonated carboxylic acids to aldehydes, which is known as the Ivanov reaction. In the irreversible reaction of phenylacetic acid with 2,2-dimethylpropanal, metal chelation is completely unfavorable. Thus simple diastereoselectivity in favor of u f/-adducts is extremely low when chelating cations, e.g., Zn2 + or Mg- +, are used. Amazingly, the most naked dianions provide the highest anti/syn ratios as indicated by the results obtained with the potassium salt in the presence of a crown ether. 

I.3.7.I.I. (/ )-Oxynitrilase-Catalyzed Addition of Hydrocyanic Acid to Aldehydes... 

Recently, the enantioselective addition of hydrocyanic acid to aldehydes, analogous to the synthesis of (/ )-cyanohydrins, yielding (.S)-cyanohydrins in very high optical purity, with (S )-oxynitrilase as catalyst, was reported20,21. 

Horner has applied the same reaction (55) to the continuing problem of converting carboxylic acids to aldehydes, the overall yield varying from 40—90% depending on R. 

White H, G Strobl, R Feicht, H Simon (1989) Carboxylic acid reductase a new tungsten enzyme catalyses the reduction of non-activated carboxylic acids to aldehydes. Eur J Biochem 184 89-96. 

Selective Hydrogenolysis of Esters and Acids to Aldehydes and Alcohols... 

In 1998, Miyaura reported a Rh(acac)(CO)2/dppp-catalyzed addition of aryl or alkenylboronic acids to aldehydes in aqueous organic mixtures under an inert atmosphere (Eq. 8.85).216 The use of electron-rich tri(tm-butyl)phosphine as ligand was found to be beneficial for obtaining good yields of the corresponding aldehyde addition products.217... 

Thiol esters undergo smooth reduction to give aldehydes by the Fukuyama hydrosilylation procedure, which is an alternative way to transform carboxylic acids to aldehydes. Upon treatment with Et3SiH and 10% Pd/C, a thioester underwent smooth reduction to give an aldehyde.409,410 For example, to a stirred mixture of thioester and Pd/C in acetone may be added Et3SiH at room temperature under an Ar atmosphere. Stirring is continued until the hydrogenolysis is complete (0.5-1 h) (Scheme 4.117). 

Addition of arylboronic acids to aldehydes using recoverable, water-soluble rhodium catalysts has also been reported.396... 

Reductions. Silicon hydrides such as 1, which can achieve intramolecular pentacoordination, show enhanced reducing properties. Thus they can reduce aldehydes or ketones to alcohols,1 and reduce carboxylic acids to aldehydes via thermal decomposition of a silyl carboxylate (equation I).2 Reaction of acid chlo-... 

Scheme 25 Cathodic reduction of activated aliphatic carboxylic acids to aldehydes (R alkyl, yields 70-82%) and ketones (R benzyl, yields 66- 72%).

According to Heathcock and his associates the configurational dependence on the ratio of Lewis acid to aldehyde must be related to steric effects, and they conclude that the aldols 103 and 102 result from the open transition states A and B, respectively (Scheme 9.33). If the Lewis acid is small, transition state A is preferred because it minimises gauche interactions about the forming bond, but if the Lewis... 

The hydrazide of 2,2-diphenyl-3-hydroxypropanoic acid was reduced with lithium aluminum hydride in 7V-ethylmorpholine at 100° to 3-amino-2,2-di-phenylpropanol in 72.5% yield [1145], Much more useful is reduction of N-arenesulfonylhydrazides of acids to aldehydes McFadyen-Stevens reduction) [284, 285] based on an alkali-catalyzed thermal decomposition according to Scheme 174. 

RAMP (R)-l-Amino-2-methoxyraethylpyrrolidine 1-Pyrrolidinamine, 2-(methoxyraethyl)-, (R)- 65, 173, 183 REDUCTION OF CARBOXYLIC ACIDS TO ALDEHYDES. 66, 121 RING EXPANSION, 65, 17... 

REDUCTION OF CARBOXYLIC ACIDS TO ALDEHYDES 6-OXODECANAL (Decanal, 6-oxo-)... 

Lithium aluminium hydride treatment of 9-acylcarba2oles also regenerates the carbazole. At low temperature, reduction of the acyl residue proceeds only as far as the aldehyde oxidation level, and this provides a means for the conversion of acid to aldehyde via the 9-acylcarbazole. This process has been described for the preparation of benzaldehyde, cin-namaldehyde, and various a-amino aldehydes. Reduction of 9-ethoxy-carbonylcarbazole gave 9-hydroxymethylcarbazole. Mechanistically... 

Nearly all the water-soluble vitamins are heterocyclic compounds. Among the first to be isolated was thiamine (vitamin Bi) (62), deficiency of which causes degenerative changes in the nervous system, including the multiple peripheral neuritis characteristic of beriberi. Thiamine deficiency can arise from decomposition of the vitamin by bacteria in the gut. In mammalian metabolism the hydroxy group of thiamine is esterified to give cocarboxylase (thiamine pyrophosphate) which catalyzes the decarboxylation of a-keto acids to aldehydes, acyloins or acids, and their transformation into acyl phosphates. 

Isatin has been used in the Strecker degradation of a-amino acids to aldehydes,434-437 and in the formation of benzaldehydes from benzyl-amines.431,435,438-440 These conversions have been the subject of a review, and mechanisms have been proposed.441 This formation of aldehydes from primary amines may, in part, explain some of the... 

Naphtho[2,3-b jthiophene derivatives (316) have been synthesized by this scheme, starting with phthalic anhydride, which could be reacted with thiophene under Friedel-Crafts conditions to give (315) (52JA4353). By the same scheme, anthra[2,3-bjthiophene (318) was obtained from (317) in 51% yield, by reduction of the acid to aldehyde and cyclization in PPA (81JHC967). 

Dehydroxylation (see Deoxygenation, Reduction of carboxylic acids to aldehydes)... 

Arene(tricarbonyl)chromium complexes, 19 Nickel boride, 197 to trans-alkenes Chromium(II) sulfate, 84 of anhydrides to lactones Tetrachlorotris[bis(l,4-diphenyl-phosphine)butane]diruthenium, 288 of aromatic rings Palladium catalysts, 230 Raney nickel, 265 Sodium borohydride-1,3-Dicyano-benzene, 279 of aryl halides to arenes Palladium on carbon, 230 of benzyl ethers to alcohols Palladium catalysts, 230 of carboxylic acids to aldehydes Vilsmeier reagent, 341 of epoxides to alcohols Samarium(II) iodide, 270 Sodium hydride-Sodium /-amyloxide-Nickel(II) chloride, 281 Sodium hydride-Sodium /-amyloxide-Zinc chloride, 281 of esters to alcohols Sodium borohydride, 278 of imines and related compounds Arene(tricarbonyl)chromium complexes, 19... 

The reductions in this section are mostly those of acids to aldehydes they are naturally few, since oxygenated compounds are not usually obtained by reduction of more highly oxygenated substances the reverse process is much more often employed. 

In the McFadyen-Stevens reaction, microwave irradiation has also been employed to convert carboxylic acids to aldehydes via the p-toluenesulphonyl hydrazides65. The p-toluenesulphonyl hydrazide is mixed with sodium carbonate, glass powder and ethylene glycol, and pre-irradiated at 150 W for a few minutes before the actual reaction conditions were applied. The reaction was successfully used in the synthesis of the alkaloid Nauclefidine (Scheme 4.40). 

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