Aldehyde acid reaction

These reactions at particular functional groups of the sample molecule are closely related in an inverse sense with those reagents which bring their own functional group into the molecule. The numerous aldehyde — acid reactions are an example. Numerous monographs of such reactions are already included in Volume la. Their reac-... 

The aldehyde acid reactions have already been described generally in Chapter 2. There it was pointed out that a nucleophilic attack at a carbonyl group is particularly easy when this is attached to an aromatic ring that bears an electron withdrawing group at position 4. The reactivity of the carbonyl group is greatly increased in acid medium ... 

The general aspects of the aldehyde-acid reaction were discussed in Chapter 2. Thus it is readily understood that catechins, for example, can react with aromatic aldehydes in the presence of strong acids to yield colored triphenylmethane dyes [26]. 

Hoesch synthesis A variation of the Gattermann synthesis of hydroxy-aldehydes, this reaction has been widely applied to the synthesis of anthocyanidins. It consists of the condensation of polyhydric phenols with nitriles by the action of hydrochloric acid (with or without ZnCl2 as a catalyst). This gives an iminehydrochloride which on hydrolysis with water gives the hydroxy-ketone. 

Aldehyde Hydrogen Reactions. The hydrogen of the aldehyde groupis readily oxidized to OH, forming benzoic acid [65-85-0]. 

The treatment of 3-benzoyl-2-phenylisoxazolidine with strong base generated an aldehyde and a ketimine <74X1121). Under these conditions dimethyl 2-a-methoxyisoxazolidine-3,3-dicarboxylic acid (186) produced isoxazoline-2-carboxylic acid. Reaction of the monomethyl amide (187) gave the corresponding isoxazoline-2-carboxamide (Scheme 60). CD was used in the conformational studies <79X213). 

Substitution reactions by the ionization mechanism proceed very slowly on a-halo derivatives of ketones, aldehydes, acids, esters, nitriles, and related compounds. As discussed on p. 284, such substituents destabilize a carbocation intermediate. Substitution by the direct displacement mechanism, however, proceed especially readily in these systems. Table S.IS indicates some representative relative rate accelerations. Steric effects be responsible for part of the observed acceleration, since an sfp- caibon, such as in a carbonyl group, will provide less steric resistance to tiie incoming nucleophile than an alkyl group. The major effect is believed to be electronic. The adjacent n-LUMO of the carbonyl group can interact with the electnai density that is built up at the pentacoordinate carbon. This can be described in resonance terminology as a contribution flom an enolate-like stmeture to tiie transition state. In MO terminology,.the low-lying LUMO has a... 

Reaction with water to yield a carboxylic acid Reaction with an alcohol to yield an ester Reaction with ammonia or an amine to yield an amide Reaction with a hydride reducing agent to yield an aldehyde or an alcohol... 

Lithium aluminum hydride, reaction with aldehydes, 610 reaction with carboxylic acids. 611-612... 

Chloroacetic acid, reaction with salicyl-aldehyde, 46, 28 Chloroacetone, 46, 3 Chloroacetyl fluoride, 45, 6 o-Chloroacetyl isocyanate, 46,16 -Chloroaniline, reaction with carbon disulfide and aqueous ammonia,... 

When primary nitro compounds are treated with sulfuric acid without previous conversion to the conjugate bases, they give carboxylic acids. Hydroxamic acids are intermediates and can be isolated, so that this is also a method for preparing them. Both the Nef reaction and the hydroxamic acid process involve the aci form the difference in products arises from higher acidity, for example, a difference in sulfuric acid concentration from 2 to 15.5 M changes the product from the aldehyde to the hydroxamic acid. The mechanism of the hydroxamic acid reaction is not known with certainty, but if higher acidity is required, it may be that the protonated aci form of the nitro compound is further protonated. 

Similar kinetics are obtained with a-methylacraldehyde , but with croton-aldehyde the reaction is essentially first order in Mn(III), tending to zero-order only at relatively high [Mn(Ill)]. The oxidation of acraldehyde is viewed as a rapid reaction preceded by a slow acid-catalysed hydration, viz. 

The aerobic reduction of aryl and alkyl carboxylates to the corresponding aldehydes. The reaction involves formation of an acyl-AMP intermediate by reaction of the carboxylic acid with ATP NADPH then reduces this to the aldehyde (Li and Rosazza 1998 He et al. 2004). The oxidoreductase from Nocardia sp. is able to accept a range of substituted benzoic acids, naphthoic acids, and a few heterocyclic carboxylic acids (Li and Rosazza 1997). 

Reactions of partial electrochemical oxidation are of considerable interest in the electrosynthesis of various organic compounds. Thus, at gold electrodes in acidic solutions, olefins can be oxidized to aldehydes, acids, oxides, and other compounds. A good deal of work was invested in the oxidation of aromatic compounds (benzene, anthracene, etc.) to the corresponding quinones. To this end, various mediating redox systems (e.g., the Ce /Ce system) are employed (see Section 13.6). 

The stereochemistry was controlled by Lewis acid-induced addition of these allylic silanes to aldehydes. The reaction of the silane with O-protected (S)-3-hydroxy-2-methylpropanal provides 15. The silane reacted with the benzyl-protected analog to provide 16. 

The spirobenzylisoquinoline 171b derived from berberine (15) (Section IV,A,1) was oxidized with m-chloroperbenzoic acid to the /V-oxide 389, which was treated with trifluoroacetic anhydride to afford dehydrohydrastine (370) in 56% overall yield (Scheme 71) through the Polonovski reaction (187). Holland et al. (188,189) reported the reverse reaction from dehydrophthalides to spirobenzylisoquinolines, namely, 370 was reduced with diisobutylalu-minum hydride to give a mixture of two diastereoisomeric spirobenzylisoquinolines 320 and 348 via the enol aldehyde. This reaction was applied to synthesis of various spirobenzylisoquinoline alkaloids such as (+)-sibiricine (352), ( + )-corydaine (347), (+ )-raddeanone (354), ( )-yenhusomidine (359), (+ )-ochrobirine (343), and ( )-yenhusomine (323). 

Table 3 indicates that 5%Pt,l%Bi/C is active for three reaction cycles in the selective oxidation of the chosen alcohols. For primary alcohols the use of water as solvent can promote the aldehyde to carboxylic acid reaction (3). This effect is observed in the selective oxidation of 1-octanol where octanoic acid is formed with 97% selectivity in the first cycle dropping to 81% in the third. In the selective oxidation of geraniol only citral is observed as the oxidation product. The presence of the double bond stabilises the aldehyde even in the presence of... 

In a similar way, Carreaux and coworkers [53] used 1-oxa-l,3-butadienes 4-155 carrying a boronic acid ester moiety as heterodienes [54], enol ethers and saturated as well as aromatic aldehydes. Thus, reaction of 4-155 and ethyl vinyl ether was carried out for 24 h in the presence of catalytic amounts of the Lewis acid Yb(fod)3 (Scheme 4.33). Without work-up, the mixture was treated with an excess of an aldehyde 4-156 to give the desired a-hydroxyalkyl dihydropyran 4-157. Although this is not a domino reaction, it is nonetheless a simple and useful one-pot procedure. 

If the alkenes and acetylenes that are subjected to the reaction mediated by 1 have a leaving group at an appropriate position, as already described in Eq. 9.16, the resulting titanacycles undergo an elimination (path A) as shown in Eq. 9.58 [36], As the resulting vinyltitaniums can be trapped by electrophiles such as aldehydes, this reaction can be viewed as an alternative to stoichiometric metallo-ene reactions via allylic lithium, magnesium, or zinc complexes (path B). Preparations of optically active N-heterocycles [103], which enabled the synthesis of (—)-a-kainic acid (Eq. 9.59) [104,105], of cross-conjugated trienes useful for the diene-transmissive Diels—Alder reaction [106], and of exocyclic bis(allene)s and cyclobutene derivatives [107] have all been reported based on this method. 

SUCCINIMIDE, N-IODO-, 42, 73 Sulf anilic acid, reaction of the diazonium salt with substituted benzyl alcohols to give aldehydes, 44,. 4 Sulfoacetic acid, 44, 102 Sulfonation of pyridine, 43, 97... 

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