Aldehydes arylacetals

In another type of oxidative decarboxylation, arylacetic acids can be oxidized to aldehydes with one less carbon (ArCH2COOH ArCHO) by tetrabutylammonium... 

In order to confirm the radical character of 51 and to extend its utility, oxidations of ary-lacetic acids to the corresponding ketones, aldehydes or alcohols have been conducted. Competitive decarboxylation reactions of phenylacetic acid and p-substituted phenylacetic acids were carried out. The ratio of the rate constants for the decarboxylation of various substituted phenylacetic acids relative to that of phenylacetic acid was found to decrease on decreasing the electron density at the benzylic carbon. Consequently, compound 51 shows an electrophilic oxidation ability towards arylacetic acids, giving a Hammett p value of —0.408. 

In another type of oxidative decarboxylation, arylacetic acids can be oxidized to aldehydes with one less carbon (ArCH2COOH — ArCHO) by tetrabutylammonium periodate. 23l< Simple aliphatic carboxylic acids were converted to nitriles with one less carbon (RCH2COOH — RC=N) by treatment with trifluoroacetic anhydride and NaNCU in FjCCOOH.239 See also 4-39. 

Reaction of aldehydes with ethyl diazoacetate normally results in the formation of [5-oxo esters. When a cationic Fe(II) Lewis acid is used as the catalyst, an unexpected 1,2-aryl shift results in the formation of a-formyl arylacetic acid ester 23, which is isolated as its enol tautomer (Scheme 8.6) [28]. The catalyst of this reaction,... 

ANILINES 4-Chloro-2-pbenylquliiazolme. ANNULENES Propaigyl aldehyde. ANTHRONES Pyiidene hydrochloride. APORPHINES 6-Methoxy-7-hydroxy-3,4-dihydroisoquinoliniuin methiodide. ARYLACETIC ACIDS Ceric acetate. ARYLACETYLENES n-Butylamine. Iodoethynyl(trimethyl)siIane. 

Benzylic oxidation. By this reagent combination in MeCN, benzyl ethers are oxidized to benzoic esters (11 examples, 81-93%). Arylacetic acids undergo oxidative decarboxylation which results in aromatic aldehydes (10 examples, 52-84%). ... 

Malone. G.R.. and Meyers. A.I., The chemistry of 2-chloromethyl-5,6-dihydro-l,3-oxazines. Grignard coupling metalation studies. A synthesis of a-chloro aldehydes and arylacetic acids, J. Org. Chem., 39. 618. 1974. 

Condensations of aryiacetic acids, arylacetates and arylacetonitriles with aromatic aldehydes and ketones proceed under standard Knoevenagel conditions, providing access to stilbenes or substituted stil-benes. - Thus 3-nitrobenzaldehyde and 4-nitrophenylacetic acid react in the presence of different amines to give (130), (131) and (132). The ratio of the products varies greatly with the amine used. (131) and (132) could easily be transformed into (130) in high yield. Reaction of arylacetates with o-hydroxybenzaldehydes yields the corresponding coumarins. The condensation of 2-hydroxy-4-meth-oxybenzaldehyde (133) with pyridylacetates like (134) yields 7-methoxy-3-pyridylcoumarins like (135) (Scheme 20). 

Phthalic anhydride, when used as the carbonyl component in the Peikin reaction, affords, on treatment with acetic anhydride and potassium acetate, phthalylacetic acid (15 equation 12) a-Arylacetic acids also react with aromatic aldehydes to afford a-arylcinnamic acids (Ogliaro modirication of the Pericin condensation, equation 7) this type of reaction presumably involves the formation of the mixed anhydride of phenylacetic acid and acetic acid and/or phenylacetic anhydride. This modirication is also illustrative of the equilibrium that is established between acid, acid salt and acid anhydrides under the conditions of the reaction. 

The condensation of rhodanine (42) with aldehydes is an important reaction closely related to the Er-lenmeyer azalactone synthesis (equation 22) the resulting condensation products are particularly useful intermediates for the preparation of various functionalized arylacetic acids and derivatives via standard manipulations of the nitrile (43), which is available as illustrated in Scheme 11. Similarly, aldehydes... 

Reaction with arylaeetic acids. Alkaline sodium hjrpochlorite solution oxidizes arylacetic acids to an aldehyde and/or a carboxylic acid containing one carbon atom less than the starting material. ... 

The reactions of aldehydes with carboxylate enolates are stereochemical-ly related to the Ivanov reaction (dianions of arylacetic acids -t carbonyl compounds), named after the Bulgarian chemist Dimitar Ivanov Popov (1894-1975). 

Arylacetic acids from ar. aldehydes ArCHO ArCHgCOOH... 

The calixarenes (e.g. methyl-p-tert-butylcahx[4]arylacetate in Table 7.3 and f in Fig. 7.8 are molecules that resemble a vase. They are synthesized by reaction of substituted phenols with aldehydes. The molecules have hydrophobic cavities which can hold sample ions. As an example, a sodium-sensitive electrode with polymer membrane has been designed as shown in Fig. 7.6, right (Diamond et al. 1988). 

Tetra-n-butylammonium periodate in refluxing dioxan represents an alternative method for oxidative decarboxylation, being capable of converting arylacetic acids into benzaldehydes and a-hydroxy acids into aldehydes in 50— 70% yields. A similar transformation of acids (RCH2CO2H) into aldehydes (RCHO) can be accomplished by conversion of the acid into a triazolium salt followed by oxidation with (diacetoxyiodo)benzene and base hydrolysis overall yields are fair. ... 

At least two other methods are available for preparing arylacetic acids from aromatic aldehydes. One involves the condensation of the aldehyde with rhodanine, and the other involves the formation of the... 

Arylacetic acids from ar. aldehydes ArGHO ArGH2GOOH via 5-oxazolones and 1,3,5-oxadiazines—Synthesis with addition of 1 G-atom s. 12, 794 ... 

---