Of aromatic aldehydes

Azlactones (anhydrides of a-acylamino acids) are formed by the condensation of aromatic aldehydes with acyl derivatives of glycine in the presence of acetic anhydride and anhydrous sodium acetate. Thus beiizaldehyde and acetyl-... 

Decarbonylation of aromatic aldehydes proceeds smoothly[71], Terephthalic acid (86), commercially produced by the oxidation of p-.xylene (85), contains p-formylbenzoic acid (87) as an impurity, which is removed as benzoic acid (88) by Pd-catalyzed decarbonylation at a high temperature. The benzoic acid produced by the decarbonylation can be separated from terephthalic acid (86) based on the solubility difference in water[72]. 

The behavior of aromatic aldehydes is typical Nitration of benzaldehyde takes place sev eral thousand times more slowly than that of benzene and yields m mtrobenzaldehyde as the major product... 

Aliphatic Aldehyde Syntheses. Friedel-Crafts-type aUphatic aldehyde syntheses are considerably rarer than those of aromatic aldehydes. However, the hydroformylation reaction of olefins (185) and the related oxo synthesis are effected by strong acid catalysts, eg, tetracarbonylhydrocobalt, HCo(CO)4 (see Oxo process). 

Schiff s bases of etbyleneimine dimer are obtained from the reaction of aromatic aldehydes, eg, ben2aldehyde [100-52-7] or furfural [98-01-00] and ethyleneimine (228). 

These reversible reactions are cataly2ed by bases or acids, such as 2iac chloride and aluminum isopropoxide, or by anion-exchange resias. Ultrasonic vibrations improve the reaction rate and yield. Reaction of aromatic aldehydes or ketones with nitroparaffins yields either the nitro alcohol or the nitro olefin, depending on the catalyst. Conjugated unsaturated aldehydes or ketones and nitroparaffins (Michael addition) yield nitro-substituted carbonyl compounds rather than nitro alcohols. Condensation with keto esters gives the substituted nitro alcohols (37) keto aldehydes react preferentially at the aldehyde function. 

Table 3. Concentration of Aromatic Aldehydes in Bourbon as Influenced by Barrel Treatment, Age, and Proof...

This reaction is favored by moderate temperatures (100—150°C), low pressures, and acidic solvents. High activity catalysts such as 5—10 wt % palladium on activated carbon or barium sulfate, high activity Raney nickel, or copper chromite (nonpromoted or promoted with barium) can be used. Palladium catalysts are recommended for the reduction of aromatic aldehydes, such as that of benzaldehyde to toluene. 

BORSCHE - BEECH Aromatic Aldehyde Synthesis Synthesis of aromatic aldehydes and of akyl aryl ketones from aldoximes or semcaibazones and aromatic dlazonum salts... 

GATTERMAN - KOCH Cartionylation Synthesis of aromatic aldehydes or ketones using cyanide salts or CO - HCI and Lewis adds. 

In general, imines are too reactive to be used to protect carbonyl groups. In a synthesis of juncusol, however, a bromo- and an iodocyclohexylimine of two identical aromatic aldehydes were coupled by an Ullman coupling reaction modi-fied by Ziegler. The imines were cleaved by acidic hydrolysis (aq. oxalic acid, THF, 20°, 1 h, 95% yield). Imines of aromatic aldehydes have also been prepared... 

Hammett treatments show good correlations with large negative p values for the hydrolysis of acetals of aromatic aldehydes. This is consistent with the development of a positive charge at the carbonyl center in the rate-determining step. 

Erlenmeyer reaction is the condensation of aromatic aldehydes with hippuric acid to form aziactones (important intermediates in the preparation of amino- and keto-acids)... 

DDQ, CH3CN, H2O (9 1), 0.5-6 h, 30-88% yield. Dithiane derivatives of aromatic aldehydes give thioesters in low yields dithiolanes are not effectively cleaved. 

In 1959, Crawford and Little reported superior yields of 3 in reactions of aromatic aldehydes by using isolated, crystalline 2-phenyloxazol-5-one (2, Ri = Ph) compared to direct reaction with hippuric acid (1, Ri = Ph). An early report by Boekelheide and Schramm on the use of ketones in the Erlenmeyer azlactone synthesis includes treatment... 

Recent work by Powers has suggested that in addition to the di-indolylphenylmethane derivatives, 3-aroylindoles are obtained by the action of aromatic aldehydes on the indole Grignard reagents. 

Aliphatic and aromatic aldehydes condensed with 2-amino-(62BRP898414), 5-amino- (80AJC1147), or 8-amino-l,2,4-triazolo[l,5-cjpyrimidines (68JOC530) to give the related Schiff bases. Treatment of the 2-amino-5-methyl-l,2,4-triazolo[l,5-c]quinazoline 11 with formaldehyde and piperidine in the presence of acetic acid gave the 2-hydroxymethyl-amino-5-(2-piperidinoethyl) derivative 172. Utilization of aromatic aldehydes and piperidine in this reaction gave the 2-arylideneamino-5-styryl derivatives 173 (68CB2106) (Scheme 67). 

It has been shown that ytterbium tris-(l )-(-)-l,l -binaphthyl-2,2 -diyl phospho-nate can catalyze the reaction of aromatic aldehydes with Danishefsky s diene to... 

Upon heating of a carboxylic ester 1 with sodium in an inert solvent, a condensation reaction can take place to yield a a-hydroxy ketone 2 after hydrolytic workup. " This reaction is called Acyloin condensation, named after the products thus obtained. It works well with alkanoic acid esters. For the synthesis of the corresponding products with aryl substituents (R = aryl), the Benzoin condensation of aromatic aldehydes is usually applied. 

Condensation of aromatic aldehydes with carboxylic anhydrides... 

The direct conversion of nitroalkenes into ketones is especially useful for the preparation of arylacetones. They are readily prepared by the condensation of aromatic aldehydes with nitroethane and by the subsequent Nef reaction. "Typical examples are presented in Eq. 6.22 and Eq. 6.23 the product of Eq. 6.23 is used for total synthesis of perylenequinone, calphosdn D, which is a potent inhibitor of protein kmase C. "... 

The preparation of mesitaldehyde is an example of a generally applicable method for the preparation of aromatic aldehydes by treatment of aromatic compounds with dichloromethyl methyl... 

Dichloromethyl methyl ether, 47, 47 in preparation of aromatic aldehydes,... 

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

The oxazaborolidines are easily prepared by heating ephedrine with borane dimethyl sulfide or the appropriate boronate ester. The aluminum reagent C is obtained by mixing ephedrine and trimethylaluminum. Borolidinc A is superior to its methyl derivative B and to the aluminum analog C. The diastereomeric borolidine obtained from borane and (S,S)-pseu-doephedrine failed to show any cnantioselectivity25. A variety of aromatic aldehydes can be enantioselectively alkylated in the presence of A, however, with heptanal the enantioselectivity is poor25. 

The M - 1 peak due to the loss of the aldehyde hydrogen by a-cleavage is usually abundant. The loss of 29 Daltons is characteristic of aromatic aldehydes. Peaks at m/z 39, 50, 51, 63, and 65 and the abundance of the molecular ion show that the compound is aromatic. Accurate mass measurement data indicate the presence of an oxygen atom. 

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