Arenes aromatic aldehydes

The reductive transformation of arene carboxylates to the corresponding aldehydes under aerobic conditions has already been noted. In addition, aromatic aldehydes may undergo both reductive and oxidative reactions, with the possibility of decarboxylation of the carboxylic acid formed ... 

Arenes, polyalkyl, oxidation with per-oxytrifluoroacetic acid and boron trifluoride, 48, 89, 90 Arenesulfonyl chlorides, reaction with 3-amino-3-pyrazoline, 48, 11 Aromatic aldehydes. Mesitalde-HYDE, 47, 1... 

Oxidation of hydrazines 9-33 Dimerization of arenes 9-37 Reduction of aromatic aldehydes 9-43 Reduction of aromatic acids... 

Aromatic aldehydes. Acetone cyanohydrin can be used in place of hydrogen cyanide in the Gattermann reaction for formylation of arenes.1 Example ... 

Arene)tricarbonylchromiums in cycloadditions, 5, 243 in higher-order cycloadditions, 5, 244 in silsesquioxanes, 5, 252 Aromatic acetylenes, silylformylation, 11, 477 Aromatic aldehydes, diastereoselective coupling reactions, 11,44... 

In aromatic aldehydes and ketones, electron donating substituents on the arene ring retard acetal formation whereas electron withdrawing substituents facilitate it. 

This amphiphilic conjugate alkylation has been used successfully for nucleophilic alkylation of electron deficient arenes, on the basis of the unprecedented conjugate addition of organolithiums to aromatic aldehydes and ketones by complexation with ATPH [136], Thus, initial complexation of benzaldehyde or acetophenone with ATPH and subsequent addition of organolithiums affords 1,6 adducts with high selectivity, as illustrated in Sch. 99. 

The electrophilic formylation of arenes with CO in the presence of acids (Gatterman-Koch conditions) is an efficient method for preparing aromatic aldehydes. HF-SbFs-SO2CIF is the most active system for this reaction [82]. It has been demonstrated that even diformylation can be achieved on polymeric aromatics such as biphenyl with the use of fluoroantimonic acid (Eq. 36) [83]. 

The classic SsAi substitution of activated aryl halides by protected cyanohydrin anions provides substituted benzophenones. Another procedure for the arylation of protected cyanohydrin anions involves the use of aromatic substrates activated as their rr-chromium tricarbonyl complexes. - Addition of the anion of (32) to the 1,3-dimethoxybenzene complex, for example, leads principally to the meta-suh-stituted isomer (33 equation 20). Preferential meta regioselectivity is also noted with other -rr-chromium tricarbonyl complexes of arenes. Other arylations of cyanohydrin anions include interesting but synthetically limited additions at the a-position of quinoline N-oxides. In a similar manner, cyanohydrin carbonates of aromatic aldehydes react with A -oxides of quinoline and isoquinoline. ... 

Given a Lewis structure, a condensed formula, or a line drawing for an organic compound, identify it as representing an alkane, alkene, alkyne, arene (aromatic), alcohol, carboxylic acid, ether, aldehyde, ketone, ester, amine, or amide. 

At a lower oxidation level, orffto-hydroxy-acyl-arenes undergo base-catalysed aldol condensations with aromatic aldehydes to give chalcones, °° which can be cyclised to 2,3-dihydro-chromones via an intramolecular Michael process the dihydro-chromones can in turn be dehydrogenated to produce chromones by a variety of methods, for example by bromination then dehydrobromination or by oxidation with the trityl cation, iodine, dimethyldioxirane or iodobenzene diacetate. ° ... 

Usually, the condensation between arenes and aldehydes is carried out in the liquid phase, and large pore zeolites are necessary in order to make the reaction occur at an acceptable rate in the condensed phase. When formaldehyde is the reactant, one main problem is the presence of water, since the aqueous solution of formaldehyde (formalin) is the simplest, cheapest and most widely available reactant for use on an industrial scale. This implies the need for hydrophobic zeolites, in order to avoid preferential filling of the pores by more polar water molecules rather than by the aromatic substrate [8,9]. The objective of the work reported here was to compare the performance of different solid acids, and to study the effect of operating parameters on catalytic performance in the hydroxymethylation of guaiacol with formaldehyde catalyzed by a commercial dealuminated, and thus more hydrophobic, H-mordenite zeolite. 

The efficiency of the DABCO-catalyzed MBH reaction of activated olefins with aromatic aldehydes can be increased significantly by complexation of the arene to the electrophilic Cr(CO)3 group, and the dependence of diastereo-selectivity on the nature of the ortho substituent was observed. Excellent diastereoselectivities have been achieved in reactions of tricarbonylchromium... 

Also, the use of prolinamide derivatives bearing a stereogenic axis such as in the spiro compound 57 (Fig. 4.4) has been further explored in the reaction of acetone (26.5 equiv.) with several aliphatic and aromatic aldehydes at -25°C. Although its high activity permitted to reduce the amount of catalyst to only 1 mol%, the results were in general modest (50-87% yield, 19-76% ee) [116]. More complicated chiral calix[4]-arene based prolinamide 58 (10 mol%) required the use of acetic acid (20 mol%) as co-catalyst to give the aldol products derived from cyclohexanone (7.3 equiv.) and several aromatic aldehydes, with moderated yields and selectivities (35-93% yield, 66-88% de, 50-79% ee) [117],... 

Also calix[4]arene has been incorporated to the hydroxy moiety of 4-hydroxyproline to give componnd 98 (Fig. 4.13). This system (2 mol%) have been applied as catalyst in the aldol reaction between cyclohexanone with different aromatic aldehydes in water at 25°C. Generally, moderate yields, diastereo- and enantioselectivities were obtained, being highly dependent on the aromatic substitution. Whereas electron rich aromatic aldehydes afforded mainly the syn-aHAoi, the... 

Synthetic applications of [4+2] photocycloadditions have not been extensively developed. It has been observed, however, that intramolecular photocycloaddition of arenes and allenes proceeds preferentially via the [4+2] reaction mode. This process appears to be reasonably general across a diverse range of allenes attached to aromatic aldehydes and ketones with a variety of tethers. Thns, the protected aniline 36 undergoes para-cycloaddition to give the intriguing bridged polycyclic product 37 (Scheme 15.13) [34]. Mechanistic details of this and related transformations have not yet been reported. 

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