Substituted benzaldehydes derivatives

Lucchi , who studied the oxidation of substituted benzaldehyde derivatives found that chlorine atoms in the meta and para position accelerate the reaction and alkyl groups retard the oxidation. A Hammett plot of Lucchi s data yields a good straight line with the slope p = 1.06. These data suggest that the reaction proceeds by way of the chromic ester of hydrated benzaldehyde as intermediate, viz. 

Starting from the findings of the racemic cross-benzoin condensation [66], and assuming that aldehydes not accepted as donor substrates might still be suitable acceptor substrates, and vice versa, a mixed enzyme-substrate screening was performed in order to identify a biocatalytic system for the asymmetric cross-carboligation of aromatic aldehydes. For this purpose the reactions of 2-chloro-(40a), 2-methoxy- (40b) and 2-methylbenzaldehyde (40c), respectively, were studied with different enzymes in combination with benzaldehyde (Scheme 2.2.7.23) [67]. The three ortho-substituted benzaldehyde derivatives 40a-40c were... 

The usual method of synthesis of methoxy substituted benzaldehyde derivatives is by formylation of the methoxy substituted benzene derivatives. The formylation is generally effected by acid catalysed electrophilic substitution reactions like the Vils-meyer-Haack reaction. When resorcinol dimethylether is formylated under these conditions, the product obtained is the derivative (2) and not (7). 

A small group of isoquinoline alkaloids, in which substituted benzaldehyde derivatives such as 9 appear to be involved in the biosynthetic process, occurs in the genus Cryp-tostylis (Orchidaceae) (Fig. 32.4). Dopamine serves as a precursor for both aromatic rings of the system (Lundstrom, 1983). 

Benzoylformate decarboxylase (BFD) from P. putida (Table 10.4, entries 1-5) catalyzes the acyloin condensation of benzaldehyde or benzoyl formate derivatives to acetaldehyde, furnishing (S)-configured acyloins. BDF showed a preference for aromatic aldehydes as donors and aliphatic aldehydes as acceptors, although with lower reaction rates than BAL [14,55], The meta- and para-substituted benzaldehyde derivatives as well as heteroaromatic, olefinic, and cyclic aliphatic aldehydes are transformed with good to excellent conversions and enantioselectivities [14,55,56,63,64]... 

Reactions. Heating an aqueous solution of malonic acid above 70°C results in its decomposition to acetic acid and carbon dioxide. Malonic acid is a useful tool for synthesizing a-unsaturated carboxyUc acids because of its abiUty to undergo decarboxylation and condensation with aldehydes or ketones at the methylene group. Cinnamic acids are formed from the reaction of malonic acid and benzaldehyde derivatives (1). If aUphatic aldehydes are used acryhc acids result (2). Similarly this facile decarboxylation combined with the condensation with an activated double bond yields a-substituted acetic acid derivatives. For example, 4-thiazohdine acetic acids (2) are readily prepared from 2,5-dihydro-l,3-thiazoles (3). A further feature of malonic acid is that it does not form an anhydride when heated with phosphorous pentoxide [1314-56-3] but rather carbon suboxide [504-64-3] [0=C=C=0], a toxic gas that reacts with water to reform malonic acid. 

Sterically hindered derivatives of isoxazole carboxylic acids have yielded a goodly number of antibiotics. Chlorination of the oxime of the appropriately substituted benzaldehydes (15) leads to the intermediates, ( 16. Condensation of the chloro oximes with ethyl acetoacetate in base gives the esters (17) of the desired isoxazole carboxylic acids. Alternately, the esters... 

More recently, other substituted benzylidene derivatives of the enantiomers of a-methyl-benzylamine have been converted with substituted benzaldehydes to the corresponding phenyl-glycinonitriles using sodium cyanide in aqueous methanol44. 

Quinoxaline and acetaldehyde gave 2-acetylquinoxaline (Bu OaH, FeS04, H2SO4-H2O, 10°C, 50 min 78%) benzaldehyde similarly gave 2-benzoyl-quinoxaline (55%) " and several substituted benzoyl derivatives were made likewise. " (See also Section 7.7.1.)... 

Kovacs-Hadady and Kiss [27] studied the chromatographic characteristics of thia-zolidinecarboxylic acid derivatives, formed by reaction of (i>) and (L)-penicillamine with various substituted benzaldehydes and heterocyclic aldehydes in order to evaluate the aldehydes as derivatizing agents for separation of the penicillamine enantiomers. The TLC method of Martens et al. [28] was used. Transformation to thiazolidine carboxylic acids with benzaldehyde and substituted benzaldehydes was not complete, so formaldehyde is still the preferred reagent for separation of the enantiomers. 

Tab. 5.17 Benzylidene derivatives of 2-cineolylol from p-substituted benzaldehydes [27].

Three other substituted benzaldehydes, p-dimethylaminobenzaldchydc (130), julo-lidinecarboxaldehyde (131) and p-dimethylaminocinnamaldehyde (132), have been reported for use in the preparation of chromophoric derivatives of chiral amines116117. 

The rate of the base-catalysed condensation of carbonyl compounds with alkyl groups activated by Jt-deficient aromatic systems is enhanced by the addition of quaternary ammonium salts. For example, 2-methylbenzoxazole, 2-methylbenzo-thiazole and 4-nitrotoluene react with a range of substituted benzaldehydes to produce the corresponding 2-styryl derivatives (62-80%) at room temperature over 1 -2 hours [61, 62]. The intermediate alcohol can also be isolated after a short reaction time. 

A summary of representative stereochemically defined metal enolates and their respective kinetic aldol condensations with benzaldehyde is provided in Table 24. Both the metal center and the enolate substituent Ri for the substituted carbonyl derivatives... 

When benzene or its derivative is treated with carbon monoxide and hydrogen chloride In the presence of anhydrous aluminium chloride or cuprous chloride, it gives benzaldehyde or substituted benzaldehyde. 

Internal DCR of Nitroaldol Libraries (Scheme 6.10) [5,6] iDCR was demonstrated by using a conceptual nitroaldol library including five benzaldehyde derivatives (24,36, and 47-49) and one nitroalkane (50, DCL-F, Scheme 6.11). The benzaldehydes, all with a unique substitution pattern, were selected in order to make analysis clear and simple. However, one of the henzaldehydes contained a cyano functionality in the 2-position (49), deliberately making it a candidate for subsequent tandem cyclization following nitroalcohol formation. 5-exo-dig type cyclizations of hydrox-ynitriles to the corresponding iminolactones are expected [40,41], albeit unexplored [42 5], intramolecular transformations, which in this case could lead to possible kinetic resolution of the library. 

Several examples of Bi(0Tf)34H20-catalyzed Mannich-type reactions of various A-benzyloxycarbonylamino sulfones 1 with silyl enol ethers are summarized in Table 5. A-Benzyloxycarbonylamino sulfones 1 derived from differently substituted benzaldehydes were reacted with trimethyl(l-phenylvinyloxy)silane in dichloromethane at room temperature. The corresponding (3-amino ketones 24 were smoothly obtained (Table 5, entries 1-6). The reaction was efficient using electron-deficient benzaldehyde-derived sulfones, and the corresponding (3-amino ketones 24... 

The Schiff bases from substituted benzaldehydes and anilines will carbonylate in the presence of cobalt carbonyl, as catalyst at 225°C. producing phthalimidine derivatives, XVI, in good yield (70, 52). This reaction may be explained as an... 

In this section we generated an -value of by taking the family of identity exchange reactions of benzyl derivatives (109) (Pross, 1983). That particular -value is sufficiently anomalous to deter any possible application to questions of transition state structure. Yet there are cases that are, in principle, quite similar to the identity exchange reaction in which a-values are utilized as a measure of transition state structure. In such cases we believe the conclusions may not be valid. A typical example (Bell and Sorenson, 1976) is the addition of hydroxide ion to substituted benzaldehydes (110). For this system the sensitivity of rates and equilibria to substituent effects was similar. 

In organic solvents the acidity functions H corresponding to hydrogen dissociation from neutral indicator acids were reported for solutions of alkali metal alkoxides in various alcohols (2), using nitroanilines (21), aminobenzenecarboxylic acids (22), or indols (23) as indicators. For addition reactions of methoxide and ethoxide ions to neutral indicator acids, acidity functions J (also denoted as Hr) based on use of nitrobenzenes (21) and a-cyanostilbenes (18) as indicators in methanol and dimethylsulfoxide-methanol and -ethanol mixtures were reported. Recently (24) the acidity function J- (denoted as Jm) was derived for methoxide ion solutions in methanol using substituted benzaldehydes as indicators. These scales involve arbitrary choice of water as the solvent for determination of the dissociation constant of the anchoring acid. 

The xanthene dyes may be classified into two main groups diphenyl-methane derivatives, called pyronines. and triphenylmethane derivatives (e.g.. (3)). which are mainly phthaleins made from phthalic anhydride condensations. A third much smaller group of rosamines (9-phenylxanthenes) is prepared from substituted benzaldehydes. The phthaleins may be further subdivided into the following fluoresceins (hydroxy substituted) Rho-damines (amino substituted), e.g.. (4) and mixed hydroxy/amino substituted. 

Rosamines. Rosamines are 9-phenylxanthene derivatives prepared front substituted benzaldehydes instead of phthalic anhydride. Sulforhodamine B (Acid Red 52 Cl 45100) is the most important rosamine. 

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