Hydroxylated benzaldehydes

An assay method for benzaldehyde involves condensing benzaldehyde with hydroxyl amine hydrochloride to form an oxime. The released hydrochloric acid is then titrated. 

Pyrolytic Decomposition. The pyrolytic decomposition at 350—460°C of castor oil or the methyl ester of ricinoleic acid spHts the ricinoleate molecule at the hydroxyl group forming heptaldehyde and undecylenic acids. Heptaldehyde, used in the manufacture of synthetic flavors and fragrances (see Elavors and spices Perfumes) may also be converted to heptanoic acid by various oxidation techniques and to heptyl alcohol by catalytic hydrogenation. When heptaldehyde reacts with benzaldehyde, amyl cinnamic aldehyde is produced (see Cinnamic acid, cinnamaldehyde, and cinnamyl... 

A method of fixing the position of the double bond involves first condensing the 20-ketopregnane with benzaldehyde at C-21, then reducing the ketone to hydroxyl and dehydrating.Alternatively, the 20-keto-21-benzylidene steroid can be converted to the A ° -enol chloride prior to ozonolysis. 

One of the earliest preparations of this ring system starts with displacement of the hydroxyl of benzaldehyde cyanohydrin (125) by urea. Treatment of the product (126) with hydrochloric acid leads to addition of the remaining urea nitrogen to the nitrile. There is thus obtained, after hydrolysis of the imine (127), the hydantoin (128). Alkylation by means of ethyl iodide affords ethotoin (129)... 

The anion produced by VNS of nitroarenes andct-chloro esters is hydroxylated by the ac of air and benzaldehyde, thereby producing ct-hydroxy esters fEq 9 37,... 

Benzaldehyde cyanohydrin is reacted with urea to displace the hydroxyl group of the cyanohydrin. That intermediate is treated with HCI to convert the urea nitrogen to a nitrile. The resultant imine is hydrolyzed to the phenylhydantoin. Alkylation with ethyl iodide gives ethotoin, as described by A. Pinner in Chem. Ber. 21, 2325 (1888). 

The synthesis of the right-wing sector, compound 4, commences with the prochiral diol 26 (see Scheme 4). The latter substance is known and can be conveniently prepared in two steps from diethyl malonate via C-allylation, followed by reduction of the two ethoxy-carbonyl functions. Exposure of 26 to benzaldehyde and a catalytic amount of camphorsulfonic acid (CSA) under dehydrating conditions accomplishes the simultaneous protection of both hydroxyl groups in the form of a benzylidene acetal (see intermediate 32, Scheme 4). Interestingly, when benzylidene acetal 32 is treated with lithium aluminum hydride and aluminum trichloride (1 4) in ether at 25 °C, a Lewis acid induced reduction takes place to give... 

Optically active Art-butyl 2-(4-methylphenylsulfinyl)propanoate only reacted with aldehydes in the presence of e//-butylmagnesium bromide as a base36. The asymmetric induction for the formation of the hydroxylic center was higher in the case of aliphatic aldehydes (75-80%) than in the case of benzaldehyde (33%). The diastereoselectivity regarding the tertiary center to sulfur was not determined. 

Hydroxyl elimination is necessary for the formation of benzaldehyde and benzoic acid derivatives and, ultimately, benzene and toluene (Fig. 7.46).2 It is proposed that a cleavage between the hydroxyl group and aromatic ring leads to benzenoid species which undergo further cleavage coupled with oxidation to give various decomposition products. 

Typical non-enolising aldehydes are formaldehyde and benzaldehyde, which are oxidised by Co(III) Ce(IV) perchlorate and sulphate , and Mn(III) . The main kinetic features and the primary kinetic isotope effects are the same as for the analogous cyclohexanol oxidations (section 4.3.5) and it is highly probable that the same general mechanism operates. kif olko20 for Co(III) oxidation of formaldehyde is 1.81 (ref. 141), a value in agreement with the observed acid-retardation, i.e. not in accordance with abstraction of a hydroxylic hydrogen atom from H2C(OH)2-The V(V) perchlorate oxidations of formaldehyde and chloral hydrate display an unusual rate expression, viz. 

The hydroxyl groups of aldonolactones react with a variety of aldehydes and ketones to give the corresponding acetal derivatives. Treatment of the salts of aldonic acids with benzaldehyde and hydrochloric acid or zinc chloride as catalysts give benzylidene derivatives of aldonic acids or aldonolactones (3). 

Much emphasis has been placed on the selectivity of quaternary ammonium borohydrides in their reduction of aldehydes and ketones [18-20]. Predictably, steric factors are important, as are mesomeric electronic effects in the case of 4-substituted benzaldehydes. However, comparison of the relative merits of the use of tetraethyl-ammonium, or tetra-n-butylammonium borohydride in dichloromethane, and of sodium borohydride in isopropanol, has shown that, in the competitive reduction of benzaldehyde and acetophenone, each system preferentially reduces the aldehyde and that the ratio of benzyl alcohol to 1-phenylethanol is invariably ca. 4 1 [18-20], Thus, the only advantage in the use of the ammonium salts would appear to facilitate the use of non-hydroxylic solvents. In all reductions, the use of the more lipophilic tetra-n-butylammonium salt is to be preferred and the only advantage in using the tetraethylammonium salt is its ready removal from the reaction mixture by dissolution in water. 

Note that a six-membered ketal ring involving the hydroxyls at 4 and 6 is not favoured this is because such a ring would necessarily force one of the two methyls into an axial position. On the other hand, these two hydroxyls can be employed in forming a cyclic acetal with benzaldehyde. Benzaldehyde shows a tendency to form six-membered ring acetals, and because the two substituents are phenyl and hydrogen, we can have a favourable chair system with the phenyl equatorial. 

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