Aldehyde from benzene

Aromatic Aldehydes. The preparation of aromatic aldehydes from benzene or monoalkyl and polyalkyl aromatic compounds by means of carbon monoxide and hydrogen chloride has been reviewed by Crounse (19). 

A ketone can also be formed with a Friedel-Crafts acylation. The process requires an acid chloride and an aromatic compound. An aldehyde can t be formed by this procedure because the appropriate acid chloride, formyl chloride (HCOCl), is unstable and decomposes to carbon monoxide and hydrogen chloride. Figure 10-12 illustrates the preparation of acetophenone from benzene and acetyl chloride. 

Direct electrophilic substitution of benz- and dibenz-azepines remains relatively unexplored. Most substituted benzazepines have been prepared from benzene precursors bearing the desired substituents (74AHC(17)45). The bulk of the reported electrophilic substitutions have been carried out on 5//-dibenz[6,/]azepine (74CRV101), MO calculations on which predict that substitution should occur at the 2- and 4-positions, i.e. para and ortho to the azepine ring nitrogen. These predictions are borne out by Friedel-Crafts alkylation and acylation studies, although it is apparent that a second alkyl group enters at the 8- rather than at the 4-position. Formylation under Vilsmeier conditions yields the 2-aldehyde. As noted earlier (Section 5.16.3.4), however, the 10,11-dihydro system exhibits different behavior and acylates at the benzylic 10,11-positions. Nitration with mixed acids of the... 

The activity and selectivity of 19 oxides at 400—450°C were investigated by Germain and Laugier [133], The activities are compared with those for the oxidation of toluene in Fig. 8, and show a linear relationship for the major part of the oxides, the toluene oxidation being approximately twice as fast as the benzene oxidation. The only selective catalysts, i.e. those that produce substantial amounts of benzoquinone and maleic anhydride from benzene, and benzaldehyde and benzoic acid from toluene are the oxides of V, Mo and W. Remarkably, these oxides clearly deviate from the average correlation in Fig. 8 and show a much higher tol-uene/benzene activity ratio (about 10/1). The order of activity, maximum yield of maleic aldehyde and initial selectivity with respect to benzoquinone is the same for these oxides V > Mo > W. 

The substituted benzyl alcohols listed below are prepared in a similar manner from the corresponding aldehydes in the yield indicated vanillyl alcohol, m.p. 113-114°, recrystallized from benzene, 95% anisyl alcohol, b.p. 127-130°/8 mm., 92% piperonyl alcohol, m.p. 52-53°, recrystallized from a mixture of ether and petroleum ether, 91% p-chlorobenzyl alcohol, m.p. 71-72.5°, recrystallized from ben-zene-ligroin mixture, 92% o-chlorobenzyl alcohol, m.p. 64 -65°, 96% p-bromobenzyl alcohol, m.p. 76-76.5°, 96%. 

This is the simplest case of the reaction but it has been mostly used in the synthesis of higher members of the unsaturated acid series, e.g., the nine carbon acid, nonylenic acid, which is prepared from the seven carbon aldehyde known as oenanthylic aldehyde, or oenanthol, obtained from castor oil. Even more important than its application in the synthesis of higher acids of the ethylene series is the use of the reaction in the synthesis of aromatic unsaturated cLcids derived from benzene and containing an unsaturated side chain (see cinnamic acid. Part II). The reaction is known as the Perkin Synthesis or as the Perkin-Fittig Synthesis from the men who suggested and explained it. 

TO-hydroxybenzaldehyde. The aldehyde dissolves slowly, and the mixture becomes warm the mixture is>wibmed to 50-60°, and rapid solution of the aldehyde takes place. After one hour at 50-60° the solution is acidified with dilute hydrochloric add, saturated with sodium bicarbonate, and extracted with ether. From the ether solution is obtained 5.8 g. (93.6%) of m-hydroxybenzyl alcohol, m.p. 68° after one recrystallization from benzene the m.p. is 73° (corr.). 

Triazolines with secondary or tertiary amino groups in the 4 position were similarly made by treating a primary or secondary amine (respectively) with an aldehyde or ketone and p-nitrophenyl azide in chloroform (25°C, 1-14 hr, 30-98%) (64JA2213 69G1131). The products isolated from chloroform were usually mixtures of cis and trans isomers [as determined by NMR (See Section II,D)], whereas recrystallization from benzene gave the pure trans isomer, which was conformationally stable only if a bulky group, such as phenyl, occupied the 5 position [72JCS(P1)997]. 

A notable recent innovation is the coupling of dimethyl acetylenedicarboxylate (DMAD), cyclohexyl isocyanide and an aromatic aldehyde in benzene under reflux giving the 2-aminofurans 70 in good yield (60 70%) (Eq. (9)) (00CC1019, 03ACR899). The method can be carried out at room temperature in higher yield in an ionic liquid (l-butyl-3-methylimidazolium tetrafluoroborate) from which the product is easily isolated by extraction with ether (04S2376). 

Scheme 4.52 shows the preparation of the hydrocinnamic aldehydes, another family of materials derived from benzene and which possess fresh, white-floral notes reminiscent of muguet (lily of the valley) and cyclamen. One of these, Lilial or Lilistralis , can also be prepared from toluene, and that route is also described in this section for... 

Although little experimental data is available, numerous patents have been issued for the vapor phase catalytic oxidation of various other derivatives containing the benzene nucleus, as well as heterocyclic compounds Thus, fluorene (diphenyl methane) is oxidized to fluorenone with air in the presence of a catalyst containing iron vanadate or other suitable metal salt of the fifth or sixth group of the periodic system at a temperature of 360° to 400°.1,2 Maleic acid and anhydride are formed by the catalytic oxidation of compounds of the furan series, such as furan, furfural alcohol, furfural, methyl furfural, hydroxymethylfurfural, pyromucic acid or mixtures, with air over catalysts of molybdenum, vanadium, or other metals.133 Dimethyl benzaldehyde is formed by oxidizing pseudocumene with air at 550° C. in the presence of a tungsten oxide catalyst. Molybdenum, vanadium, or tantalum oxide catalysts may also be used to form aromatic aldehydes from o-, m-, or p-xylenes, mesitylene, p-cymene, or o-chlorotoluene by air oxidation. Times of contact of 0.3 to 0.4 seconds... 

It is true that, for instance, one does not find under the keyword aldehyde the preparation of benzaldehyde (a) from toluene by way of benzyl chloride or benzaldehyde dichloride, (b) from benzene and hydrogen cyanide-hydrogen chloride (Gattermann-Koch) or from bromobenzene by way of phenyl-magnesium bromide and formic ester (Grignard), and (c) from stilbene and ozone or from 1,2-diphenyl-1,2-ethanediol and lead tetraacetate but such a collection of syntheses is to be found in the systematic textbooks and reference works of organic chemistry, and the compass of the large reactions remains nevertheless substantially intact in our treatment. 

Pi- and Tetrahydrothiophens. - Condensation of mercaptoacet-aldehyde (from 2,5-dihydroxy-1,4-dithiane) with prenal, using potassium carbonate in benzene, gave (236) in 44% yield. Oxidation of (236) with active 2 gave (237), and by addition of Grignard... 

Benzene derivatives as such do not absorb much light in the solar UV region however, in the presence of oxygen some of them form complexes (Chien, 1965 Khalil and Kasha, 1978 Onodera et al., 1980 Pasternak and Morduchowitz, 1983) that are susceptible to photolysis. It appears that the absorption spectra of the complexes tail into the solar UV region (Chien, 1965) and that the quantum yield for reaction is rather high. Products of the reactions include long-chain conjugated dialdehydes from benzene itself (Wei et al., 1967) and alcohols and aldehydes from side-chain oxidation of alkyl-substituted benzenes (Pasternak and Morduchowitz,... 

Dimethylandrostane-6a,17/ -diol refluxed 2 hrs. in a dry suspension of excess Ag-carbonate-on-Celite in benzene 4,4-dimethyl-17-ketoandrostan-6a-ol. Y 87.5%. - Sterically hindered hydroxyl groups are not oxidized. F. e., also aldehydes from prim, alcohols, s. M. Fetizon and M. Golfier, C. r. 267 (C), 900 (1968) Chem. Commun. 1969, 1102. 

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