Benzaldehyde preparation

A one-pot synthesis of thiohydantoins has been developed using microwave heating [72]. A small subset of p-substituted benzaldehydes, prepared in situ from p-bromobenzaldehyde by microwave-assisted Suzuki or Negishi reactions, was reacted in one pot by reductive amination followed by cyclization with a thioisocyanate catalyzed by polystyrene-bound dimethyl-aminopyridine (PS-DMAP) or triethylamine, all carried out under microwave irradiation, to give the thiohydantoin products in up to 68% isolated yield (Scheme 16). 

One of the earliest perfumery materials to be produced industrially was benzaldehyde, prepared from toluene in 1866. In 1868 coumarin was first synthesized, soon to be followed by heliotropin, ionone, and vanillin. The first nitro musks appeared in 1888, and amyl salicylate in 1898. Since then, for the last hundred years, the history of perfumery has been dominated by the creation of new aromatic chemicals. 

The ionic liquid grafted benzaldehydes prepared for the 1,3-dipolar cydoaddition reactions have also been used successfully as substrates for Knoevenagel reactions using microwave irradiation (Scheme 7.16). One equivalent of different malonate derivatives with a variety of electron-withdrawing groups was added to the ionic liquid phase and piperidine was used as catalyst. Reaction times varied from 15-60 min. The product was cleaved from the ionic liquid phase by using the NaOMe... 

Methyltriphenylphosphonium bromide (389 g) and 126 g of potassium t-butoxide were added to 2 L of freshly distilled tetrahydrofuran (THIO under nitrogen protection. After 30 minutes of stirring, a solution of 160 g of 4-(l-methoi etho )benzaldehyde prepared as above in 300 mL THF was added slowly. The reaction was stirred at room temperature overnight. Crashed ice (1 kg) was added to the reaction mixture with stirring. After two phases were separated, the aqueous layer was extracted with eth acetate twice. The combined organic phases were dried over meganesium sulfate and the solvents were removed under reduced pressure. The product was a colorless liquid, whidi was... 

It is used for the preparation of benzaldehyde. For (his purpose it is usually heated with slaked lime and water under pressure. 

Usually prepared by the action of NaCN on benzaldehyde in dilute alcohol. It is oxidized by nitric acid to benzil, and reduced by sodium amalgam to hydrobenzoin PhCHOHCHOHPh by tin amalgam and hydrochloric acid to des-oxybenzoin, PhCH2COPh and by zinc amalgam to stilbene PhCH = CHPh. It gives an oxime, phenylhydrazone and ethanoyl derivative. The a-oxime is used under the name cupron for the estimation of copper and molybdenum. 

Prepared by healing benzaldehyde with sodium ethanoate and ethanoic anhydride (Perkin reaction) or with ethyl ethanoate and sodium ethoxide. Occurs in storax, or liquid... 

C. Insoluble in water, soluble in organic solvents. Flavone occurs naturally as dust on the flowers and leaves of primulas. It has been prepared from o-hydroxyacetophenone and benzaldehyde. 

Nitrobenzene is a pale yellow liquid, having a b.p. 210 , and dy 1 20. It has an odour which is similar to that of almonds, and which is therefore often confused with that of benzaldehyde. Nitrobenzene is used chiefly for the preparation of aniline. 

Cinnamic acid is usually prepared by Perkin s reaction, benzaldehyde being heated with sodium acetate in the presence of acetic anhydride. It is probable that the benzaldehyde and the acetic anhydride combine under the catalytic action of the sodium acetate, and the product then readily loses water to give mono-benzylidene acetic anhydride (. ). The latter, when subsequently... 

Preparation of REAOENTS.t It is essential for this preparation that the zinc powder should be in an active condition. For this purpose, it is usually sufficient if a sample of ordinary technical zinc powder is vigorously shaken in a flask with pure ether, and then filtered off at the pump, washed once with ether, quickly drained and without delay transferred to a vacuum desiccator. If, however, an impure sample of zinc dust fails to respond to this treatment, it should be vigorously stirred in a beaker with 5% aqueous sodium hydroxide solution until an effervescence of hydrogen occurs, and then filtered at the pump, washed thoroughly with distilled water, and then rapidly with ethanol and ether, and dried as before in a vacuum desiccator. The ethyl bromoacetate (b.p. 159 ) and the benzaldehyde (b.p. 179 ) should be dried and distilled before use. 

Here the phenylacetic anhydride, possessing more reactive a-hydrogen atoms, condenses with benzaldehyde to give a-phenylcinnamic acid. The preparation of the latter is an example of the Oglialoro modiflcation of the Perkin reaction. 

The preparation of a-phenylclnnamlc acid from benzaldehyde, phenylacetic acid, acetic anhydride and triethylamine is described. Presumably equilibria are set up between phenylacetic acid and acetic anhydride to form phenylacetic anhydride, a mixed anhydride or both ... 

In a 500 ml. wide-mouthed reagent bottle place a cold solution of 25 g. of sodium hydroxide in 250 ml. of water and 200 ml. of alcohol (1) equip the bottle with a mechanical stirrer and surround it with a bath of water. Maintain the temperature of the solution at 20-25°, stir vigorously and add one-half of a previously prepared mixture of 26-5 g. (25 -5 ml.) of purebenzaldehyde (Section IV,115) and 7 -3 g. (9-3 ml.) of A.R. acetone. A flocculent precipitate forms in 2-3 minutes. After 15 minutes add the remainder of the benzaldehyde - acetone mixture. Continue the stirring for a further 30 minutes. Filter at the pump and wash with cold water to eliminate the alkali as completely as possible. Dry the solid at room temperature upon filter paper to constant weight 27 g. of crude dibenzalacetone, m.p. 105-107°, are obtained. Recrystallise from hot ethyl acetate (2-5 ml. per gram) or from hot rectified spirit. The recovery of pure dibenzalacetone, m.p. 112°, is about 80 per cent. 

Azines, Aldehydes react with hydrazine to yield azines the reaction cannot usually be arrested at the hydrazone stage. This reaction may be illustrated by the preparation of bevzalazine from benzaldehyde ... 

Benzyl alcohol. This alcohol, b.p. 205-5°, may be similarly prepared from benzaldehyde in approximately the same yield (compare Section IV, 123.)... 

Atophan (or cihchophen) may be prepared by condensing equimolecular proportions of benzaldehyde, aniline and pyruvic acid in alcoholic solution ... 

The synthesis of 3-phenyl-]-(2-pyridyl)-2-propen-]-one (2.4c) via an aldol reaction of 2-acetylpyridine with benzaldehyde has been described in the literature ". O jmpound 2.4a-e have been prepared in high yields, using slightly modified versions of these literature procedures. 

The higjily water-soluble dienophiles 2.4f and2.4g have been synthesised as outlined in Scheme 2.5. Both compounds were prepared from p-(bromomethyl)benzaldehyde (2.8) which was synthesised by reducing p-(bromomethyl)benzonitrile (2.7) with diisobutyl aluminium hydride following a literature procedure2.4f was obtained in two steps by conversion of 2.8 to the corresponding sodium sulfonate (2.9), followed by an aldol reaction with 2-acetylpyridine. In the preparation of 2.4g the sequence of steps had to be reversed Here, the aldol condensation of 2.8 with 2-acetylpyridine was followed by nucleophilic substitution of the bromide of 2.10 by trimethylamine. Attempts to prepare 2.4f from 2.10 by treatment with sodium sulfite failed, due to decomposition of 2.10 under the conditions required for the substitution by sulfite anion. 

Ni(N03)2 6H20, Cu(N03)2 3H20, Zn(N03)2-4H20 and KNOj were of the highest purity available. Substituted 3-phenyl-l-(2-pyridyl)-2-propene-ones (2.4a-e) were prepared by an aldol condensation of the corresponding substituted benzaldehyde with 2-acetylpyridine, following either of two modified... 

After the air in the flask had been completely replaced with nitrogen, it was cooled in a liquid nitrogen bath and a solution of 25 g of acetylene in 160 ml of dry THF was introduced. The solution had been prepared by dissolving acetylene (freed from acetone by means of a cold trap) in THF cooled at -80 to -90°C. A solution of 0.21 mol of butyl lithium in about 150 ml of hexane was added in 5 min to the vigorously stirred solution. During this addition the temperature of the mixture was kept between -80 and -100°C by occasionally dipping the flask into the liquid nitrogen. To the white suspension were successively added at -80°C a solution of 10 g. of anhydrous lithium bromide (note 1) in 30 ml of THF and 0.20 mol of freshly distilled benzaldehyde. The reaction mixture was kept for 3 h at -69°C, after which the temperature was allowed to rise to +10°C over a period of 2 h. 

Aldehydes can also be prepared by the carbonylation of aryl and alkenyl halides and triflate, and benzyl and allyl chlorides using tin hydride as a hydride source and Pd(PhjP)4 as a catalyst[377]. Hydrosilancs arc used as another hydride source[378]. The arenediazonium tetralluoroborate 515 is converted into a benzaldehyde derivative rapidly in a good yield by using Et ,SiH or PH MS as the hydride source[379]. 

Furthermore, they react with carbonyl derivatives such as acetone and benzaldehyde to give selenohydrazones identical to those prepared from the condensation of selenosemicarbazones with an a-halocarbonyl compound. 

Substituted 5-hydroxythiazoles (267b), Rj = alkylmercapto, acyl-amino, and sec-amino, are prepared by cydization of N-thioacyl-amino acids (266) with phosphorus tribromide or acetic anhydride (Scheme 137) (317, 350). i en the cydization of 266, R2 = H, is carried out with acetic anhydride in the presence of benzaldehyde (317, 325) or ethylformate (317), the benzylidene (268), R2=Ph, Rj = SR or CH2Ph, or 4-ethoxymethylene (268), Rj = SR and R2 = OEt, derivative is obtained directly (Scheme 138). 

The same products can be also obtained from 267 and benzaldehyde. This behavior indicates the presence of an active methylene group and supports the thiazolone structure (267a). Alkyl or aryl ethers of 267 are prepared by two different procedures (Scheme 139). 

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