Benzaldehyde, oxidation chromatography

Benzoic acid has long been considered to be formed by benzaldehyde oxidation in the presence of oxygen, but was not bebeved to form under anaerobic conditions [95]. Here, when the reaction was performed under anaerobic conditions, benzoic acid was not detected in the effluent by gas chromatography (GC) analysis, but in situ ATR-IR spectra clearly showed its presence as an adsorbed benzoate species, indicated by bands at 1600, 1546,1422, and 1393 cm [94]. The fact that benzoate species are detected on the catalyst surface, but not in the effluent, suggests that these species are very strongly bound possibly at basic sites on the AljOj support The formation of benzoic acid/benzoate under anaerobic conditions was speculated to result from hydration of benzaldehyde via a germinal diol, followed by a dehydrogenation. This pathway is summarized as follows ... 

LDA (0.118 g, 1.1 mmol) was added to (SP)-f-butyl(phenyl)phosphine oxide (0.182 g, 1 mmol) in tetrahydrofuran (5 ml) under an atmosphere of nitrogen at -78°C. After 15 min, the solution was treated with a solution of benzaldehyde (0.117 g, 1.1 mol) in tetrahydrofuran (2 ml), and the resultant mixture was stirred at -78°C for 3 h. Evaporation of the solvent and flash chromatography of the residue provided the (SP)-f-butyl(phenyl)(a-hydroxybenzyl)phosphine oxide (0.22 g, 77%) with a diastereoisomeric ratio of 98 2, which exhibited spectral data in accord with the proposed structure. 

The imidazolidine-4-one 29, obtained by heating the methanol solution of an a-aminoamide and a 4-substituted benzaldehyde, is a mixture of two diastereomers which can be separated by chromatography. They are oxidized by MCPBA, separately or as a mixture, into the two diastereomeric l-hydroxyimidazolidine-4-ones 30. Hydrolysis of 30 by ethanolic HC1 and hydroxylamine hydrochloride gives the optically pure TV-hydroxyamino acid amide 31 (Scheme 9).[12]... 

The oxidation of benzyl alcohol la to benzaldehyde 2a is representative of the general procedure employed. Benzyl alcohol la (0.108 g, 1 mmol) and IBD (0.355 g, 1.1 mmol) doped on neutral alumina (1 g) are mixed thoroughly on a vortex mixer. The reaction mixture is placed in an alumina bath inside an unmodified household microwave oven and irradiated for a period of 1 min. On completion of the reaction, followed by TLC examination (hexane-AcOEt, 9 1, v/v), the product is extracted into dichloromethane and is neutralized with aqueous sodium bicarbonate solution. The dichloromethane layer is separated, dried over magnesium sulfate, filtered, and the crude product thus obtained is purified by column chromatography to afford pure benzaldehyde 2a in 94% yield. Alternatively, the crude products are charged on a silica gel column that provides io-dobenzene on elution with hexane followed by pure carbonyl compounds in solvent system (hexane-ethyl acetate, 9 1, v/v). 

The incorporation of the second equivalent of imine can be prevented in these reactions if a vinylidene complex, such as (31), is employed which is 3optimized conditions indicated, the reaction of (31) with A -meAyl benzaldehyde imine will provide the cycloadduct (32) in quite good yield. A rather unc odox oxidation procedure (BU4NNO2, 6.5 kbar 1 bar = 10 Pa) is required for the effective cleavage of the cationic complex (32) to the 3-lactam (33). This reaction was shown to involve a two-step process, since the salt (37) could be isolated in 80% yield by column chromatography if the reaction was stO[q)ed shortly after the reaction mixture was Ivought to room tenq>erature. The reaction with the cyclic thioimidate (34) indicates that vinylidene complexes can be useful in the synthesis of functionalized 3-lactams in good yields with high stereoselectivity. 

The toluene oxidation reaction was used as a probe to study the catalytic properties of the Mo-Ce complex oxides. The as-prepared oxides were introduced into a U-type quartz fixed bed microreactor and their catalytic properties for selective oxidation of toluene to benzaldehyde were evaluated under the reaction conditions of O.lMPa, 400 C, air/toluene = 9 (vol/vol), F/W =1900 ml/h g cat. The reaction products were analyzed by an on-line gas chromatography. Under the above reaction conditions, the main products were CO, CO2, H2O and benzaldehyde. 

The phosphonium salt was subjected to a Wittig reaction with a dimethylformamide solution of 212 mg (2 mmol) of benzaldehyde and sodium methoxide as a base. The solution was heated at about 80 °C and stirred for 8 h. After cooling, water was added and the mixture extracted with toluene. The combined extracts were washed with water, dried over MgS04 and the solvent evaporated. After column chromatography of the residue on aluminium oxide with CCI4 as the eluant the cw-isomer of 2-styrylbenzo[c]phenanthrene was isolated, whereas the traiw-isomer was obtained after elution with a mixture of hexane and toluene (1 5). The overall yield was 65% (mp cis. 142 - 144 °C, mp trans-. 224 - 226 °C). 

Warren showed that olefination of ketones and aldehydes, or even esters, with phosphine oxide carbanions allows some control of stereochemistry in the alkene products. Reaction with an aldehyde or ketone generates diastereomeric P-hydroxyphosphine oxide products, which can be isolated and then chromatographically separated. Reaction of 573 with n-butyllithium was followed by addition of 3,4-methylenedioxy-benzaldehyde (574, known as piperonal) to give a 9 1 mixture of 575/576, the syn and anti alcohol, respectively.514 7i,e pyre syn alcohol 575 was isolated in 75% yield by chromatography on silica gel. 

Recently, we also observed abnormal deuterium distribution of a sample of benzaldehyde, which deviated significantly from the expected cluster formed by benzaldehydes produced from cinnamic aldehyde. Adulteration and use of a starting material from an unknown source were ruled out. Experiment results indicated that the deuterium shift was not due to oxidation and isotope exchange. No chromatography process was used. Our attention focused on tlie distillation process. 

A solution of [Cu (L )(NEt3)] in THE can stoichiometrically convert benzyl and ethyl alcohol to benzaldehyde and ethanal, respectively, under anaerobic conditions at room temperatru e. These oxidation reactions can be performed in open air with catalytic amounts of [Cu (L )(NEt3)]. Thus, 2.65 x 10 M catalyst in THE could oxidize a 0.125 M ethanol or benzyl alcohol solution (55 % yield, 2594 TON) within 20 hours reaction time, at room temperature under air. The catalytic reactions could be carried out without solvent, and no over-oxidation products or oxidative C C coupling compounds could be detected by gas chromatography, which is a significant improvement of the catalytic system described above (see Table V). 

Carbon telrabromide (26.1 g, 78.6 mmol) was added portionwise to a solution of triphenylphosphine (41.3 g, 158 mmol) in CH2CI2 (300 mL), and the resultant deep red solution stirred at rt. for 15 min. Benzaldehyde (2.00 mL, 19.7 mmol) was then added dropwise at 0 °C, and the mixture stirred at rt. for 2 h. Pentane (200 mL) was added to the mixture, and the precipitated triphenylphosphine oxide removed by filtration through a pad of siUca. The filtrate was concentrated under reduced pressure, and the residue purified by column chromatography (petrol) to afford (2,2-dibromovinyl)benzene (2.79 g, 54 %) as a pale yellow oil. 

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