Chromium Diacetate

SYNS ACETIC ACID, CHROMIUiM (2+) SALT (SCI, 9CI) CHROMIUiM(2+) ACETATE CHROMIUM(II) ACETATE CHROMIUM DIACETATE CHROMOUS ACETATE CHROMOUS ACETATE MONOHYDRATE... 

Equip a I litre three-necked flask with a mechanical stirrer and a thermometer, and immerse the flask in a bath of ice and salt. Place 306 g. (283 ml.) of acetic anhydride, 300 g. (285 ml.) of glacial acetic acid and 25 g. of p-nitrotoluene in the flask, and add slowly, with stirring, 42 5 ml. of concentrated sulphuric acid. When the temperature has fallen to 5°, introduce 50 g. of A.R. chromic anhydride in small portions at such a rate that the temperature does not rise above 10° continue the stirring for 10 minutes after all the chromium trioxide has been added. Pour the contents of the flask into a 3 litre beaker two-thirds filled with crushed ice and almost fill the beaker with cold water. Filter the solid at the pump and wash it with cold water until the washings are colourless. Suspend the product in 250 ml. of cold 2 per cent, sodium carbonate solution and stir mechanically for 10-15 minutes filter (1), wash with cold water, and finally with 10 ml. of alcohol. Dry in a vacuum desiccator the yield of crude p-nitrobenzal diacetate is 26 g. (2),... 

The residue (12 g) which contains the 18-iodo-18,20-ether is dissolved in 200 ml of acetone, 5 g of silver chromate is added Note 3) and after cooling to 0°, 11.8 ml of a solution of 13.3 g of chromium trioxide and 11.5 ml of concentrated sulfuric acid, diluted to 50 ml with water is added during a period of 5 min. After an additional 60 min, a solution of 112 g of sodium acetate in 200 ml of water is added and the mixture diluted with benzene (400 ml), filtered and the benzene layer separated. The aqueous phase is reextracted with benzene, washed with half-saturated sodium chloride solution, dried and evaporated to yield 11.2 g of a crystalline residue. Recrystallization from ether gives 7.2 g (72%) of pure 3/5, 1 la, 20/5-trihydroxy-5a-pregnan-18-oic acid 18,20 lactone 3,11-diacetate mp 216-218°. 

Tricarbonyl( 1 -ewrfo-allyltetralin)chromium, stereoselective alcohol to hydrocarbon reduction, 132 1,2,3-Trideoxy-D-r/fco-hex-1 -enopyranose diacetate, allyl ester reduction,... 

The methyl substituent of 2-methyl-4,8-dihydrobenzo[l,2- 5,4-. ]dithiophene-4,8-dione 118 undergoes a number of synthetic transformations (Scheme 8), and is therefore a key intermediate for the preparation of a range of anthraquinone derivatives <1999BMC1025>. Thus, oxidation of 118 with chromium trioxide in acetic anhydride at low temperatures affords the diacetate intermediate 119 which is hydrolyzed with dilute sulfuric acid to yield the aldehyde 120. Direct oxidation of 118 to the carboxylic acid 121 proceeded in very low yield however, it can be produced efficiently by oxidation of aldehyde 120 using silver nitrate in dioxane. Reduction of aldehyde 120 with sodium borohydride in methanol gives a 90% yield of 2-hydroxymethyl derivative 122 which reacts with acetyl chloride or thionyl chloride to produce the 2-acetoxymethyl- and 2-chloromethyl-4,8-dihydrobenzo[l,2-A5,4-3 ]-dithiophene-4,8-diones 123 and 124, respectively. 

Several procedures for the synthesis of aromatic aldehydes are available which involve the selective oxidation of a methyl group attached to an aromatic ring. A useful general reagent is a solution of chromium trioxide in acetic anhydride and acetic acid. The aldehyde is converted into the gem-diacetate as it is formed and is thus protected from further oxidation. The aldehyde is liberated from the diacetate by hydrolysis under acid conditions the yields, however, are frequently only moderate (e.g. p-nitrobenzaldehyde, Expt 6.117). 

The identity of various derivatives is established by periodate titrations (41). Hydrolysis of the acetonide diacetate 6 by sulfuric acid in the presence of 2,4-dinitrophenylhydrazine (DNP) gives a small yield of the 16-acetate 10 (/). Also typical of the series, but not shown in the schemes, the C-7 alcohol group of compound 6 is oxidized to a ketone by chromium trioxide in pyridine (48,49). 

USA Inc., Cleveland, Ohio (11) chromium hydroxy diacetate McGean-Rohco, Inc., Cleveland, Ohio (12) chromium naphthenate OM Group, Inc., Franklin, Pennsylvania (13) chromium nitrate The Hall Chemical Co., Arab, Alabama McGean-Rohco, Inc., Cleveland, Ohio The Shepard Chemical Company, Cincinnati, Ohio (14) chromium octoate Dixie Chemical Company, Inc., Bayport, Texas ... 

Cognate preparations. o-Nitrobenzaldehyde. Use 25 g (0.18 mol) of o-nitrotoluene and proceed as for p-nitrobenzaldehyde, but allow a period of 3 hours stirring at 5-10 °C after the addition of the chromium trioxide solution. In the work-up, omit the final ethanol washing to remove unchanged o-nitrotoluene boil the crude product under reflux for 30 minutes with 120 ml of light petroleum (b.p. 60-80 °C). The yield of o-nitrobenzylidene diacetate of m.p. 82-84°C is 16 g (36%). 

Benzaldehyde is prepared by the hydrolysis of (dichloromethyl)benzene (benzal chloride) in either aqueous acid or aqueous alkali and by the oxidation of toluene with chromium trioxide in acetic anhydride (Scheme 6.3). In the latter synthesis, as the benzaldehyde is formed, it is converted into its diacetate by the acetic anhydride, so preventing further oxidation subsequent hydrolysis generates the aldehyde group. The benzaldehyde has thus been protected from oxidation. Benzyl alcohol can... 

Oxidation of the methyl group in substituted toluenes with chromium trioxide in acetic anhydride forms crystalline diacetates, which are stable to further oxidation. These compounds are readily hydrol)rzed in acid solution to the corresponding aldehydes (40-50% over-all). ... 

A - -Steroid. Dauben and Fullerton chose the following route for conversion of A -androstenc-.3)S,17 -diol diacetate (1) into A - -androstadiene-3, 17 -diol diacetatc (4). The starting material was converted into the 7-ketonc (2) by oxidation with chromium trioxide-pyridine complex in methylene chloride (2, 74 75). The ketone OAc... 

Attention may be drawn to a new reagent, chromium trioxide in pyridine, that is said to oxidize primary alcohols to aldehydes. The potential importance of its application to bicyclic diacetals with free terminal groups is clear, both as a preparative method for aldoses and as a means of assigning conformations. 

Solutions of chromium bis(ethylenediamine)diacetate complex in methanol are capable of reducing simple a,p-unsaturated ketones to the corresponding saturated ketones. Useful yields are obtained provided a proton donor (AcOH) and a good hydrogen donor (BuSH) are present in the reaction mixture (Scheme 16). ... 

In the presence of acetic anhydride, acetic acid, and sulfuric acid, chromic acid (chromium trioxide) converts o-nitrotoluene and p-nitro-toluene into the corresponding nitrobenzaldehyde diacetates, from which the aldehydes are obtained on hydrolysis (equation 174) [547, 548, 549. ... 

The formation of chromium(iii) complexes of ethanolamine-NN-diacetic acid in aqueous solution has been investigated by potentiometric and colorimetric methods. A1 1 complex is found to be formed in the pH range 3—6. At pH > 6 hydrolysis takes place. Isolation of mono-, di-, and hetero-nuclear Cr chelates of ttha (ttha = triethylaminetetra-aminehexa-acetic acid) has been accomplished. No evidence for exchange coupling was found for either the dinuclear complex or for the heteronuclear Cr, Cu complex, CrCu(Httha)2,7H20. ... 

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