Chromic acid-dimethylformamide

Snatzke has found that a solution prepared from chromium trioxide and dimethylformamide with a small amount of sulfuric acid has similar chemical properties as the Sarett reagent. It is useful with acid sensitive compounds and oxidation occurs at such a moderate rate that selective oxidations are often possible. Although the position allylic to a A -double bond is not attacked, the 3-hydroxy-A -system cannot be oxidized satisfactorily to the cor- 

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III. Chromium VI Reagents / 227 Chromium Vi-acetic acid / 227 Chromium Vl-acetone / 228 Chromium trioxide-pyridine complex / 229 Chromic acid-dimethylformamide / 231 Two-phase oxidations / 232... 

Oxidations with chromium trioxide (chromic oxide or chromic anhydride) and with chromic acid are carried out in different solvents, usually by adding solutions of chromic oxide or chromic acid to the solutions of the alcohols. When chromium trioxide dissolved in 80% acetic acid is added to a stirred solution of cis-2-phenylcyclohexanol in acetic acid at 50 °C and the mixture is allowed to stand at room temperature for 1 day, an 80% yield of 2-phenylcyclohexanone is obtained [576], Other solvents used are dimethylformamide [542], hexamethylphosphoric triamide (HMPA) [543], acetone [578, 5 i], ether [55 ], dichloromethane [555, 617], and benzene [571] (equation 249). 

Chlorotrifluoromethylcarbene, 223 N-Chlorourethane, 60, 61 AM-Cholestadiene-3,6-dione, 60 5a-Cliolestane-3,6-dione, 60 5oCholestane-2a , 3a-oxide, 135 5CfrCholestane-2j3,3(3-oxide, 135 5(3-Cholestanone-3,6-dione, 60 A4-Cholestene-3,6-dione, 60, 65 Al-5/3-Cholestene-3,6-dione, 60 A4-Cholestene-3-one, 98 A4-Cholestene-4-one, 60 -Cholestene-a-epoxide, 116 A5-Cholestenone, 65 Cholesteryl acetate, 35, 171 Cholesteryl acetate dibromide, 40 Chromic acid, 54, 246 Chromic anhydride, 54-57, 150 Chromic anhydride-Acetic acid, 56 Chromic anhydride-Dimethylformamide, 56 Chromic anhydride-Pyridine complex,... 

Chromic(VI) acid Acetic acid, acetic anhydride, acetone, alcohols, alkali metals, ammonia, dimethylformamide, camphor, glycerol, hydrogen sulflde, phosphorus, pyridine, selenium, sulfur, turpentine, flammable liquids in general... 

The 3-keto-84 system is introduced by conventional methods, that is, by oxidation of the 3-hydroxy group to a 3-keto group with chromic oxide. Bromination at the 4-position, and finally dehydrobromination with dinitrophenylhydrazine or with lithium chloride in dimethylformamide were carried out to give acetic acid lip-hydroxy-3,18,20-trione-pregn-4-ene lip,18-lactone 17-oxoethyl ether. 

CrO ,-dimethyfformamide. Chromic anhydride is stirred with a solution of the alcohol (e.g. cholestanol) in dimethylformamide until dissolved and a catalytic amount of sulfuric acid is added. Reaction proceeds at room temperature. Acetonide and ketal groups are not disturbed. 

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