A4-Cholestenone

Subsequently the work of R. F. Merritt clearly established the selectivity of additions of fluorine to double bonds in CFC13 at —78°C in preference to reactions with protons. Merritt and co-workers studied such unsaturated systems as indenes and acenapthenes (83), A4 cholestenone (84), 1,1-diphenyl-ethylene (85), Schiff s bases (86), and acetylenes (87). 

Thioketalization.1 Zinc (or magnesium) triflate is an efficient catalyst for thioke-talization with 1,2-ethanedithiol, particularly in the cases of acid-sensitive ketones and highly hindered ketones (e.g., camphor ethane dithioketal, 99% yield). A4-Cholestenone is converted into the corresponding dithioketal cleanly with zinc triflate, but into a 4 1 mixture of the A4- and A5-cholestenone dithioketals with magnesium triflate. In general, zinc triflate is more effective than magnesium triflate. 

Methyl vinyl ketone — methyl ethyl ketone (>98% yield) A4-Cholestenone —> coprostanene (32 %)... 

Reactions Involving Enols or Enolic Derivatives.—The full account was reported for the dehydrogenation of ketones using benzene seleninic anhydride.77 Further studies were reported on catalysts specific for the isomerization of A5-cholestenone to A4-cholestenone.78... 

Ethoxalyl ketones [after citation of ref. 3]. The direct monomethylation of A4-cholestenone gives 4-methylcho estenone-3-one. Monomethylation at C2 can be achieved by prior condensation at C2 with diethyl oxalate to give the 2-ethoxy-oxalate (2).3a This group evidently stabilizes an enolate anion from (2) favorable for... 

The differences noted in Table I in the hydrogenation of cholestenone and testosterone are probably due to differences in solvent acidity used in each case. This is difficult to check since the acid concentrations used were not always reported. It is further possible that with substrates such as A4-3-ketosteroids the acid concentrations corresponding to the two product distribution breakpoints shown in Fig. 6 are different from those found for octalone hydrogenation. Thus, the change in acidity between alcoholic HC1 and alcoholic HBr could correspond to a change analogous to that found between the two breakpoints in Fig. 6. 

Keto compounds. I. Cholestane-3-one. II. Copro-etane-3-one. III. A4 6-Coprostene-3-one ( cholestenone ). IV. Oxime of cholestenone. V. Cholestenone on 0 1 per cent, neutral KMn04 solution. 

Metabolic inhibitors may fail even where no species selectivity is required. The antimetabolite A4)5-cholestenone, designed to inhibit cholesterol synthesis, illustrates this it blocks the conversion of desmosterol to cholesterol, the final step in this pathway (Fig. 4). The blockade of cholesterol formation, however,... 

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,... 

Oxygenation. Brackman et al.1 found that cupric acetate complexed with an amine (pyridine was used) in the presence of abase such as triethylamine functions as a homogeneous catalyst in methanol for the air oxidation of A5-cholestenone to A4-cholestene-3,6-dione in 75% yield. The reaction is applicable to a,fi- and fi.y-aldehydes and ketones for example ... 

The dissociation constants of the cyanohydrins of 3-, 6-, and 7-ketocholestane, 3-keto-coprostane, a4- and A -cholestenone, and A -, A ( )-, A ( 4). and A 4 ergostene-3-one have been measured. . . "in order to determine the relative reactivity towards addition reactions of a keto group in various positions of the steroid molecule, 88... 

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