5 3-Cholesta-1,3-diene

Deuteration by cyclopropyl ring opening Ijas been used also for the stmcture elucidation of a photolysis product (241) of cholesta-3,5-diene. This bicyclobutyl derivative is very reactive and readily hydrolyzed by aqueous dioxane. When the ring opening is carried out in the presence of deuterium oxide, a deuterium is incorporated in the 4y -position of the resulting 6jS-hydroxy-3a,5a-cyclocholestane (242). ... 

The method of choice for the preparation of cholesta-3,5-diene is treatment of cholesteryl tosylate with potassium /-butoxide in DMSO. The mesylate and chloride react similarly. 

Carbonates and carbamates are reported to be intermediate in stability and easier to prepare than xanthates. " They can conveniently be prepared directly from the alcohol in high yield and give clean conversion to olefins. Cholesta-3,5-diene, for example, can be readily obtained via the phenylcar-bamate (114) or ethylcarbonate (115) of cholesterol. Such esters appear to have been somewhat neglected as synthetic intermediates. 

A photochemical reaction in which the reactant is converted into an isomer. The most common example of such a reaction is photochemical cis-trans isomerization. Another example of photoisomerization is the effect of light on cholesta-3,5-diene. 

PALLADIUM-CATALYZED REDUCTION OF VINYL TRIFLUOROMETHANESULFONATES TO ALKENES CHOLESTA-3,5-DIENE... 

Choiesta-3,5-dienyl trif1uoromethanesulfonate Cholesta-3,5-dien-3-ol, trifluoromethanesulfonate (11) (95667-40-6)... 

ChIoro-5a-cholestane, 332 3/3-Chlorocholest-5-ene, 453 4-Chlorocyclohexanone, 72 3 /3-Chloro-5,6a-difluoro-5a-cholestane, 453 4-Chloro-17a-hydroxy-5/3-pregnane-3,11, 20-trione, 86 Chloroiridic acid, 101 4-Chloro-2-phenylquinazoline, 450 Choice of protecting groups, 375 A/B-cfs-cholanic acid, 228 Cholan-12-one, 36 Cholesta-3,5-diene, 207, 331, 336... 

Preparation of cathylates, 414 Preparation of cholesta-3,5-diene, 331 Preparation of 5 -cholest-2-ene, 343 Preparation of 5a-cholest-3-ene, 347 Preparation of 5a-cholest-6-ene, 354 Preparation of cyanohydrins, 412 Preparation and dehydrohalogenation of a-halo ketals, 301... 

Solv. Ref. C- Cholestan-3-one Dioxane/CHClj [65 a] Cholesta-3,5- dien-7-one Dioxane/CHCl3 [65 a] Cholest-5-en-7-on-3/J-yl acetate Dioxane/CHCl3 [65 a] 2/ ,3/ ,14oc- Trihydroxy- 5/i-cholest- 7-en-6-one Pyridine-d5 [588] a-Ecdysone Pyridine-d3 [588] a-Ecdysone triacetate Pyridine-d5 [588]... 

Palladium-Catalyzed Reduction of Enol Trifluoromethanesulfonates to Alkenes Cholesta-3,5-diene... 

Es ist wahrscheinlich, daB 51 aus der cisoiden, 52 aus der transoiden Kon-formation des Ausgangsmaterials gebildet wird (282). Eine fixierte transoide Anordnung eines 1,3-Diens liegt im Cholesta-3,5-dien (Formel 53) vor. Bei UV-Bestrahlung in Pentan entsteht das Bicyclobutan-Deri-vat 54 (101). 

In 1974, Homberg (1974) reported that the action of bleaching earth on cholesterol in solutions of both synthetic triacylglycerol (TAG) and hexane caused the formation of the dehydration product cholesta-3,5-diene. Subsequently it was reported that bleaching of butterfat resulted in the formation of cholesta-3,5-diene (Roderbourg and Kuzdzal-Savoie, 1979) and the authors proposed that the detection of this artefact could be used to identify refined butterfat. In a review article (Kochhar, 1983), it was reported that several other authors had identified steradienes in bleached vegetable oils and proposed that the detection of these could be used to identify refined oils or mixtures of refined and unrefined oil. 

The official method of analysis of steradienes in olive oil (Commission regulation (EC) No. 656/95) involves saponification of the oil with an internal standard of cholesta-3,5-diene, followed by extraction of the unsaponifiable fraction into hexane. The steradiene fraction is then separated from other hydrocarbons, such as alkanes and squalene isomers, by column chromatography on silica gel. Quantitative analysis is then performed by GC. 

Other workers [358] carried out the acylation of estrogens in acetone and reported the following conditions as optimal for the preparation of tris-HFB-estriol 0.1—0.3 jul of acetone per 1 jug of the substrate and 0.05 ml of HFB anhydride at room temperature for 10 min. The use of a larger amount of another solvent (benzene, methylene chloride, dimethyl sulphoxide, diethyl ether, dioxane) was said to result in the formation of a number of by-products. Poole and Morgan [359], however, stated that the HFB derivatives of some steroids are not thermally stable and that only the decomposition product is detected, e.g., cholesta-3,5-diene is produced from cholesterol. This leads to a considerably lower ECD response, so that the detection limit, which under favourable circumstances can be as low as 0.005 ng, is usually not achieved. As steroids that form unstable HFB derivatives they reported cholesterol, lumisterol, ergosterol, estradiol, pregnanetriol and others. 

Inspection of models shows that the departure of a 3 a-tosylate anion cannot derive assistance from rear attack by the sr-electrons with ring A in its stable chair conformation (12). The alternative conformation (13) which might permit homoallylic participation [34] is highly strained and cannot compete with elimination of the m is-axial 4j8 proton to give cholesta-3,5-diene (14), the major reaction product (see p. 252 for further discussion). 

As already stated (p. 240), sr-bond participation does not occur in the solvolysis of e f-cholesteryl tosylate (i). Whatever the reaction conditions the major product is cholesta-3,5 diene, probably resulting from a normal raws-diaxial elimination with the 4/6-proton. Powerfully nucleophilic reagents like pyridine may also give a little of the g/S-substituted product by an Sn2 process [34], A curious side-reaction observed during buffered methanolysis [y ] or hydrolysis [y6] of efi cholesteryl tosylate has been interpreted as a rearrangement of the classical C(S) carbonium ion (2) by hydride migration from C(4), to give the resonance-stabilised ylic cation (3). The structure of this cation was revealed when the methanoly-... 

The deamination of the allylic 3-aminocholest-4-enes is rather remarkable in that the products are not derived from an intermediate delocalised allylic cation 14) [20]. Other cholest 4-en-3-yl derivatives solvolyse to give the allylic cation (14) irrespective of the original C(3)"Configuration, and the cation affords a characteristic mixture of cholesta-3,5-diene and cholest-4-en-3a yl and -SjS-yl derivatives (p. 381). The 3(S-amine (10), however, gave only cholest-4-en 3 -ol (ii) on deamination, whereas the 3a-amine (12) gave cholesta-2,4-diene (13) [20], Both amines therefore react in the same... 

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