Trienones, steroid

An interesting competition experiment was conducted on the steroid trienone (25), where the possibility for conjugate addition existed in three separate sites in the same molecule, C-l, C-5, and C-7 (equation 29). The catalytic reagent, MeMgl/Cul, gave only addition at C-l.76... 

The trienone (74), either by reaction with diazomethane and pyrolysis of the derived pyrazoline or by treatment with dimethylsulphoxonium methylide anion, yielded28 the 1 a,2 -methylene derivative (75). Epoxidation followed by the action of hydrogen chloride gave (77). The methylene bridge was re-formed by the reaction of collidine, the product being (76). Halogenated steroids of use in determining the metabolic fate of 16-chloro-oestrone methyl ethers and of chlormadinone acetate have been synthesized.29... 

Irradiation of the 5,7-diene gave the previtamin, which was isomerized and saponified to give la-hydroxy-vitamin D3. For the last synthesis of la-hydroxy-7-dehydrocholesterol recorded here, cholesta-l,4,6-triene-3-one was again used as starting steroid.122 Deconjugation of this trienone with strong base followed by immediate reduction with calcium borohydride led to the unstable 3/3-hydroxycholesta-l,5,7-triene which, without isolation, was converted into the 1,4-addition product (265) upon reaction with 4-phenyl-l,2,4-triazoline-3,5-dione. 

Irradiation of the steroid trienone 167 (Chart 28) in dioxane led quantitatively to the bicyclohexenone 168 which, in turn, was further converted into the trienone 170 as the only detectable photoisomer. The second step illustrates the failure of the olefinic carbon 9 to migrate (cf. intermediate 169). In the bicyclohexenone 33d (cf. intermediate... 

Steroid synthesis. The cobalt-catalyzed cooligomerization of a 1,5-hexadiyne (1) with bis(trimethylsilyl)acetylene (2) has culminated in a synthesis of the estra-trienone 4. The cyclization results in formation of the desired Irons, anti, trans arrangement of the B, C, and D rings, probably for steric reasons. The reaction... 

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