Steroids and Steroidases. XIV. Studies on the Reactions of 2-Lithio-1,3-dithianes with Steroids Possessing Spiroepoxide Functions at C-3²

Abstract

The scope of the reactions of lithio-dithianes with spiro-epoxides for various stereospecific functionalizations of alicyclic systems has been illustrated by their application to spiro-3a-and -3b-oxiranes of the Sacholestane and Sa-androstane series.La portee des reactions entre les lithio-dithianes et les epoxydes spiranniques pour fonctionnaliser de faqon stertospecifique les systimes cycliques a ete illustree par des applications sur les oxirannes-3a et 38 spiranniques dans les series Sa-cholestane et Sa-androstane.Canadian Journal of Chemistry, 50, 1407Chemistry, 50, (1972 The reactions of a 2-lithio-1,3-dithiane anion with appropriate 1,2 epoxides have been demonstrated to provide a versatile, convenient, and flexible method for the stereospecific introduction of substituents into the steroid nucleus (la, c). The facility with which such reactions occurred encouraged us to explore the scope of lithio-dithiane-epoxide reactions further and the investigations have now been successfully extended to spiro-epoxides.The ease with which spiro-epoxides would undergo reaction with dithiane anions, and establishment of the stereochemical integrity of the reactions, were evaluated on the readily available spiro-3a-and -3p-oxiranyl-5a-cholestanes 1 and 4. The synthetic sequences followed are outlined in Scheme 1.Treatment of 5a-cholestan-3-one with dimethylsulfonium methylide according to the literature procedure (2) gave a 95% yield of a mixture of 1 and 5 in the ratio 3:2. Although pure samples of 1 and 5 had not been obtained by this method in the previous work (2), it was found that separation of the two epimers could be effected by careful preparative layer chromatography (p.1.c.). The supply of the 3a-oxide 1 was augmented by its preparation in 80"/,ield from the 5a-cholestan-3-one-dimethylsulfoxonium methylide reaction (2) and in view of the more ready availability of the latter oxide, the initial experiments were carried out on the sequence of reactions involving compounds 1-4.When the 3a-epoxide 1 was kept with 2-lithio-1,3-dithiane in tetrahydrofuran at 0" for 2 days, the spiro-epoxide ring opened smoothly to give For personal use only.

Ammonium Formate/Palladium on Carbon: A Versatile System for Catalytic Hydrogen Transfer Reductions of Carbon-Carbon Double Bonds

“…22 In accord with previous data, 23 the trisubstituted D 5 -double bond in compounds 19 24 and 25 was found unreactive, as was the highly hindered D 8double bond in lanosterol (28). The The reduction of vinyl-and allyl-substituted steroids, 17 30 and 19, gave the respective saturated compounds 18 31 and 20, 32 with excellent, practically quantitative yield. Also other compounds having allyl residues attached to an oxygen or nitrogen atom were easily hydrogenated, as proved by the hydrogenation of benzylallyl ether (13) 33 to 14 33 and N-allylpyrrolidinone (7) 34 to compound 8.…”