. Can. J. Chem. 60, 1919Chem. 60, (1982. Treatment of A4-3-ketosteroids with rerr-butyl hydroperoxide in the presence of lithium hydroxide leads to the formation of the corresponding 4P,5P epoxides stereospecifically and in good yield. The stereospecificity of this reaction is explicable in terms of the accepted mechanism for the hydrogen peroxide epoxidation of A4-3-ketosteroids.The use of aqueous sodium peroxide as oxidant leads to the production of the corresponding A4-3,6-diones. A mechanism for this reaction is proposed in which the key step is autoxidation of the corresponding deconjugated A5-3-ketone, produced from the starting material in situ by the action of the reagents. Lithium peroxide does not oxidize androst-4-ene-3,17-dione at C-6, but produces the 4,5 epoxides in low yield together with an A-nor-3,5-secoacid.HERBERT L. HOLLAND, ELLY RIEMLAND et ULRICH DAUM. Can. J. Chem. 60, 1919Chem. 60, (1982. Les A4 ctto-3 sttro'ides rtagissent avec I'hydroperoxyde de rerr-butyle en prtsence d'hydroxyde de lithium en donnant sttrtospecifiquement les tpoxydes 4P,5p correspondants avec un bon rendement. On peut expliquer la sttrtosptcifitt de cette reaction en fonction du mtcanisme accept6 pour I'tpoxydation des A4 ctto-3 sttro'ides par le peroxyde d'hydrogtne.L'utilisation du peroxyde de sodium en solution aqueuse comme oxydant conduit a la formation des A4 diones-3,6 correspondantes. On propose, pour cette rtaction, un mtcanisme dans lequel l'ttape fondamentale est I'auto-oxydation de la AS-cttone-3 dtconjugute correspondante, obtenue in siru a partir du produit de dtpart sous l'action des reactifs. Le peroxyde de lithium n'oxyde pas I'androsttne-4 dione-3,17 en position C-6, mais il conduit I'tpoxyde-4,5 avec un faible rendement en m&me temps qu'h un acide A-norseco-3,5.[Traduit par le journal]The epoxidation of a,P unsaturated ketones by basic hydrogen peroxide is a reaction which is tolerably well understood. Its mechanistic (1, 2) and stereoelectronic (3) requirements have been formulated, and, in the case of A4-3-ketosteroids (1) o (3) substituted products have been discussed (4-6).o @ the details ofthe reaction leading to both P (2) and aThe predominance of the P isomer in the latter case c R = OH, aH c R = POH, aH is consistent within the known preference forattack from the p face at C-5 (4b) and intermediates for the formation of a and p products as shown in by Henbest and Jackson (5,6). tert-Butyl hydroperoxide is known to epoxidize certain a,P unsaturated ketones in the presence of base (7,8), but under the conditions employed (Triton B in benzene), was not reactive towards HO A4-3-ketosteroids (7). In the present study, we have do 5HO & obtained good yields of only P epoxide (2) from 6 treatment of A4-3-ketosteroids (1) with tert-butyl ~~b l~ 1. control experiments (~~b l~ 1) indicate hydroperoxide and lithium hydroxide in ethanol that the substitution of lithium hydroxide for sodisolution. These experiments are summarized in um hydroxide when using hydrogen peroxide as 'Author to whom correspo...