With benzeneselenic anhydrid

The inverse procedure, double bond tritiation followed by re-oxidation, allows for the tritium labeling of a,/8-unsaturated carbonyl compounds (Figure 10.7). Applied to the complex steroid 22 it provided [ H]25, in which 95% of the tritium was located at C2. If most tritium in the intermediate 34 had been on the a-face and equally distributed between Cl and C2, in analogy with the preparation of [ C]24 under very similar conditions, then the benzeneselenic anhydride-mediated dehydrogenation must have constituted a net la,2)3 elimination. This selectivity is consistent with the DDQ dehydrogenation of [la,2a- H]androst-4-ene-3,17-dione (36) to give [2- H]androsta-l,4-dien-3,17-dione (2Z) with little tritium at Cl, and DDQ dehydrogenation of [l)3,2)3- H]testosterone 1381 to provide mainly 17)3-hydroxy[l- H]androsta-l,4-dien-3-one (39) . 

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