Preparation of ring labelled adamantane derivatives II. 2‐adamantanone‐2−14C, adamantane‐2−14C and 1‐methyladamantane‐2 or 4−14C

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AbstractA high‐yield, relatively simple synthetic route leading to incorporation of 14C into the secondary position of the adamantane nucleus is described. The synthesis was achieved by the sequence shown in Figure 2. The key steps involved the introduction of a 14C label by diazomethane‐14C ring expansion of adamantanone to give 4‐homoadamantanone‐4−14C (I). Benzylic acid rearrangement of the corresponding homoadamantane diketone (II) gave hydroxy acid (III) which was converted by a novel reaction (SOCl2/benzene) to 2‐adamantanone‐2−14C (IV). The overall yield of labelled 2‐adamantanone was 66%. Wolff‐Kishner reduction of (IV) gave adamantane‐2−14C (V). This was converted to the l‐methyl derivative (VII) by treatment of the corresponding bromide (VI) with methylmagnesium bromide.