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The self‐acylation of 1‐adamantylacetic acid (1) in trifluoroacetic anhydride, catalyzed by triflic acid, proceeds through the formation of the mixed 2,4‐bis(1‐adamantyl)acetoacetic–trifluoroacetic anhydride 2, and it was used as an efficient approach to previously unknown 2,4‐bis(1‐adamantyl)acetoacetic acid (3), its esters 4–6 and amides 7–11, and the sterically hindered 1‐adamantyl(1‐adamantylacetyl)ketene (12). The latter is stable in solution and can be isolated as a neat solid. Addition of methanol or primary amines to 12 gave the corresponding derivatives of acid 3. Acid 3 was decarboxylated to 1,3‐bis(1‐adamantyl)acetone (22), whereas theheterocyclization of phenyl ester 6 with thiourea gave two isomeric adamantylated thiouracils 23 and 24. The structures of N‐benzylamide 7 and thiouracil 23 were confirmed by single‐crystal X‐ray analysis. The utilization of the self‐acylation method for the conversion of some other aliphatic acids is discussed and preliminarily tested.

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