Transformations of 1-[2-(Adamantan-1-Yl)-2-Hydroxyethyl]-1,2,3,6-Tetrahydropyridines by the Action of Trifluoromethanesulfonic Acid

Annulated carbamates are precursors for the ring contraction of the adamantane framework

We report a protocol for the one-pot two-step synthesis of noradamantane methylene amines. The first step is the triflic acid-promoted decarboxylation of adamantane carbamates, which causes rearrangement of the adamantane framework to form noradamantane iminium salts, which are reduced to amines in the second separate step.

Synthesis of noradamantane derivatives by ring-contraction of the adamantane framework

We describe a triflic acid promoted cascade reaction of adamantane derivatives consisting of a decarboxylation of N-methyl protected cyclic carbamates and a subsequent intramolecular nucleophilic 1,2-alkyl shift to generate ring contracted iminium triflates. This reaction expands the family of similar transformations, such as Wagner-Meerwein-, Demjanov-Tiffeneau-, Meinwald- or (semi-)pinacol-rearrangement. It allows the preparation of noradamantane derivatives in a few steps, starting from simple hydroxy-substituted adamantane precursors.