An Efficient Regioselective Halogenation of 5-Amino-endo-tricyclo[5.2.1.02,6]deca-4,8-dien-3-ones.

An effective regioselective halogenation of 5-amino-endo-tricyclo decenyl enaminones 6 using N-halosuccinimides is reported. The reaction is extremely fast and the yields are almost quantitative. Exclusive α,N-dihalo or α,γ-dihalo compounds can be obtained by tuning the reaction conditions. Facile transfer of bromine from α,N-dibromo enaminones 8 has been observed. A rationale for the formation of the various halogenated products is presented. The α,γ-dihalo enaminones allow further functionalisation of the tricyclodecadienone system and thus are promising precursors for pharmacologically interesting halo-cyclopentanoids. More importantly, the otherwise more reactive norbornene double bond remained intact under these halogenation conditions.