Two strategies have been developed for the synthesis of 2,2,4,4,6,6-hexanitroadamantane
(HNA). Both strategies used the readily available diethyl malonate and paraformaldehyde
as the starting materials, and utilized acylation followed by intramolecular aldol
condensation to construct the adamantane skeleton. The clean nitration to introduce
the gem-dinitro groups onto the adamantane skeleton was conducted using dinitrogen pentoxide
in refluxing dichloromethane in the presence of urea and 4 Å molecular sieves. The
acetylation route was accomplished via 12 steps and afforded HNA in an overall yield
of 4.7%, and the formylation route was achieved via 11 steps in 14% overall yield.
Key words
total synthesis - cage compounds - acylations - aldol reactions - cyclizations