82 Polynitropolycycloalkanes
Dave and co-workers^33 have reported a successful synthesis of 2,2,4,4-tetranitroadamantane
(117) which uses the mono-protected diketone (113) as a key intermediate. In this synthesis
(113) is converted to the oxime (114) and then treated with ammonium nitrate and nitric acid in
methylene chloride to yield thegem-dinitro derivative (115). This nitration-oxidation step also
removes the acetal-protecting group to leave the second ketone group free. Formation of the
oxime (116) from ketone (115), followed by a similar nitration-oxidation with nitric acid and
ammonium nitrate, yields 2,2,4,4-tetranitroadamantane (117). In this synthesis the protection
strategy enables each carbonyl group to be treated separately and thus prevents the problem of
internal nitroso dimer formation.
Br
119BrBr BrNO 2NO 2NO 2
120O 2 NBr 2 , AlBr 3 4 steps118Figure 2.25Sollett and Gilbert^34 reported the synthesis of 1,4,6,9-tetranitrodiamantane (120) using an
identical strategy to that used for the synthesis of 1,3,5,7-tetranitroadamantane. It is worth not-
ing that chemists at ARDEC have made significant contributions in the field of polynitropoly-
cyclic hydrocarbons. An interesting theoretical study using thermodynamic calculations was
used to predict the properties of various caged polynitroalkanes and to determine the number
of nitro groups needed in these compounds for optimum performance.^35
2.8 Polynitrobicycloalkanes
2.8.1 Norbornanes
O 2 NO 2 NNO 2NO 2NO 2
NO 2121Figure 2.26Polynitro derivatives of norbornane have been explored as a class of energetic materials.
Of particular interest in this area are derivatives like 2,2,5,5,7,7-hexanitronorbornane (121),
which has an excellent carbon to nitro group ratio. At present, only the 2,2,5,5-tetranitro (127)
and 2,2,7,7-tetranitro (136) isomers of norbornane have been synthesized, with the hexanitro
isomers remaining elusive.