Urotropine Isomer (1,4,6,10-Tetraazaadamantane): Synthesis, Structure, and Chemistry

The
first synthesis of 1,4,6,10-tetraazaadamantane, the C3v-symmetrical structural isomer of urotropine (1,3,5,7-tetraazaadamantane),
and a series of its derivatives is reported. X-ray and quantum-chemical
studies revealed remarkable distinctions in structures of urotropine
and “isourotropine” cations, probably arising from different
types of hyperconjugation between lone electron pairs of nitrogen
atoms and σ*C–N orbitals in these heterocage
systems. Since substitution at bridge and bridgehead nitrogen atoms
can be easily introduced, 1,4,6,10-tetraazaadamantane may be considered
as a new rigid multivalent (3 + 1) scaffold for the design of functional
molecules and materials.