A Systematic Study of the Relationship between Molecular and Crystal Structure among 3,5-Diazabicyclo[2.2.2]octane-2,6-diones

A simple, convergent synthesis of 3,5-diazabicyclo[2.2.2]octane-2,6-diones (bicyclic <i>N</i>,<i>N</i>‘-diacylaminals) has been developed, providing access to a large series of compounds differing only in their substituents at the bridgehead positions. These compounds crystallize in several different forms, but always in such a way that each molecule forms four hydrogen bonds. The sheer number of bicyclic amidals that can be synthesized and crystallized provides an opportunity to elucidate crystal-engineering structure−structure relationship (SSR) principles.