Substituted Diazatetracyclo[4.4.0.13,10.15,8]dodecanes as Stable Caged Proton Sponges

Herein, we report a molecular framework design differing significantly from the traditional topology of proton sponges. We developed a synthetic approach to the preparation of caged secondary amines by acid-catalyzed rearrangement of fused tetracyclic heterocycles synthesized by intramolecular criss-cross cycloaddition. Alkylation of amines led to air nonsensitive diazatetracyclo­[4.4.0.13,10.15,8]­dodecanes (DTDs) with rare alicyclic scaffolding in high overall yields. Their pKBH+ values were determined by transprotonation experiments as well as their sensitivity toward nucleophiles, acids and bases. Crystal structures of free base and monoprotonated form are discussed.