Unprecedented N(H)-bridged tetraaza[1.1.1.1]m,p,m,p-cyclophanes

The first uncatalyzed preparation of tetraaza[1.1.1.1]m,p,m,p-cyclophanes (symmetrical and unsymmetrical) gave access to previously unknown N(H)-bridged derivatives that could be further substituted. NMR studies and theoretical calculations show that these macrocycles adopt an 1,3-alternated conformation.