Novel heterotricyclic systems: 2,6‐dioxa‐ and 2‐oxa‐6‐thia‐10‐azatricyclo‐[5.2.1.04,10] deeanes; 2,6‐dioxa‐11‐azatricyclo[5.3.1.04,11] undecane; and 9,13‐dioxa‐14‐azatetracyclo[6.5.1.02,7.011,14]tetradeca‐2,4,6‐triene

Abstract The acid‐catalyzed condensation of 2‐amino‐1,3‐propanediols and 1,4‐diketones under water‐azeotroping conditions has led to the first synthesis of the new tent‐like, essentially strain‐free heterotricyclic system, 2,6‐dioxa‐10‐azatricyclo[5.2.1.04,10]decane. Over thirty new compounds containing this system are reported. In cases where the aminodiol is unsubstituted or bears a phenyl substituent a mixture of the tricycle and the isomeric pyrrole resulted. These observations indicate alternative pathways in the Knorr‐Paal condensation which lead to one, or the other, or both of these products. A scheme postulating common intermediates is presented. Examples of three additional, related, novel heteropolycyclic systems synthesized in analogous fashion are also reported.