Aza-[4 + 2] cycloadditions employing catalytically derived N-acyliminium ions.

Herein, we report the development of a novel route to tricyclic lactam products via a facile aza-[4 + 2] cycloaddition of catalytically generated acyliminium ions. Employing a Ca(NTf2)2/nBu4NPF6 catalyst system in low loadings, a range of diverse fused ring systems can be synthesised in predominantly good yields.