Bi(OTf)₃‐Catalysed Access to 2,3‐Substituted Isoindolinones and Tricyclic N,O‐Acetals by Trapping of Bis‐<i>N</i>‐Acyliminium Species in a Tandem Process

New 1,3‐bis‐ N ‐acyliminium species generated easily with nontoxic Bi(OTf) 3 catalyst at very low loadings (2 mol‐%) were trapped inter‐ and intramolecularly with various poly‐nucleophiles. This mild, efficient, practical and general tandem approach provides an array of substituted isoindolinones and cyclic N,O‐acetals.