[4+n] Annulation Reactions Using ortho-Chloromethyl Anilines as Aza-ortho-Quinone Methide Precursors

Aza-ortho-quinone methides are important reactive intermediates that have found broad applications in synthetic chemistry. Recently, 1,4-elimination of ortho-chloromethyl aniline derivatives has emerged as a novel, powerful and convenient method for aza-ortho-quinone methide generation. This review will highlight the recent applications of aza-ortho-quinone methide precursors in annulation reactions to access various biologically important nitrogen-containing heterocycles. The general mechanisms are briefly discussed as well. 1 Introduction 2 [4+n] Annulation Reactions Using ortho-Chloromethyl Anilines as Aza-ortho-Quinone Methide Precursors 2.1 [4+2] Annulation Reactions 2.2 [4+1] Annulation Reactions 2.3 [4+3] Annulation Reactions 3 Conclusion and Perspective