Synthesis of Natural Products, Carbocycles, and Heterocycles by Hauser-Kraus Annulation

In this Account, we summarize recent developments in Hauser-Kraus (H-K) annulation with respect to syntheses of natural products and other functionalized, fused, or spiro carbocycles and het-erocycles. Although the classical H-K annulation occurs between a 1,4 -dipolar synthon (a 3-nucleophilic phthalide), and a 1,2-dipolar synthon (a Michael acceptor), alternative modes of annulation, such as [4+4] and [4+1], as well as other reactivities of 3-nucleophilic phthalides that have been reported in recent years, are also covered in this account. 1 Introduction 2 Hauser-Kraus Annulation in Total Syntheses 3 Hauser-Kraus Annulation Methodologies 3.1 [4+2] Annulation 3.2 [4+4] Annulation Followed by Rearrangement 3.3 Michael Addition Followed by E2 Elimination 4 Miscellaneous Reactions 5 Conclusions