Oxazepine Synthesis by Copper-Catalyzed Intermolecular Cascade Reactions between O-Propargylic Oximes and Dipolarophiles

The design and implementation of cascade reactions is a challenging facet of organic chemistry, yet one that can impart striking novelty, elegance, and efficiency to synthetic strategies. The application of cascade reactions to natural products synthesis represents a particularly demanding task, but the results can be both stunning and instructive. This Review highlights selected examples of cascade reactions in total synthesis, with particular emphasis on recent applications therein. The examples discussed herein illustrate the power of these processes in the construction of complex molecules and underscore their future potential in chemical synthesis.

This critical review intends to familiarize the reader with the essence of pi-acid catalysis, in particular with reactions or reaction cascades effected by gold and platinum complexes. Even though materialized in apparently different reactivity modes, such noble metal catalyzed processes can be easily rationalized on the basis of a uniform mechanistic scheme that is outlined in detail. The resulting increase in molecular complexity is illustrated by selected natural product total syntheses and the formation of various intricate non-natural compounds (106 references).