1,7-Electrocyclizations of Azomethine Ylides: Scope and Synthetic Aspects

Abstract

The 1,3-dipolar cycloaddition of azomethine ylides is a versatile and efficient tool for the construction of five-membered nitrogen heterocycles. When the azomethine ylide is conjugated with double bonds other pericyclic pathways become available, including 1,5- or 1,7-electrocyclizations, with the latter 8π-electron process having only recently emerged as a potentially useful method for the formation of seven-membered heterocycles. Under special structural circumstances, multistep rearrangements can also be observed. In this account, a summary of our work on the exploration and development of 1,7-electrocyclizations of azomethine ylides is presented. 1 Introduction 2 Electrocyclizations 2.1 Reaction of β-Phenylcinnamaldehyde with Amino Acids: The First 1,7-Electrocyclization of Nonstabilized Azomethine Ylides 2.2 Synthesis of Azepines from Unsaturated Aldehydes and Sarcosine via 1,7-Electrocyclizations 2.3 Electrocyclizations of Stabilized Azomethine Ylides 2.4 Electrocyclizations of Azomethine Ylides onto a N=O Double Bond 3 Conclusions