Recent Applications of Imines As Key Intermediates in the Synthesis of Alkaloids and Novel Nitrogen Heterocycles (Report‪)‬

INTRODUCTION Imines and their derivatives have long been recognized as key intermediates for the synthesis of nitrogen heterocycles, especially in the arena of alkaloid synthesis [1]. Over the years, we have had a keen interest in developing new applications of imine chemistry that enable the facile construction of the nitrogen heterocyclic frameworks found in alkaloids and other biologically active nitrogen heterocycles [1]. We have recently reported two novel strategies for the rapid synthesis of bicyclic and tricyclic nitrogen heterocycles that feature cascade and multicomponent reactions (MCRs) involving imines. In designing the first, we were guided by an interest to combine the reactivity modes of imines as both electrophiles and nucleophiles with the nucleophilic reactivity of allylsilanes to provide access to nitrogen heterocycles with nitrogen atoms at one of the bridgehead positions [3]. In the second, we sought to develop MCRs that would provide suitably functionalized intermediates that could undergo cyclization via a number of reaction manifolds [4]. Recognizing that the test of any new methodology lies in its application to practical problems, we successfully applied these processes to the concise syntheses of ([+ or -])-epilupinine (1), ([+ or -])-tashiromine (2), (-)-epimyrtine (3), and ([+ or -])-roelactamine (4).