Novel aza-Prins cyclization and [3+2] dipolar cycloaddition toward N-heterocyclic molecules and studies toward the total synthesis of borrecapine.

摘要

Highly functionalized 5 or 6-membered nitrogen-containing heterocyclic moieties are highly prevalent in pharmaceuticals reagents, alkaloid natural products, organocatalysts, as well as useful building blocks in organic synthesis. Novel approaches to synthesizing these structures are sought therefore to maximize their accessibility. Within the well-established organic synthesis artillery, electrocyclic reactions serve as the predominant strategy to construct pyrrolidine and piperidine analogues. In this dissertation, the first stereocontrolled assembly of indolizidines from 2-allylic proline esters by aza-Prins reaction, and endo-selective synthesis of highly functionalized 5-vinylic pyrrolidines from benzylic and allylic azomethine ylide using novel [3+2] dipolar cycloaddition are described. These methodologies then culminate in a formal synthesis of Borreria alkaloid, borrecapine, by using an unprecedented sulfonyl group substituted dipolarophile. Finally, new directions in our laboratory to make pyrrolidine scaffolds are included in the last chapter of this thesis.