General Approach toward Aspidospermatan-Type Alkaloids Using One-Pot Vilsmeier-Haack Cyclization and Azomethine Ylide Cycloaddition

The development of a new one-pot reaction sequence afforded the tricyclic core of several aspidospermatan-type alkaloids from a linear, densely functionalized substrate. The key sequence features a highly chemoselective formamide activation that triggered a Vilsmeier-Haack cydlization, followed by an azomethine ylide generation and intramolecular cycloaddition. The choice of nucleophile, azomethine ylide precursor, and dipolarophile was crucial to the success of the sequence.