ABSTRACT
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 cyclization, 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.
Subject(s)
Alkaloids/chemistry , Azo Compounds/chemistry , Cycloaddition Reaction , Thiosemicarbazones/chemistry , Cyclization , Molecular Structure , Spectrum Analysis/methodsABSTRACT
A series of heterosubstitued alkynes was successfully submitted to the intramolecular carbolithiation of their triple bond. We show that the addition is stereoselective because of the control exerted by the terminal substituent X on the geometry of the transition state. A complementary DFT study suggests that the addition is anti when a strong Li-X interaction occurs.