Simple ketone starting materials with a halide leaving group and an alkene were prepared
in one step and heated with glycine or glycine esters to promote a tandem imine formation,
cyclization, and dipolar cycloaddition cascade. The chemistry was also feasible with
acetylhydrazide. In each case a single stereoisomer of the tricyclic amine or pyrazolidine
product was formed and the stereochemistry was verified by single crystal X-ray diffraction.
When the reaction with glycine, which occurs with loss of CO2, was unsuccessful, the cascade process could be promoted by cross metathesis to give
the vinyl sulfone starting material that provides a more reactive dipolarophile. Reductive
cleavage of the pyrazolidine gave a spirocyclic diamine product.
Key words
amines - cyclization - cycloaddition - diastereoselectivity - spiro compounds
