Diversity-oriented synthesis of azaspirocycles

Multicomponent condensation of N-diphenylphosphinoylimines, alkynes, zirconocene hydrochloride, and diiodomethane provides a rapid access to omega-unsaturated dicyclopropylmethylamines. These novel building blocks are converted into heterocyclic 5-azaspiro[2.4]heptanes, 5-azaspiro[2.5]octanes, and 5-azaspiro[2.6]nonanes by means of selective ring-closing metathesis, epoxide opening, or reductive amination. The resulting functionalized pyrrolidines, piperidines, and azepines are scaffolds of considerable relevance for chemistry-driven drug discovery.