A heterocycle-forming double Michael reaction. [5 + 1] Annulation route to highly substituted and functionalized piperidines

(equation presented) Z = (at least one), CO₂Et, NO₂, Me; R = Me, CF₃CO. Nitrogen-containing tethered diacids, easily prepared by reductive alkylation of diethyl aminomalonate or ethyl cyanoglycinate, undergo double Michael reactions with 3-butyn-2-one to give highly functionalized and substituted piperidines (pipecolic acid derivatives) with surprisingly high stereoselectivity. The heterocyclic double Michael adducts can be induced to undergo further cyclizations to give a variety of azabicylic and diazabicyclic compounds.