Asymmetric Cascade Assembly of 1,2-Diaza-1,3-dienes and α,β‑Unsaturated Aldehydes via Dienamine Activation

A cascade vinylogous 1,6-Michael addition/1,4-proton shift/aza-Michael addition/hemiaminal formation sequence of 1,2-diaza-1,3-dienes and β-substituted 2-butenals has been developed under the influence of dienamine activation of a chiral secondary amine. This method exhibits high regio- and chemoselectivity and provides an efficient and straightforward approach to bicyclic l,8-diazabicyclo[3.3.0]­octane skeletons with a tetrasubstituted stereogenic center with fair to excellent enantioselectivity.