Conformationally constrained 1,4-DHPs. A convenient route to bis-1,4-DHPs as a novel class of nitrogen compounds

2-Formyl-1,4-DHP derivatives undergo the tandem Knoevenagel condensation/amino-nitrile cyclisation with activated methylene reagents to afford high functionalised indolizines. However, in the absence of this tandem, the Knoevenagel condensation intermediate leads to bis-1,4-DHPs as a new class of nitrogen compounds.