Powerful approach to synthesis of fused oxa-aza[3.3.3]propellanes via chemoselective sequential MCR in a single pot

A chemoselective synthesis of a unique class of highly functionalized fused heterocyclic[3.3.3]propellane via an efficient sequential one-pot four-component reaction is presented. The syntheses were achieved by reacting ninhydrin with malononitrile to give rise to Knoevenagel adduct, which is trapped in situ by various ketene aminals through conjugate addition and cyclization, providing multifunctionalized unexplored oxa-aza[3.3.3]propellanes. High atom-economy, excellent yields, the simple procedure, no column chromatography, metal-catalyst free, and mild reaction conditions are important features of this protocol.