Chemo- and diastereoselective synthesis of new oxa[3.3.3]propellane via a domino cascade four-component reaction based on diketene

A highly convergent, eco-friendly and straightforward synthesis of new O-fused heterocycles, functionalized indeno1,2-b]furan derivatives was successfully accomplished through a one-pot four-component cascade reaction involving, ninhydrin, malononitrile, diketene and various primary amines in the presence of a catalytic quantity of triethylamine in ethanol at ambient temperature, in one pot fashion. This new efficient cascade reaction generates two rings by the simultaneous construction of C-N (one), C-O (two) and C-C (two) multiple bonds, presumably through a sequence of Knoevenagel reaction/Michael addition/intramolecular O-cyclization and imine-enamine/keto-enol tautomerization. The merits of this protocol are highlighted as utilization of inexpensive commercially accessible starting materials, operational simplicity, atom economy, clean reaction profile, simple work-up procedure being conducted at ambient temperature in relatively short reaction times, preventing chromatographic purification, giving excellent yields, and tolerance to a wide variety of functional groups.