Novel and efficient synthesis of fused spiro piperidone-cyclopropanes from cascade reaction of 1-acylcyclopropanecarboxamides and polarized olefin

We report here that a series of O-bridged ring fused spiro piperidone-cyclopropane derivatives 3 can be constructed in a single step by the one-pot reaction of 1-acylcyclopropanecarboxamides 1 with polarized olefin 2a (EWG = CHO) via the domino process involving [4+2] annulation/intermolecular electrophilic addition/intramolecular cyclization. Furthermore, reactions of 1 with polarized olefin 2b/2c (EWG = CN, COOMe), leading to spiro piperidone-cyclopropane derivatives 4 or 5 by base catalysts selection, were also presented.